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841

REVIEWS

Preparation of Aryl- and HeteroaryltrimethylsilanesDieter HBICH, Franz EFFENBERGER*Institut f r Organische Chemie der Universitt Stuttgart, Pfaffenwaldring 55,D-7000 Stuttgart 80

This review presents a comprehensive survey of the synthetic meth-ods for aryl- and heteroaryltrimethylsilanes. Their preparation canresult from direct silicon-carbon coupling reactions, from cycload-dition reactions, or through modifkation of silylaromatic or-heteroaromatic compounds by incorporation 01' further functionalgroups or by conversion of substituents al ready present.I. Introduction2. Direct lntroduction of Trimethylsilyl Groups into Aromaticand Heteroaromatic Compounds2.1. Radical Silylation of Aromatic and Heteroaromatic Com-pounds2.2. Nuc\eophilic Silylation of Aromatic and HetcroaromatkCompounds2.3. Electrophilic Silylation of Aromatic and HeteroaromaticCompounds3. Synthesis of Aryl- and Heteroaryltrimethylsilanes via Cy-c\oaddition Reactions3.1. Aryltrimethylsilanes via [2 +2+ 2)Cycloaddition Reactions3.2. Aryl- and Heteroaryltrimethylsilanes via [4 +2)CycloadditionReactions3.3. Heteroaryltrimethylsilanes via [2 +3)Cycloaddition Reactions

1. IntroductionThe use of silicon in organic synthesis is enjoying agrowing popularity due to its various preparative ad-vantages I. The trimethylsilyl group is an especiallygood example in that it has long been applied as aprotective group in the chemistry of peptides, carbo-hydrates, and many other compounds, which can beeasily removed. Moreover, it has advantageous ef-fects on the volatility, stability, and solubility ofcompounds so protected1 On the other hand, thespecific re action of silylated compounds with elec-trophiles (e.g. alkylating or acylating agents) hasbeen only recently systematically investigated. Thereactions of trimethylsilyl enol ethers2 are of specialinterest, because different regio- and stereoselectivityrelations can occur than are encountered in the reac-tions of met al enolates. One dass of compounds,

4. Introduction of Substitucnts into the Nucleus ll f Aryl- amiHeteroaryltrimethylsilanes4.1. Halogenation4.2. lntroduction 01' Sulfur Functions4.3. Introduction of Nitrogen Functions4.4. lntroduction of Phosphorus Functions4.5. Alkylation and Hydroxyalkylation4.6. Acylation4.7. Carboxylation4.8. Silylation4.9. Protonation5. Transformation of Substituents in Aryl- and Heteroaryltrime-thy lsilanes).1. Nucleophilic Exchange of Halides5.2. Functionalization of Carboxylic Acid Derivatives5.3. Functionalization of Hydroxy and Amino Groups5.4. Condensation Reactions5.5. Oxidation Reactions5.6. Reduction Reac!ions5.7. Metal Complexes of Aryl- and Heteroaryltrimethylsilanes5.8. Miscellaneous6. ConcIusions

whose mode of reaction towards electrophiles is es-pecially interesting, is the aryl- and heteroaryltrime-thylsilanes. Since reactivity and selectivity of C Hand CSiR 3 bonds differ significantly, isomers thatare difficult to obtain by conventional electrophilicaromatic substitution (normally deprotonation reac-tions) can, in some cases, be more conveniently pre-pared by desilylation reactions3fYH + E-XR

fY1 E- - ~ ) + HXR

deprotonation rcaction

E-X

desilylatiofi reaction


2/36

842 Dieter Hbich, Franz Efl'enbergerIf desilylation f t ~ a c t i o n s are to be of wide preparativeimportance in the chemistry of aromatic compounds,a simple access to the corresponding aryl- andheteroaryltrimethylsilanes is necessary. Apart froman older Japanese paper4, no review of the prepara-tion of this class of compounds exists. One finds ref-erence to the preparation of arylsilanes 5. 6. 7 only inconnection with general publications on organosili-con compounds.We intend to give a survey of C-trimethylsilylatedaromatic and he:teroaromatic compounds. The litera-ture through 1977 has been reviewed. Compoundswhich carry, be:sides the trimethylsilyl group. othergroup IV substituents (e.g. R 3Sn) are not included,since they undergo electrophilic reactions X at the po-sition bearing the substituent more easily than aryl-trimethylsilanes J .

2. Direct Introduction of Trimethylsilyl Groups intoAromatic and Heteroaromatic CompoundsIn principle, trimethylsilyl groups can be introducedinto aromatic or heteroaromatic compounds in a ra-dical, nucleophilic, or electrophilic manner.2.1. Radical Silylation of Aromatic and HeteroaromaticCompoundsThe silylation of aromatic compounds via free radi-cal processes can be induced thermally, photochemi-cally, or by other radical sources. Aromatic com-pounds react with silicon hydrides in the gas phase at500-850 09 , in the liquid phase under autogeneouspressure at 350--500 09 , and in the presence of perox-ides at 135 cl 10: gas phase condensations 11 and reac-tions via electrical discharge 12 have also been re-ported with silicon halides.Ar-H + H-SiR3

Ar-H + X-SiR3 Ar-SiR 3 + HX

The reactions 01' aryl halides with silicon hydrides inthe gas phase at 500--700" t1 and in the liquid phaseat 350-450 U x also afford arylsilanes. Disilanes thatcan be thermally split into silyl radicals react in thesame wayl4. All these reactions are of high encrgy

1

hv

SYNTlIESjS

consumption, give mixtures of products, and thushave limited laboratory use. Their usefulness is fur-ther reduced because the yield of arylsilanes de-creases with increasing number of methyl groups inthe SiXrresidue. Since the reactants are readily ob-tainable, however, these methods ofpreparation maybe of industrial i mportance.Silyl radicals can also be obtained radiochemically(e.g. yl" eO lb ) and show, in principle, the same modeof reaction with aromatic compounds as those in-duced thermally. U.V.-Irradiation of aryl halides inthe presence of aimethylsilane produces aryltrime-thylsilanes along with other products in variousyields, e.g. phenyltrimethylsilane (11 '+"6) 17 or penta-fluorophenyltrimethylsilane ( 5 3 % ) 1 ~ . Pentauorophenyltrimethylsilane' :HCKat1uorobenzcne (' 8.6 g, 0.1 mol) and trimethylsilane (7.4 g, 0.1mol) are irradiated (U.V. light) with shaking tin 240 h in a 300 mls i l i ~ a tube. The tube is cooled to - 196' prior to opening. Trime-thyltluorosilane is serarated by fractional condensation and the rc-maining liquid is distilled to givc heXl!!7uorobenzene; yield: 9.1 g(49'\,): b.p. 80-82" andpenta!7uorophenyltrimethrl.\ilane:yidd: 6.5 g(53% based on hCKat1uorobenzcne consumed): h.p. J70".Aryltrimethylsilanes are also produced by the U.V.photo ysis of bis[trimethylsilyl]mercury in aromaticcompounds as solvents, though usually only in mod-erate yields I9 ,2!J,21.

X : H, F

hv

Ar-Si(CH313 + (H3ChSiX + Hg + other products

In the photolysis of substituted disilanes 1 [R I =H,CH), f-C4H9 ; R 2, R 3 = H, CH), CbH" Si(CH1hl,reactive intermediates 2 are formed by a (1,3]sigma-tropic rearrangement. In the presence of trappingagents such as 3 [Y =ce CH 2, 0; R4 ,,,, H, CH 3, fC 4H 9;R 5 o=.CH), Si(CH3h C(CH1)C H 2 , etc.] or 4[R 6 =H , Si(CH 3h; R 7 =H , t-C4H9 , Si(CH3h, C6 H5],intermediate 2 undergoes addition reactions to givethe aryltrimethylsilanes 5 or 6, respectively22.In contrast, photo ysis of 1 in the presence of dime-thyl sulfoxide takes a different pathway. Here, the

)


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November 1979products are found to be disiloxanes, arylsilanes[among these are aryltrimethylsilanes (56-57%)], di-methylsilanone, and dimethyl sulfide232.2. Nucleophilic Silylation of Aromatic and Heteroaro-matic CompoundsThe reaction of triorganosilylmetal compounds24with aryl and heteroaryl halides leads to triorgano-silylaromatic compounds.

M = Li, Na, KThe preparative value of this reaction using iso la edtrimethylsilyllithium 25, -sodium25, and -potassium25is limited, due to the instability of these compoundsand to the possibility of a met al/halide exchange(formation of disilanes). This method has gained sig-nificance only through the in situ formation of the si-lylating agents from hexamethyldisilane with appro-priate bases. The reaction of aryl halides 7 with thedisilane in this way gives aryltrimethylsilanes 8 inyields of 63-92%26.

7

X' = H3C, Clx2 = Cl, Sr, JMY = LiCH3, NaOCH3, KOCH3

HMPT )

8

2-Pyridyltrimethylsilane is similarly obtained from2-bromopyridine, the disilane, and potassium me-thoxide in 80% yield26. The exact mechanism is stilluncertain, although an aryne pathway can be ex-cluded because of the distribution of isomers ob-tained. Cleavage of hexamethyldisilane with arylhalides 9 under the catalytic influence of tetrakis[tri-phenylphosphine]palladium(O) affords similar prod-ucts 10. This reaction is especially important for thepreparation of nitrophenyltrimethylsilanes, since thenitro function is destroyed by all other silylatingmethods (Table 1).

9

10

Pd[P(CsHsh].,140-160, 40-90 h )

Preparation of Aryl- and Heteroaryltrimethylsilanes 843'fable 1. Aryltrimethylsilanes 10 via Palladium-Catalyzed Cleav-age of Hexamethyldisilane with Aryl Halides 9Substrate 9 Yield [''


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844 Dieter Hbich, Franz. EffenbergerMethod B: Direct: Performed as abovc except with immediate in-troduction of air after which Ba is isolated by distillation aud re-crystallization; yield: 65%, rn.p. 98".Table 2. Reductive Silylation of Arenes 11 with Lithium/Chloro-trimethvlsilanea in Tetrahydrolilran to 12 and SubselJucntAir Oxidatilln b to 133415 .Su bstrate 11No. R'a Hb H3Cl' H,Cd He ILCf fi leg i-C,H;

R' R1H HH HIhe HH,C tbCH H,CH,C H,CH 11

Yield [%101' 12'60 ~ : 5 673075 ~ ( ) 70 75550

a lJse of magnesium/chloTotrirnethylsilane in hexamethylphos-phoric triamide results in lower (1O25'!{,) yiclds of 12" ".b Only papers which indude this rearomatization step are li,tcd." Yield of 12., 13 almost quantitative in each case.

Naphthalenes and anthracenes do not reaet with me-tals and chlorotrimethylsilane as specifically andusually give poorer yields than the benzene deriva-tives 1131.3X ..


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November 1979Despite this fact, electrophilic introduction of silylgroups into aromatic and heteroaromatic com-pounds is the most important preparative method forthis dass of compounds. However, instead of thearomatic compounds, their considerably more nu-deophilic organometallic derivatives are usually al-lowed to react with chlorotrimethylsilane or similarsilylating agents.2.3.1. Preparations via Organomagnesium CompoundsMany aryltrimethylsilanes have been prepared byconventional Grignard reactions [i.e. defined forma-tion of the Grignard compound and subsequent sily-lation (Table 3). The use of cyanotrimethylsilane orethoxytrimethylsilane 60 instead of chlorotrimethylsi-lane are exceptions.Ar-X + Mg

Table 3. Aryltrimethylsilanes via Conventional Grignard Reac-tionsAr X

O BrOB ro-{}sr

Br

H3C-{}B ri-C 3H7-{}sr

ICzH s13Si -CHz-{}s rIH 3 CI 3Si-CHz-{}Br

Sr0--0

Yie1d[%]

41-92

7660

41

50

80

56

78

80

71

8476

Reference

72-77

7778

70

61

61, 72, 7661, 79

808081

81

81

81

82

Preparation 01' Ary1- and Heteroaryltrimethylsilanes 845Table 3. Continued_._----------------_ ._------X Y ~ d Reference

[%]- - - - -_ ._------_ ._-----H ZC=CH -oCI 70

H3CH2C=b -oCI 71F3 C~ s r 65F3CC l : OB rIH 3C1 3S i - { }C I 60-80s r - { }B r 93'; 52-80

Ar-OH 3 C - ~ i - ~ S r I"=..rAr-O

H3c o - { }B rBr0 0-0

o-0-{}sr

14- 41

36

8642- 81

o -CH2 - 0 - { }B r 88Br -{}CHz-o -CHz-{} s rH3c-s-{}sr 65o-S-{}Br 60IH3ChSi-O-{}Sr 77

C.Hg-/IH3C13Si-0-Qsr 62

C.Hg-/F-{}Br 68-91

F FF ~ s r 35F F

CI6JClhOJ

22-41

45

7590

52

65, 81", 83"

84"

85, 86

8687, 88, 8967', 72, 76, 87,105

90

91

92

93, 94, 95

79697

9462, 63, 64

98

72, 76, 99

18, 100

61, 101

99, 102

61, 91, 103, 10461, 72, 76, 105

106


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846 Dieter Hbich, Franz EffenbergerTable 3. Continued---- -- ---------------_._- . - ._---_ ._ - - - - - -Ar- XC I X ~

Re,Cl ClBrO-Br

Br--(.S),-BrU

Yield1%)

80

50a Polymers of product are also formed.

Refercnce

107

108, 109110, 111

h Several trimethylsilylpolyphenyl ethers are also formed.e Bis[trimethylsilyl) product formcd.

Diethyl ether is usually used as the solvent, althoughtetrahydrofuran is finding increasing use. Since theformation of Grignard function in sterically hin-dered positions (o-silylation) occurs only with difli-culty, the ether can be replaced by some higher boil-ing solvent after the reaction has been started, to af-ford better yields61 FUIlctional groups that reactwith Grignard reagents have to be protected, e.g.phenols by O-silylation62.63.64 or carbonyl groups byacetalization. An example for the preparation of 4-acetylphenyltrimethylsilane (19) is illustrative65 66

1. Mg2. (H3C)3Si Cl3. H$/H20 )

TIH 3 C ~ ' B r

19Haloaryltrimethylsilanes are obtained by selectivesilylation of polyhaloaromatic eompounds, in thecourse of which the different reactivities of C Xbonds (J> Br > Cl> F) towards magnesium are uti-lized. By using an exeess of magnesium and chloro-irimethylsilane it is also possible to achieve bis-silylation 67 ,6x. The introduetion of the trimethylsilylgroups via the trichlorosilyl compounds6 I.o9,70.71 isless often used but is illustrated by the preparaticm ofl-naphthyltrimethylsilane (20)NI.

2. SiCI,- - ~ )

20In so me eases inert aryl halides which do not reactweil under conventional Grignard conditions can beconverted to aryltrimethylsilanes in better yields by

using the entrainment method l12 (du ring the re actionsome alkyl bromide is continuously added as an en-trainer to keep the magnesium surfaee aetive (Table4).Table 4. Silylation 0" Aryl and Heteroaryl Halides via the Entrain-

ment MethudAryl Halide

Ob-B r

60BrfS(;rBr

CH 3cA; rBr

Br,O-OCH2-{}Br

ClO C H 2 ~ "I fiq

BrQ rOS-{}Br

rjB''/ 'NH3C N

' q - { }B 'CH3

Br BrBri : tsr

Br BrO ~ B r < "I0

Entminer

Br-CH2-CH2-Br

Br-CH2-CH 2-B r

Br --CH2'-CH2-Br

Br-CH2-CH 2-B r

Br-CH2'-CH2-Br

Br-CH2-CH2-Br

Br-CH2'-CH2-B r

Br-CH2'-CH2-B r

C2HS-Br

Br-CH2-CH2-B r

C2Hs - Br

Br-CH2-CH 2-B r

C2Hs-B r

Br-CH2--CHcBr

Yield Reference[%)

51 113

10 113

25 114, 115

31 115

116

41 113, 114

21 97

114

50 117

60 114

118

80 119

87" 120

121" - - ' - - ~ - - - - - - - - - - - - - - - - - - _ .. ' - - " ~ - ---" Only thc mnno-,il:'lated product is fnrmed.The separate pn:paration of the organometallie in-termediates is orten accompanied by disadvantages(e.g. isomerizatiern, decomposition, more difficult 0-silylation, ete.). These obstacles are reduced bybringing together the aryl halides with magnesiumand chlorotrimethylsilane in a one pot re:action. Theadvantages 01 ' such an in situ procedure 122 have be-come obvious in the preparations of polysilylatedbenzenes 123 .124 and naphthalcne3 l


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November 1979-quinoline13O Particularly advantageous - even withsterically hindered compounds - is the in situ Grig-nard synthesis of aryltrimethylsilanes in hexamethyl-phosphoric triamide as solvent, as demonstrated by arecent publication wh ich gives a comprehensive sur-vey of the applications and limitations of this proce-dure (Table 5)131.Table 5. In Situ Grignard Synthesis of Aryl- and Heteroaryltrime-thylsilanes from Halides using Magnesium/Chlorotrime-thylsilane/Hexamethylphosphoric Triamide ,,,- - - - - - - - - - - - - - - - ,-------ArylHalideOCIOB,

CH36 CI

t>--O-B'

Yield[%1

8788

80

8581

B3

85

62

49

5B

74

80

6731

77

2-t-Butylphenyltrimethylsilane' ":

ArylHalideF-(}B'CI-(}JF3COB,

O-(}B,O-(}B'C)-CI-BrN ~ B ' )0-Br

Br

Yield[9


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848 Dieler Hbich, Franz EffenbergerTable 6. ContinucdArylHalide

Bro-dB'h IliB'

I l iO CH3OB,

IH3C11N-G-Br[IH3C13Si)1N-G-Sr

Yield[%1

36- 65

75

n b83

71

3640 - 55

30

45

46- 84

29-7953

Reference

134", 138

139

139

140

141

91

91, 141

142

143

91, 143 -146

91, 137, 144, 145147

aHalide used for the preparation of the aryllithium not speci-lied.b Bis[trimethylsilyl] product obtained.3-Dimethylaminophcnyltrimethylsilane 144:To !inely cut lithium (5.6 g, 0.81 mol) suspended in ether (100 ml),a solution of 3-bromodimethylaniline (70 g, 0.35 mol) is aJdedwith stirring over 2 h. The mixt ure is heated under reflux !l)r 30min, then a solution of chlorotrimethylsilane (37 g, 0.34 mol) inether (75 ml) is added over 1 h. Stirring and heating under refluxare continued for 2 h. The reaction mixture is hydrolyzed, the etherlayer separated, and dried with drierite. The mixt ure is !iltered andthe ether evaporated under reduccd pressure. Distillation affords acolourless product; yicld: 56 g (84%); b.p. 1 0 9 - 1 1 O ' ~ 18 torr; n ; ~ ' : 1.5265.Halide/metal exchange reactions present a furtherpossibility for the preparation of aryllithium com-pounds.

Ar-Si(CH313 + LiCI

The discrimination of reactivity of the C X bond(J>BI>CI>F) towald n-butyllithium enables a se-lective exchange with polyhalogenated aromaticcompounds (Talble 7).

SYNTHESISTable 7. Aryltrimeth:tlsilanes via Halogen/Metal Exchange withn-Butyllithil m aud Subsequent Rcaction with Chlorotri-methylsilaneArylHalide

Br60

~ B r

Brro OH" 'I "" ./~ O H

r

QOBrBrmB r ( : x >C'IDyBr

\ 0 ~ ~ B r Sr( j ) j

Yield[%]

30

27

83 "

46

46

58

58

35

20

53

48

70

50

72

67

70

36

Reference

113

148

149

'77

77

77

77

150

150

150

150

151

152

152

152

152

94, 114

48 94

51 94


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November 1979 Preparation of Aryl- and Heteroaryltrimethylsilanes 849Table 7. Continued Table 7. ContinuedAryl Yield Reference Aryl Yield ReferenceHalide [%] Halide [%]

S 6-CH3f5J(;rBr 50-71 94, 153 '/ \ Br 64 97S rl 3C- S- - Br64 - 80 94, 153 65 97

Br5 IHO-CH2-CH22 N

O9) 45 94 '/ \ Br 51 160Br 6-Si ICH3)3

C2HS '/ \ Br 97IN 77 94 IHJChSi - s --Br 20- 80 97, 161Br

Br--0--Br 77a 162'/ \ I" Br 68 115- - d-H2-CH2-NIC2HS!,N '/ \ Br 80 163OBr 24- 39 129, 130, 154CI

{}-Br 37- 39 129, 130 OBr 62 91ro CI CI49 130 CI*CI- "Br 48, 44 a 164, 165, 166aCQ CI CI"- " 36 130 CI CIBr IH 3ChSi*C I 167

OBr CI CI'/ 'N 91, 90" 155, 342 BrBr OBr 17 85, 168O B r Br--Br'/ 'N 69" 342 47-79 145, 169, 170

Br Br0--OBr 37-65 77 33 108BrH3C-D--O- Br 64-78 156, 157, 158

d-0OH

'/ \ Br 57 168H3C 0 - O - O - B r 43 157 CI FCI-O-O-Br

F*,CI 171 b72-80 156, 157 F F

CI Cl F6-o-Br 65 156 F*,CI 87 171 bB,-D--O-Br Cl F43 157 CI Cl CH Cl CIt- C4H9-CH2b- C I * ~ i * C I 17 a 167'/ \ Br 70 159 Cl CI CH3 CI CIt-C 4Hg-CH2- - B, 80 159 *9H3 9 ~ * I '/ \ 5i-O-Si I \ CI 13a 167t - C 4 H 9 ~ - I I -:-CI CI CHl CH3Cl Cl'/ \ J 108

CI-QCI 80 '-C,Hg !. 172H3C0o - CI Cl'/ \ Br 27 108 ., Bis[trimethylsilYll product obtained.H3CO h Use of excess n-butyllithium and chlorotrimethylsilane results in~ . ~ - ~ - - _ . - . - ~ ~ ~ - - - - - - - - - lormation of polytrimethylsilylated products.


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850 Die1:er Hbich, Franz Et1enbergerThe more strongly acidic C H bonds of heteroaro-matic compounds such as, fr example 21, can bemetallated directly by treatment with organolithiumcompounds and subsequently silylated to yield si-lanes 23 without the need for the intermediate halo-genated compollnds (Table 8).

Table 8. Heteroaryllrimethylsilanes 23 via Hydrogen/Metal Ex-change in 21 with n-BlItyllithium and Subsc4uent Silyla-tionSubstrate 21R'HHI f

YooS

zCIIC HrCIIH,C S

(H,C),N-SO, S(C 2H,),N SO, SCHCHCHBrH

(C 1H,OhCIIC ~ , > < C H 3 (C 2H,OhP(0)11II

SSSS

CHCCOOHCHCH

S CHNH CHN CH, N

Yield lW,] Rcference01'23

724179

93963123 403356

lJ417394. 117

175176176173173177177.178179IXO, lXIIX2. 1 ~ 3

a Lithium diisopmpylamide is lIsed as metallating agcn!.

In this manner, 2,5-bis[trimethylsilyl]thiophene(65%) is obtained [rom thiophene 175 by reaction withtwo mol of butyllithium/chlorotrimethylsilane andN-methyl-1 ,4-bis[trimethylsilyl]imidazole (32%) maybe prepared from N - m e t h y l i m i d a z o l e l ~ 2 . This meth-od of silylation is also applicable to benzo-annelatedsystems, e.g. benzothiopheneY4. 114, -thiazole I X4. I X "and -imidazole m . 183 .Trimethyl-( t -methyl.2-imidazolyl)-silane Xl:I-Methylimidawlc (9.5X g. 120 nlIlJol) is ,Iowly addcd (dropwist') toa hexane solution 01 n-blltyllithillm (120 mmol) in ether (150 ml).After hcating under reflux tin I h. chlofotrimethyhilallc ( 1 3 . ( ' . ~ g.120 mmol) is added, After 2 h 01' stirring. the reactioll mixture isliltcrcd. thc solvent t:vaporated. and the silane isolated by vaC'lllmdistillation; yicld: 10 J g (56%): b.p. 92"i 10 torr.

Besides the heterocyclic compounds 21, benzene der-ivatives 24, in which ortho-metallation 1X6 is favouredby appropriate substituents, can also bc metallateddirectly and subseqllently silylated to afti.lrd aryltri-methvlsilanes 2c, (Tahle 9).

SYNTIIESIS

25

26

Table 9. A r y l t r i m c t h ~ lsilanes 26 via orlho- Metallation 01' BcnzeneDerivatives 24Substrate 24 Yidd ('Ii'] ReferenccR' R2 x of 26fI Ii OC"II, 6271 93.94. 114H H SC,,1-I, 23 94. 114F H OCH, 13 187CI H OCH, 60 IR?Hr 11 OCH, 44 187J H OCH, 58 187H H eH, N(CH'll 60 188Ii 11 CO NB (;'.11, 60 189H H qOSi(CH,hl-- CII) 9()" 190H,C H qOSi(CII,J'] CH, 71Lh 190H 11 1e ero ~ i ( C l l ; ) d CH, 90' 190" n-Butyllithium/tetr.lmcthylethylcncdiamine used as metallating

agent.h Two produds arisir g from dimetallation also formed (yield: 1 l\'[)each).

The intramoleClllar complexation of the lithiumcompound 25 is decisive. Since the complexation isalso possible with the other ortho-position, bis-sily-lated compounds, such as 2,2' -bis[trimethylsilyl]di-phenyl ether (609)162 or 2,6-bis[trimethylsilyl]-N,N-dimethylbenzylanine (85%)IXX, can be produced se-lectively. In the cases of phloroglucine trimethyl eth-er 191 , methoxy-m.phthalenes 150, and dibenzofuran94reaction can be brought about specifically. Aromaticcompounds without such C H bonds react to formmixtures of isomers192.116. Thus polymetallation/si-lylation reactions of aromatic compounds such as bi-phenyl, anthracene, fluorene etc. with butyllithiul11/tetramethylethylenediamine/chlorotrimethylsilaneare of no prepara tive importance 13.There is the possi bility of a compet.ition between me-tal/halogen exchange (formation >l)f 28) and metallhydrogen exchange (formation of 29) in the case 01'the polyhaloarOll' atic cnmpounds 27 ('fable t(.Once again polysilylated prmlucts are fonlIed whenan excess of organolithium compound (R : i L i ) / l ~ h l o rotrimethylsilane is employed )4 . 1"1. 190 I')','.


11/36

November 1979 Preparation 01' Aryl- and I-Ieteroaryltrimethylsilanes R5tTable 10. Competition 01' Metal/llalogen and Metal/llydrogcn Exchange in Plllyhaloaromatk Compounds 27-_ . - ~ - - ------ ~ - - - - ~ - - - - - - , - - - - - - - - - - - - - - - - - - -Yield [9,,) 01' RderenceR ' R' R' R 4 X R' 28 29- ~ - - - - - - - ' - " - - - - - - ' - - - - - ' - - - - - ' - - - .- ~ ._---- ._ - - . --- - - " - ~ - - - - ~ ~ - -_ ._-- " - - - - - - _ . _ - - - - - - - . _ - -CI H CI CI CI /-C,H" 100 165, 1')4, 195CI H CI CI CI n-C 4 11" 71 29 165,194, 195CI H CI CI CI C"H, 10 90 165, 194, 195CI H Cl CI CI CII, 7 93 165. 1


12/36

852 Dieler Hbich, Franz Effenberger'fable 11. ContinucdR'

11

H

er.II,H(H,C),Si1111HHH11HH,COHHH(H,C)$iOH11(H,C),SiOH(H,C"SiO

J{'

H(CIl,),(CII,),(nh)4

11C,JLH(H,C),Si111111II,COH,CO 011"HH(1I,C) ,SiOHHC"II.C.II.,

R'

H

t-C,H'iHHH1I11I lH(11,ChSi4-(H,ChSi C,.H,4-Br C,,1I 411H,CO

(CII,ll 0HC"B,., , ,(YC"II,O(H3ClJSi-O-CH-CH, -0 -ICH3HH(JI,C),SiO(11.,ChSiO(H,Cj,SiO11

11 [(lI,C"SibN H- - - " - - - - - - ~ - - -----_. -_ .._--,-. Slldium suspension." Bisltrimethylsilyl/ prnduct f()rmed., n 04,8 , 12, 14. 16. IS.

H

H111111HHHHI !11H11

HH(1I,C),Si1111"11HH11H"1

1- and 2-Chloronaphthalene]12 as weil as variouschloro- and bromophenanthrenes1 l react in a simi-lar way. The partial re action of polyhaloaromaticcompounds is not possible: either all halide atomsreact213 or the molecule does not undergo a Wurtzcoupling61 . Numerous 2,4,6-substituted silylatedphenols have be,;!n prepared according to this meth-Od214 ,21 ' .o-'Joh.ltrimetbvlsilllIlC . :o-Chl;lrotllluel;c (502.5 g. 3,95 mol) is mixed wilh l'hlorotrimeth}lsi-lane (see below) ami added slowly to molten sllJium (11)5 g. 8.5111(1) in hoiling toluenc 1400 mt containing suffkicnt chlorntfllllc-thvlsilane to lowcr tbe reflux tcmperature t(l 102 . A total (lf 475 g(4:4 mol) nf chlorotrimethylsilanc is empillyedl, Thc reaction isvigoro\ls: when the n:action is wmpIete, the rea


13/36

No\cmbcr 1979 I'reparation nf Aryl- and Heteroaryltrimethylsilanes R53Table 12. Trimethylsilyl-Substituted Phenols 35 via Rcarrangemcnt of Metallated Phenoxytrimethylsilancs 33

. _ ~ - - ~ - - - - -

Sub,trate 32R' R 2 R 1 X----------------------- -- . _ - - - - - - - - -

I I 11 2-BrH 11 2-BrH H H 3-BrH H 4-BrH 11 4-BI"H 1I 4-BI"

H,C " 2-BrH,C H 4-BrI-C4H., B 2-BrI-C411 .. 11 2-BrI-C4H., (-C4 11., 2-BrI-C,B" t-C,II., 2-BrBr [-C4 B" 2-BI"Br Br 2-BrBr Br 2-BrI-C4H., (1I,C),si 2-BrH (H,C),Si 2-BrH Br 2-BrI-C 411., Br 2-BrH,C I-C 4 H., 2-BrCI CI 2-BrI-C 4 IL, Br 2-.1

" Yield determined by G.L.C./M.S." Obtained as mixturc with other products.

Repeated application of this process to polyhalo-genated compounds 32 as well as the working up of34with agents other than water provides further prepara-tive possibilities2tX Thio derivatives can undergo rcarrangement to givetrimethylsilyl-substituted thiophenols in the sameway161.97, however, the rearrangement of N-silylatedhaloanilines fails 147.2\(,. The rearrangement methodcan also be used with some pyridines 36 to yield tri-methylsilyl-2-pyridones 37 without difliculties l17(Table 13).

1. f-C.HgLi2. H20 )

36 37

Table 13. Trimethylsilyl-SlIbstituted 2-Pyridoncs" 37 via Rear-rangement of Pyridines 36 using I-BlItyllithilim '17Suhstrate 36R'

HH,CHH

R'11H11H(:.,H,

R'HHHH,C

x3-Br5-Br5-Br5-Br6-Br

Yicld Pi;1nf376251984769

a In the same way, 0- and N-trimethylsilylated pyrimidincs canbc rearranged to the C-silylated compollnds 2",_ 221.

-- - - - _ . _ - ~ - - - - - - ~ - ~ . " - - ~ _ . _ - - - " ~ - -Metallating Yicld [";,1 RcfcrclIl'cagent 01'35

--------- -------_ ..__ ." --_ . . _ - - - - - - - - - ~ - - " - - - - - - - - - - - -,n - C 4 ~ L L i 2()-X6 97. 161. 216t-C,IL,Li 100" 217Mg SO 2U':I/-C 4 IL,Li SO 97.216I-C,I/.,Li 87" 217Mg 17" 21X{-C,IL,lj 93 217t-C,II.,1.i 80 217n-C,H.,Li 96 21'1Mg 80 218II-C 4H.,Li


14/36

854 1}ieter Hbich, Franz EtTenberger3.1. Aryltrimcthylsilallcs via [2 +2+ 21Cycloaddition Rcac-tionsCooligomerization of diynes 38 with acetylenes 39 inthe presence of cobalt catalysts is a general synthesisfor trimethylsilyl-substituted benzocyclobutenes. in-danes. tetralins 40, or naphthalenes 41 (Table 14).

r C: :C- R'y' -C::C-H

38 39

Table 14, TrimethyLilyl-Substituteu Benzocydllalkancs 40 orNaphlhakncs 41 via 12 +2 t 21 Cydoauuitil\n [{caclions

Di}nc ."ill Acetylene Prouuct Yidd [{cfl,r[{' Y ."i9 type I"nl entcR)11 (C1L), (H,C"Si 40 !>o 226(H,C),Si (CH,l, 11 40 12 22711 (CII,) , (l1,C),si 40 51) 22511 (CIU, (11 ,CLS. 40 225H (CH,), fI,e 40 -'4 225lf CII CIf, (lf,C),Si 41 30 22X

OSi(CII,),H CII eil) (I I C),Si 41 30 22xOC/L

11 CII CH, (11 ,O,Si 41 30 22X2-Thp'-_ . _ ~ - ~ " . - -- -- - -. ~ - . - - - - - - - - - - - ~ . _ - - - - - - - - -" Th p = 2-tetrahydropyranyl.

The cyclotrimerization of trimethylsilylacetylenes inthe presence of cobalt catalysts22'J or the system ti-tanium(IV) chloride/trimethylaluminum21o is diffi-cult to direct and nonnally affords isomer mixturesof polysilylated henzenes.

3.2. Aryl- and IIctcroaryltrimethylsilancs vht 14 + 21Cy-c1oaddition R,eal'tionsCycloaddition reactions 01' a-pyrone (42) or tetra-phenylcyclopentadienone (43) with trimethylsilyl-acetylenes 39 lead to aryltrimethylsilanes 44(63%)2:11 or 45 (90%f32, respectively.Very strained systems such as trimethylsilyl-substi-tuted benzocydobutenes and -hutadienes undngo

39

I ~ (42)

SY1-d H E S I ~

45 R' = H, R' : CsHsring-expansion l) n treatment with alkenes and al-kynes to afford letralins226 an d naphthalenes 174 oftypes otherwise n:)t readily obtainable. The additionof 39 [R 1= H, Si(CH,hl tn 3,6-bis[ methoxycarbonyl]1,2,4,5-tetrazine gives C-silylated pyridazines 00-R 5 ~ Y , ) with elimination of nitrogen:"l.3.J. Ilet('roaryltrimcthylsilanes "ia 12 +3JCycloadditionReactiol1sThe pyrazolyltrimethylsilanes 47-49 are readily ob-tained in good ydds by the cycloaddition of tri me-thylsilylalkynes 39 to diazomethane derivatives 46(Table 15).

46 39R3 Si(CH 3b

R2i;)(H3ClJSi R32bN and/orR W"47 48 49

'fable 15. Trimethylsilyl-Substituteu Pyrazoles 4;-49 via [2 +31Cy-c1oaddition R e a ~ t i o l l s _ . ~ _ . _ . _ ~ - - -

I )iazomethane 46 Alkyne 39 Product Yiclu Refer-R' R' R' typ" 1 ~ ' , 1 eil


15/36

November 1979gioselectivity to afford predominantly the pyrazoles48. This is probably due more to steric than to elec-tronic factors 2J4 Using this method, trimethylsilyl groups can also beintroduced via a [2 +3]cycloaddition reaction asshown by the reaction of bis[trimethylsilyl]diazome-thane with acetylenedicarboxylic ester. One tri me-thylsilyl group migrates to the nitrogen atom, yield-ing the corresponding pyrazole (73%f37.3-Pyrazolyltrimethylsilane (48; R -R ' = H)m:Trimethylsilylacetylenc (4.91 g, 50 mmol) and diazomcthane (70mmol) in dry ether (100 ml) are kept in the dark !,)r 3 days at rl)onltemperature. After thc destruction 01' cxcess diazomethane by shortboiling. filtration and rcmoval 01' thc solvent in vacuum a1'fords thcproduct: yicld: 7 g (lOO'){,); I1l.p. 79-RO' (pentane); b.p. 113 114/14torr

Nitrile oxides 50 react regiospecifically with trime-thylsilylalkynes 39 to atTord the isoxazoles 51 21K

R2 R'R'-C: : :N70 + RLC: : :C-S i (CH3h - - -?> )j(H3ChSi o,..N

50 39 51R1 R2 Yield[%]

a HJC (H1ChSi 46b C,H, (H3 ChS i 44C ' ,3 ,5-tri-H3C- CSH2 (H 3ChSi 98d H3 C H 69e CsHs H 62

' ,3 ,5-tri- H3C- CSH2 H 98

The triazolyltrimethylsilanes 53-55 are obtained ingood yields via the addition of azides 52 to tri me-thylsilylalkynes 39239 e $RLN- N: : :N + R2-C:: :C-Si(CH3l3 - - - -752 39

R2)= (S i (CH 3l3 (H3C )3 Si ) = (R 2 R2WSi (CH3h.... N .... , + ....N .... R' +N R 'N ...I,R

53 54 55R1 R2 Yield (53) Yield (54) Yield (55)[%] [%] [%]

a (H 3ChSi (H3 CbS i 66b (H3 C)3 Si CsHs 87C CsHs (H3 ChS i 76d CsH s CsH s 3 97e CsHs COOCH3 80

CsH s COOC 2Hs 65

Preparation 01' Aryl- and Heteroaryltrimethylsilanes 855Triazoles of type 54 are also formed in low yields bythe addition 01' trimethylsilyldiazomethane to car-bodiimides 240

4. Introduction of Substituents into thc Nucleus ofAryl- and Heteroaryltrimethylsilanes

The often rigorous reaction conditions needed lorthe direct introduction 01' trimethylsilyl groups intoaromatic and heteroaromatic compounds (c.f. Sec-!.ion 2) require that various functional groups be in-troduced into the nucleus after silylation or subse-lJuently constructed by transformation of substi-tuents already present. Ideally, the trimethylsilylgroup plays thereby the role of an inert substituent.With the introduction of electrophiles, the desilyla-tion reactions' can dominate over the desired depro-tonation reactions, thus affording completely desily-latcd products. Desilylation is avoided by the use oforganometaUic derivatives which are always morereactive towards electrophiles than the correspond-ing hydrogen compounds. In the case of the transfor-mation 01' substituents attached to the nucleus, reac-tion conditions have to be chosen to avoid cleavageof the trimethylsilyl groups.4.1. H alogclla tiollHalodesilylation reactions proceed extremely weIl;thus the ipso-rate factor is lO x for the brominationand 10 for the chlorination 01' phenyltrimethylsi-lane'. Consequently, nuclear halogenation reactionswithout considerable halodesilylation are ooly possi-ble at strongly activated positions, for example in thep- and o-positions of m-trimethylsilyl-substitutedanilines and phenols 56.

HBr

56a-c

x Yield (57)[%]a OH 83b NHCOCH, '00C N(CH3)2 86

AS i(CH 3l3Sr

57 a-c

Br2HBr

Referenee

241, 242243, 244245, 246

X.,*Si(CH3b

Sr58a, c

The partial halodesilylation 01' bis[trimethylsi-lyl]benzenes 59 to the corresponding halophenyltri-methylsilanes 60 is of broader applicability (Table16).


16/36

856 Dieter Hbich. Franz Elfenberger

R , ~ H 3 h (H3C)3SiX/X2 >RVR 4R359 60

Table 16. Halophcnyltrimethylsilanes 60 via lIalodcsilylati(\n 01'Bis[trimethylsilylJbenlcne Derivatives 59Suhstrate 59 Yicld Refcr-R' R' R' R4 X [""J e n c ~ (H,q,si 11 11 11 J 40 95 42.247"11 (H,C) ,Si H H J X5 96 247"H H ( ~ " C h S i H 82 97 247'(H,C),Si H 11 H Br [42(H,C),Si (Clhh H Br 227(H,C),Si H (CII,).' Br 226(H,C),si H (CH ClI), Br Xl) 22X" Also used were J 2 .!Cl, an d JBr.3-Iodophenyltrimethylsilane 247 :At ()" a solution (11' idine hromide ([ 1.4 g, 0.055 mol) in carhon te-trachloride (30 rnl) is added dropwise to a solution of 1.3-bisltrime-thylsilylJhenzene (t 1.1 g, 0.05 mol) in carbon tetrachloride (HO ml),the mixture is kept fi.lr I to 2 h without cooling. Bromotril1lcthylsi-lane and carbon tetrachloride are distilled on ; tbe residuc is dis-solved in ether, washcd with 0.3 molar sodium thioslilfate solution(50 rnl). then witb water, and dried with sodilll1l sulfate. Dislla-tion affl)rds the prr


17/36

November 1979nyl chlorides 68 or by sulfonylation of unsilylatedaromatic compounds 67d, e with trimethylsilyl-sub-stituted sulfonyl chlorides 68 [R3 = Si(CH1 hF54 Trimethylsilyl-substituted thiophenols ( ~ 5 0 % ) areformed when the corresponding Grignard or li-thium compounds are allowed to react with elemen-tal sulfur255 ,256 or with diallyl sulfide H5 4.3. Introduction of Nitrogen FunctionsA number of arenediazonium salts 70 react with de-rivatives of aniline and phenol 71 (R4= NR 2 OH)carrying trimethylsilyl groups in the meta-position,to afford the azo compounds 72 (Table 17).

70 71R'R-QN:N-p-R4R3 Si(CH 3b

72Table 17. Trimethylsilyl-Substituted Azo Compounds 72 via Cou-pling of Diazonium Salts 70 with Aryltrimethylsilanes

71R'

HCICICF,SO,CH,SO,CH,HHNO,CICINO,CF,SO,CH,SO,UI,Ol lHHCOOHH11

R'

NO,NO ,NO,NO,NO,SO,CH,HNO,NO,NO,NO,NO ,NO,NO,S02CH,NO,SO,HS02NH,HCOOBSO,B

R' R4

HHCIHHBHHHHCICIHHHJlHHH11If

N(CH2CH 20H)2N(CB,CH,OH)2N(ClhCH,OHhN(CH2CH20H),N(CH,CH20HhN(CH,CH,OH),N(CH,j,N(CH,hN(CH,hN(CH,j,N(CH,hN(CH,),N(CH,hN(CH,),N(CH,hN(CH,hN(CH,hN(CH,j,N(CH,),N(CH,hOB

Yield Refer-[%1 ence50 16060 16060 16050 16052 16034 16060 143,24595 143, 24536 14377 14366 14335 143R3 14369 14351 14314 143X7 14375 14353 14365 143"257

------------------- - - - ~ - - - - - - - - - - - -a Includes azo derivatives of 2-naphthol.As expected, p-trimethylsilyl-substituted anilines orphenols undergo diazodesilylation 143. In contrast, 2-dimethylaminophenyltrimethylsilane does not reactwith diazonium salts due to steric hindrance 143.However, 2-trimethylsilylphenol couples in the 4-po-sition 258 . 2- or 4-trimethylsilyl-substituted azo com-

Preparation of Aryl- and Heteroaryltrimethylsilanes 857pounds can be obtained without desilylation occur-ring if the trimethylsilyl group is located on the di-azonium component 70 259 . A nitrosation of aryltri-methylsilanes while maintaining the carbon-siliconbond intact is also possible, but only with stronglyactiva ted anilines 245 or phenols257 of type 56.

56 a x = OHC X = NICH 3 )2

1. NaN022. HzO/H$ )

xYSi(CH3bNO73 a, C

The nitroso group has to be introduced by nitroso-destannylation reactions into less activated aryltri-methylsilanes, for example, to produce 3- or 4-ni-trosophenyltrimethylsilane (50%)260. Selective ni-trosodesilylation reactions were carried out with 3,4-bis[trimethylsilyl)pyrazole (74) leading to 75 (39-nW,) or 76 (36%)261.

(H3C13Si Si(CH3)3HN~ N ) H74 j-CsHgONO

76Sulfuric acid/nitric acid mixtures cannot be used forthe nitration of aryltrimethylsilanes because of theease of protodesilylation. In weakly acidic medium,phenyltrimethylsilane reacts with nitrating agentssuch as nitric acid/acetic anhydride, cop per nitrate/acetic anhydride, or others 102.262 265 predominantlymaintaining the carbon-silicon bond intact to form amixture of 0-, m-, and p-nitrophenyltrimethylsilanes.The somewhat favoured formation of the m-productis a basis for conclusions about the directive effect ofthe trimethylsilyl group26(,. For the specific prepara-tion of certain isomers it is more convenient to applypartial nitrodesilylation of the corresponding bis[tri-methylsilyl)benzenes 64 using nitric acid in aceticanhydride [0 (90%)142, m (69?1l)X5,265, p (82%f67J. Incontrast to earlier presumptions 6 ,2X these reactionsdo not seem to be explosiveM.2-Nitrophenyltrimethylsilane 42:A solution 01" nitric acid (70%; 6.3 g, 0.07 mol) in acel ic an hydride(30 g) is added slowly 10 a solution of l,2-bis[trimcthylsilyl]bcnzene(4.5 g, 0.02 mol) in acetic acid. The mixture is kepl at 100' for 6 h,then cooled, and added 10 0.4 molar aqueous sodium hydroxide so-lution (400 ml)_ Ether extraction, followed by washing, drying withsodium sulfate, and fractionation gives the product; yield: 3.5 g(90%); b.p_ 98 ' /2 3 torr; n;;: L5271.


18/36


19/36

November t979 Preparation of Aryl- and Heteroaryltrimethylsilanes 859ing butyllithium via the anion 86 to yield 87 (93%)with c1eavage of sulfur dioxide m,.nH3C)3Si S SOz-N(CH3}z

85

86N(CH3)ZJ j(H3ChSi S

874.4. Introducdon 01 Pbospborus Jtunction. .In order to introduce phosphorus substituents intoaryltrimethylsilanes, it is necessary to use organometal-lic compounds, because otherwise phosphodesilyl-ation27S occurs under the conditions of electrophilicphosphorylation (Table 18).

4.5. Alkylation and HydroxyalkylationSince aryltrimethylsilanes undergo alkyldesilyla-tion3279 under Friedel-Crafts conditions only, thepartial alkyldesilylation of poly[trimethylsilyl]ben-zenes can lead to the desired compounds. In thismanner the reaction of t,2-bis[trimethylsilyl]benzene(64a) with I-butyl chloride/aluminum trichloridegives 2-t-butylphenyltrimethylsilane142. Again, al-kyldesilylation can be avoided by the use of the cor-responding organometallic compounds 88. By reac-tion with alkylating agents R X, an access to var-ious alkylated compounds 89 is provided (Tablet9).

n( H 3 C h S i ~ y J - . . M R-X88

The biologically active thiophene derivative 90 is ob-tained by alkylation of the 2-lithio-5-trimethylsilyl-thiophene with oxirane and subsequent phosphoryla-tion (51%)179.'fable 18. Phosphorus-Substituted Aryl- and Heteroaryltrimethylsilanes via Trimethylsilyl-Substituted Or-ganometallic CompoundsSubstrate Phosphorylating Agent Pruduct Yield [%1 Reterence

.. *.- .. _._ .._*._._ .....*--~ H 1 C h S i - { ) 1 35 276

pels ~ H i C ) j S i { ) - l P 45 2'76~ H l C h S i - C } l /'.'0 30 2713

50 277

60 277

58 218

58 278

56 1'19

46 179

66 179

31 179_ ..._--_ .. . -----_ .._ - - -


20/36

S60 Dietl:r Hbich, Franz EtTenbergerTable 19. Alkylation of Aryl- and /Ictcroaryltrimctbvlsilane, via

Organomdallic Derivatives 88Substrate SSY M

-CH=CH- Mg8r-CH=CH- MgBr

-CH=CH- Li5 Li5 Li

5 Li

1.,&

R X

Cl);.., NN ' )-ClclNF1C=CF-F

O : ~ H 0D

90

Yidd[%]

15

32

50

29

Rl'Icr-ene.:

280281

282283175

2/.8

Alkyne-substituted aryltrimethylsilanes 93 can beprepared by coupling reactions of 91 with acetylenes92 2X4, as weH as by addition of trimethylsilylalkynes39 to benzyne 11,1,

91 92Cu/pyridine -0" 1---7) (H3CbSi _ \ C:C-R

SYNTHESIS

Alkylation of he ~ e r o a r y l t r i m e t h y l s i l a n e s containingnitrogen-hydrogen bonds leads to the N-alkylatedderivatives214 an d from compounds 94, salts 95 areobtained IX2.IX4.

94) ():>-Si(CH3h

IGl xeCH395a Y : 5, x" 0502F 187%)95 b Y : NCH 3 , X : J 191 %)

2-Pyridyltrimeth)lsilane was also eonverted into theeorresponding quaternary iodide (':11 ~ \ , ) ~ I , The free radieal arylation of phenyltrimethylsilaneinduced by dibenlOyl peroxide gives a mixture oftheisomerie trimethylsilyldiphenyls (overall yield2()'J6f x5 , Hydrox:ralkylation of aryltrimethylsilaneswith aldehydes in the presence of aluminum triehlo-ride always l e a d ~ ; to mixtures of isomers286 , Orga-nometallic derivatives 96, however, reaet with alde-hydes and ketones speeifically to give the corre--sponding alcohol 97 (Table 20),

96

)

97Tahle 20. Benzyl AIcJhois 97 via Rcactions PI' Grignard C011l-

pounds 96 with Aldehydes or KetonesYicld Rcfcrcncc[%]91 9J93 a R1 : -C-O-CH-OC,H". 185'10) CH ,I H 33 50 65, 169. 2XI, 2g7, 2 ~ 8 CH 2 --CI eH, eil, 42 49 2 ~ 1 , 2XX, 289, 290

FOBr [0]93 b R2 : N(C 1Hsh i21 '/0)93 C R2 : NICH 3 l1C sH5) 116'10)

Pentafluorophcnyltrirm:thylsilane can be alkylatcdwith n-butyllithium in the 4-position as the result ofdirect nucleophilic attack 1 9 ~ .

C"II, " 20 52 65,212

Analogous reaeti Jns 01' 2-lithio-5-trimethylsilylthio-phene with benz.lldehyde (yield: 30W,f91 as weIl aso[ the 5,8-dilithin adduet of 1-naphthyltrimethylsi-lane with aliphatie aldehydes CH3(CH2)nCHO(n=O, 1, 2. 3; yields: 3 7 ~ 4 6 % f i 9 have: been de-scribed.4.6. AcylationNormal acylatioll competes with acyldesilylation intbe Friedel-Crafls aeylation of aryltrimethylsilanes,Thus, acyldesilylation of phenyltrimethylsilane (98)


21/36

November 1979with acetyl chloride/aluminum trichloride is greatlyfavoured over the normal C- H acylation by anipso- rate factor3.279 of 10'-104.With acyl fluorides/boron trifluoride, however, bothreaction pathways seem to take place at a eompara-ble rate yielding a mixture of 99 andtOO('-' " ) ~

98

o11 /R-C-F/BF 3 )

o111 +a C- R

99

{ jrSi(CH 3l3:/1R-C11o

100a R = CH 3b R = C6H5

Normal acylation is favoured when strong substi-tuent effects counteract the ipso-directive elreet ofthe trimethylsilyl group. Thus, 2- and 3-methoxy-phenyltrimethylsilane are always acylated para tothe methoxy group5 I,2Sg, 163 and do not undergo acyl-desilylation as was earlier reported 279 The relationswith 3-thienyltrimethylsilane (101) are similar. Com-pound 101 exclusively reacts at the position that 1'a-vours an electrophilic attack to yield .02 (R = CH"Cc,H 5; using tin (IV) chloride titanium(IV) chloride,aluminum chloride as catalysts; yield: 14-52%?1.The mineral acid emerging 1'rom normal acylation,in the presence 01' the catalyst causes protodesilyl-ation 01' still unreacted 101 1'orming thiophene,which is subsequently acylated to yield 103 (24-59'1(,). This side reaction has not been seriously lakeninto account in most of the earlier investigations./j"\('S (CH313t,; o11 /R-C-Cl catalyst )101

+ n-C.....((s)l11o102 103

The acylations of 2-thienyltrimethylsilane [acetylchloride/titanium(IV) chloride (42%)'1, acetic anhy-dride/iodine (13%)293, benzoyl chloride (17%)2'14],2_furyltrimethylsilane [acetic anhydride/iodine(25W29J], and N-methyl-2-pyrrolyltrimethylsilane[phthalic anhydride (55%)294] lead to the 5-acyl-2-tri-methylsilyl compounds. The only moderate yieldsindicate that side reactions, involving acid 1'ormed byacylation, also take place in these cases. The partialdesilylation of poly[trimethylsilyl]aromatic com-pounds provides a convenient way to prepare acyl-phenyltrimethylsilanes. Since the reactivity 01' the

I'reparation 01' Aryl- and Heteroaryltrimethylsilanes R61mono-acylated compounds is significantly reducedno further reaction takes place 142.2-Acetylphenyltrimethylsilane' 42;Acetyl chloride (2,3 g. 0.03 mol) in carbon disulfidc (15 1111) is ad-ded to a stirrcd. i cc-wolcd suspension 01' aluminum chloride (4.0 g)in carbon disultidc (:i0 ml) containing 1,2-bisltrimcthylsily1Ihcn-zene (6.ti g, (J,(J3 mol). Thc mixture is heated under rcllux I(lr I h.most of the solvent is distillcd oll, and the residue is addcd to ice/water (!OO 1111). Bcnzene extraction f(lllowcd by washing. dryingwith sodium ,ulfatc, and fractionation givcs the pmduct: yicld: 2.8g (50%); b.p. 88/3 torr; ni; 1.5181.The unwanted side-reaction, acyldesilylation, in thepreparation 01' acylaryl- and -heteroary ltrimethyl-silanes can be completely avoided by using the reac-tive organometallic derivatives 104. In this case, in ad-dition to the usual acylating agents (i.e. acyl halides oranhydrides), which direct1y affords ketones 106 (routea), nitriles also can be used. Primarily, the imino deri-vatives 105 are formed (route b), which after. hydroly-sis give the ketones 106 (Table 21).

0 011R-C-X fI(H3CbSi-Ar-C-Ra 106

(H3C13Si-Ar-M i 2olH'1l104 b NHR-C::::N fI(H3CbSi -Ar-C-R

105To obtaill acylphenyltrimethylsilanes 109, the tri me-thylsilyl group can also be introduced by the acylat-ing agentt07, generally involving Friedel-Crafts ca-talysts (Table 22).

107 a orthob metaC para

108

109Trimethylsilyl-substituted alkyl aryl ketones are ob-tained by addition 01' aliphatic Grignard compoundsRMgX (R = CH), C2Hs, C6H I " Cr,H"CH2) to 4-cy-anophenyltrimethylsilane296 The formylation of aromatic compounds is a specialacylation reaction. Reactive aryltrimethylsilanes un-dergo direct 1'ormylation according to Reimer-Tie-manu 257 ,270,2


22/36

862 Dieter Hbich, Franz EtTenberger SYNTHEsrsTable 21. At:ylaryl- and Acylhctcroaryltrimcthylsilanes 106 via At,,.ylation of Organornetallic Cornpounds104- - - - - - -_ ._*" - . - _ . _ - _ . _ . - . ~ . _ . _ . - - - - -._. _., - - ......__ ._ ....- .' ..._._ .... _._... ..._-----_ ..._- - - - -Sub!ltrate 104 Routc Acylating agent Proouct type Yieldl%1 Rcterences-_.,.__ _. ----. _ - ~ _ . - ~ . __ . _ . ~ - .* _-- _- _ . . ~ ~ __ _ _ " ~ ~ _ H _ . _ .___ ...__ . _ * ~ . ___ __ . ~ . IH: .ChSb-

'_ ' MgElr b H:iC'{)-CN 106 82 16A( H ~ C ) 3 S i - { ) - M 9 B r b H3C-{}-CN 106 64 166(HlC};Si -o" MgBr b H3CO-{)-CN 106 33 168( H 3 C } ' S i ~ L i '- b Cl O-CN 105 75 248

Cl(H,C)3Sit r Li b C}CN 105 51 248( H 3 C l 3 S i ~ L i \ I. b H ,COCN 105 54 248iH,C) ,S i t r Li b t J -CN 105 30 248(H:iCh Si_i.jrLi b N ~ c t ~ 10 5 SB 248

0 0IHJCl,Si-{}MgBr " ~ I I I I - f ~ : c-o-c I:::,> 106 (R: f} ) 33 295

0 0IH lChSi-f:}M9B r 11 11 106 IR : H3C)H C-C-O-'C-CH 3 39 29:

0 (>!H,Cl,Si-{j-Mger 11 11 106 IR ClHS)C2H5 ""C-'O-C-C?H; 44 295

0 0IH iC)3 Si - ( }MgS r 11 11 106 IR = n-ClH,)n-CJH7""C" 0""C-,C311 1-1 ) 31 295tH3ChSi 0H 3 C O ~ C d C ! 11 106 IR H,ClHJC- C-,Cl 41 20'/- - - - - - - - - - - ~ - - - - - - - - _ .. ,- . _ . _ - - ~ - - - - - - _ .._._-_. -_._-_ .._-- - - - - - - -'fable 22. Bcnzoylaryltrirncthylsilanest09 via Benzoylation withTrirnethylsilyl-Substitutcd Benzoyl Chlorides i07", , - - - - - - ~ --._-_.__._----_._._------- ._ ...__ -Rea


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Novembcr 1979 Preparation of Aryl- and HetcroaryltrimethyL'Iilanes 863Table 23. Trimethylsilyl-Substituted Aromatic and Heteroaromatic Carboxylic Acids 110 via Carboxylation or Organomctallic Cllm(lounds104Substrate Yield Refcrcnce Substrate Yield Reference104 ( ~ V , J 104 (%1. - ~ - " ' - - - ' - ' * ~ - - - ' " ..._.__ ...-.......)ilCH 3h ( H ' C I ' ~ ( \ Li 60 142, 168 F I' '\ Li 171!HlCllSb- CI F 1'_'\ -Li 48 85, 9 ~ 1 , 144 IH,CI,Si-'Li 62 293(H)CljSi-Q-Li 38 - 66 99, l8, 300(HlCl.lSi ( H , C I , S i ~ L i 62" 293HCO{)-U 207{ H 3 C ) l S i - { J - { ~ } U I H , C I , S i ~ L i 48 30140 lS? CI CI( H 3 C ) l S i ~

"-5-::.\ Li 171 IH,CI,Sifr.SOz-NlCH3Iz 10 176F F H Li-_._-_ ._--_._----.- .__ . .. "-"---"'-' -. . ----_._.- . _ .. . .._--_ .._- . Treatment with cthyl chloroformate anords the corresponding lumn carboxylic estcr (59%):'2.

'l'able 24. Silylation or Organometallic Derivatives or Aryl- and H e t e r o a r y 1 t r i m e t h y l ~ i l a n e s - . _ - - - - - ~ - - - - ~ . _ - _ . _ - - - - _ .... _.--------_.__ ._----- -._._ ._._---_ . _ .._-- .... ,-_._---_.Organomctallic Derivative Silylating Agent Pnlduct Yield ( \ ~ ' J Rdcrencc-_ . _ - - - - - - - _ . ~ - - _ . _ - - _ . ~ - _ . _ - - - - - - - ~ ...- . . - ._._._---_. .._. ---_._. .... _. _--- ---CH! CH]

IH,ChSi_Q_M9CI C I _ Q _ ~ i - C l I H 1 C h S i _ Q _ ~ i _ Q _ C I 52 303"- ICH, CH,CH3

IH,ChSi_Q_ M9Br H3C-SilOC2HSh I H 3 C I 3 S i _ Q _ ~ i - O C 1 H 5 57 252- IOCzHsIH3ChSi_Q_U

CsHsICsHshSiCI2 I H 3 C I 3 S i - Q - ~ i _ Q _ S i l C H , I , 86 140- I -C6HS

IH'CJ,Si_Q_U SiCI, ~ H 3 C l , S i _ Q _ l Si 77 140CH3

IH,Cl,Si_Q_Li IH,Cl2SiCI2 I H 3 C I 3 S i _ Q _ ~ i _ Q _ S i I C H , I , 41 167- I -CH,CI CI CH, CH,

IH,ChSI_Q_U I I IH3CI,Si_Q_Ji-O-Ji_Q_SiICH,I3H,CI2S/-Q-SIICH,12 20 167- I I-cH, CH,I H , c h S i ~ L i

'fHs i H3CeHs-Si-CI I H 3 C h S i - o - ~ i - C 6 H s 30 291A ICH, CH,i H3 erH,I H , C I , S i 1 ) - - ~ i - C H 2 L i IH,C),SiCI ( H 3 C I , S i ~ S i - C H 2 - S i I C H , 1 , 17 291ICH, CH,rH3 iH, rH, TH,I H , C h S i ~ ~ i - C H 2 l i C s H s - ~ I - C ( ( H l C h S i ~ S I - C H c S i - C 6 H s 17 291A I ICH, CH, CH, CH,

1H3C1,So.- IH3ClsSi1'_'\ CI Na/F-SilCsHsh O-SilCeHsh 75 252

" Fuether trimetbylsilyl-substituted oligomen; are liMcd bere.


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864 Dieler Hbich, Franz EtTenbergcr4.8. SilylationThe stability 01' carbon-silicon bonds towards orga-nometallic compounds makes it possible to introducefurther silyl groups into aryl- and heteroaryltrime-thylsilanes. The hereby applied methods are not dif-ferent from those used to introduce the first trime-thylsilyl group (d'. Section 2.3.) (Table 24).4.9. ProtonationProtonation of aryl- and heteroaryltrimethylsilanesleads to the formation of salts, protodesilylation. orreplacement of other substituents by hydrogen, ac-cording to the substrate and the reaction COlH.li-tions.Basic heteroaryltrimethylsilanes 11f or 94 react withacids to form salts 112 01' 113.

.. H-X )R N Si(CH3h111

R = H; X = Cl, Hr. .L BF/'R = 11, Br, Si(CH ,h : X (icCh " ,

94Y =S: X=Cl. 1"4Y=NCIl,: X=Cl""y = S: X = (JeU 3 1114

112

~ Y } - S i ( C H 3 l 3 ~ N $ Xe

113

3,4-Bis[trimethylsilyl]pyrazole (114; R ,= H) can beconverted quantitatively into its nitrate or hydro-chloride by treatment with concentrated acids 105 .However, in sulfuric acid/ice, protodesilylation oc-CUfS. Thus, the trimethylsilyl group of 114 (R oe= H,COOC2 Hs) can selectively be removed from position3- or 4-, according to the reaction conditions215 .

Si(CH 313RJ[)IH115 (100%)

114

4.5-Bis[trimethylsilyl]-3-methylisoxazole behavesanalogouslym. 3,5-Bis[trimethylsilyl]-I-methylimid-

azole is smoothly hydrolyzed in a water/dichloro-methane mixture to give 1-methyl-5-(trimethylsilyl)-imidazole (90%) 1:';. Halide substituents in aryltrime-thylsilanes H7 caH he replaced hy hydrogen via theorganometallic intermediate without reaction occur-ring at the trimethylsilyl group 171.

:*":"117

1. n-C4HgLi2. H20

SHCH3bFrJ-pFXYHF118a x = F (75%)b X = CI (75 %)

5. Transformation of Substituents in Aryl- alldH c t e r o a r y l t r i m ' ~ t h y l s i l a n e s

Aside from the substitution reactions at the nucleus01' aryl- and heleraryltrimethylsilanes, the transfor-mation and functionalization of substituents, at-tached to the silylated ring, is an important methodfor the preparation of some aryltrimethylsilanes.Hereby, it is impOl ta nt to choosc reaction conditionsthat do not permit desilylation reactions.5.1. NucleophiIic Ex


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N o \ ~ m b c r 1979 Preparation of Aryl- and Heteroaryltrimethylsilanes 865(X = CN) in yields of SO_90%106.307, afford the me-thyl esters when treated with diazomethaneJ(j(,. Thecorresponding amide is obtained in 83"h yield 163from the reaction of N,N-diethyl[2-trimethylsilyl-phenylethynyl]amine with hydrogen chloride/ether.The acidic n-C H bond of 4-cyanomethylphenyl-trimethylsilane 119c (X = CN) can be methylatedwith sodium amide/methyl iodide (80W,) or acylatedwith sodium ethoxide/ethyl acetate:l07. Salts ofC H acidic compounds 120 have been used as C-nudeophiles to afford compounds 121.lox .

62c

HIeC-R 1

120

H--7 ( H 3 C b S i ~ C H z - t - R 1 "=T IRZ121 a R' : R' : COOC ,H, (22%)b R' : COCH3, R' : COOC,H5 (17 %)

The conversion of the benzyl bromide 62c to theGrignard derivative 119c (X = MgBr) and subse-quent treatment with sulfuryl chloride leads to thesulfonyl chloride 119c (X = S02Cl)109.Substitution reactions on 4-[-chloroethyl]-3fl7 asweU as 4-[3,5-dichlorotriazinyl]phenyltrimethylsi-lane2xo with amines have also been described.As expected the dibromomethylbenzenes 63 can behydrolyzed to give the benzaldehydes 122 (49-69'),;) 101,1 (,9. 249. 2:;O.} 10.

(H3C13Si-o-CN126

5.2. Functionalization of Carboxylic Acid DerivativesTrimethylsilyl-substituted benzoic acids 123. easilyobtainable by carboxylation reactions (cf. Section4.7.), afford the acyl chlorides 124 when treated withthionyl chloride 16X,172. 30X, 311. The conversion of acylehlorides 124 to the corresponding acyl amides 125can be effected easily with ammonia or am-line62. 144, 16X,.10X.

Si(CH 3bG-COOH

123 a orthob metaC para

124 a-c

125a-c R : H, C6H5Acyl chlorides, obtained in a similar maIlller from 3-and 4-trimethylsilylphthalic acid, form esters onreaction with methanop12 and with ammonia giveaeyl amides]04,312.The methyl esters of 4-trimethylsilylbenzoic acid x'.4-trimethylsilylphenylacetie acid 06 , and 4,4' -trime-thylsilyldiphenylcarboxylie acid 1 ;7 can be prepareddirectly from the acids by using diazomethane. An-other pathway to aequire derivatives of 4-trimethyl-silylbenzoic acids starts [rom 4-cyanophenyltrime-thylsilane (26), whieh aceording to the reactionconditions, can be converted to the amide 127 or theiminoester hydrochloride 128. This permits the pre-paration of the ester 129 or the amidine 1302


26/36


27/36

November 1979 Preparation 01' Aryl- and lIeteroaryltrimethylsilanes R67

KCN o OH(H3ChSi -Q-g - tH-Q-Si (CH3h

o{H3 Ch Si-Q-g-H

122c

methylsilyl-substituted phthalocyanin, indigoide,and triphenylmethane dyes have been prepared bycondensation reactions using the appropriate trime-thylsilyl carbonyl compounds204.297.314.R1

148H

In(H3C)3Si "-"'S,,/\ JR S150a R = H (70%)b R = eH3 (51%)

149 a Y = 5 (92 %)b Y = 0 (92 '10)

Alcohols of the type 151 in the presence of variouscatalysts (aluminum oxide 300-340", 39_52%2x7.m;potassium hydrogen sulfate, 240 0 , 43%65; phospho-rus pentoxide320 ) can be converted into styrenes 152by thermal gas phase condensations.

151

catalyst, \J )- HzO

152 a R = Hb R = CH 3Elimination of water occurs when trimethylsilyl-phthalic acid or trimethylsilylphenylthienylcarbinolsare heated to yield the corresponding anhydride(100% )204 or ethers (30%)2


28/36

E{6E{ Dieter Hbich, Franz EffenbergerTablc 25. Oxidation Rca


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November 1979silylaryl derivatives of carboxylic acids and serinecan be reduced to yield the corresponding alcohols(up to 90%)307. Corresponding nitriles are reduced toprimary amines29b ,307. N-Substituted amines of thetype 169 are obtained by reduction of acyl amides 163or by reductive cIeavage of 168 using lithium alumi-num hydride324

LiAlH 479- 84 Of,)

Reduction of trimethylsilyl-substituted phosphineoxides by lithium aluminum hydride gives thephosphines277 .Other procedures for the convenient preparation ofbenzyl alcohols from benzaldehydes are, 1'01' exam-pIe, the treatment with tin(ll) chloride/hydrogenchloride296 , normal or crossed (formaldehyde/OH ')Cannizzaro reactions2%,325 and the reduction by tri-alkylsilanes in the presence of zinc chlorideJ2{,.Reduction processes are the most important methodsfor the preparation of aromatic amines. This also ap-plies to the trimethylsilyl derivatives. Thus. azo com-pounds 170, nitroso- 171, or nitroaromatic com-pounds 172 can be converted into the amines 173 ifthe appropriate reducing agcnts are applied (Table2(-' ).

R')PRVR 4R3170 a x =N=N-C6Hs171 x = NO172 x = N01

173

Preparation 01' Aryl- aud Heteroaryltrimethylsilanes5.7. Metal Complexes 01' Aryl- and Heteroaryltrimethylsi-lanesBy the complexation 01' the 1T-system of aryl- or ofthe nitrogen atom of heteroaryltrimethylsilanes. thereactivity of the carbon-silicon bond can be drasti-cally altered.Metallation of (ll-benzene )-( 17-pentafluorobenzc-ne)chromium with n-butyllithium and bis [benze-ne)chromium with n-butyllithium/tetramethylethy-lenediamine and subsequent silylation atTords[(Cr.Hh )Cr[C6 Hs Si(CH;h)l ( n ~ ! ( ; ) m and[C6H., Si(CH 3hbCr (37%)32, respectively. Further-more. oxidation of the chromium atoms in thesecomplexes can also be used to cause a strong varia-tion in the reactivity of the carbon-silicon bond.12S.The chromium tricarbonyl complexes of phenyltri-methylsilane and the bis[trimethylsilyl)benzenes64a-c are fonned when these compounds are heatedtogether with hexacarbonylchromium 32 9,1\0.Trimcthylsilylhcnzcnc timc the hexa.:arbonyl-~ h r 1 l 1 1 1 i u 1 1 l wh ich sublimes i nto the ai r cllndenser is p c r i o d i ~ a l l ) pushed back iuto the rcaction tlask with a long spatula. A ydhlwwlour dcvclops slowly in the rcactilln mixture. and a small anwuntll f solid is frmeJ. Thc 11lixture is then cOliled and diluted with et-her (1001111). Filtration through a short column 01' dcactivatcd alu-mimt is flillowcJ hy removal 01' volatiles at redun:d prcssurc_ Thcycllow crystallinc rcsiJu c is recrystallized frOI11 aqucolls cthanlll tngive lhe prodU':l: yidJ: O.5tJ g (20'),,): m.p. 72 73. An analyticalsam pie was suhli11lcd at 60 -65 /O.tl1 torr.Ferroceny1trimethylsilanes 175 [R 1 = H.R = Si(CH,h: 50;?!;)"1 are prepared from cyc\open-tadienyltrimethylsilanes 174 using n-butyllithiumand iron(11) chloride. Metallation of ferrocenes 176(R 1 = H) with sodium 13 2 or n-butyllithium 33-u 1 4 andsubsequent silylation affords mixtures 01' 175(R 1 =R 2 =H; 19-23%) and 175 [ R 1 = H .R2= Si(CH I),; 27-50%); in the case of (dimethylami-

Taille 26. Trimet hylsilyl-Substitu tcd A11linohenzcncs 173 via Rcdllction 01' Am. Nitroso. ur Nitro CompounJs- ~ - " , - - . _ ~ . - - - - - - - - - - - - - - -

Type R' R2 R' R' RcJucing YiclJ Refcrelll'cAgent [",1_ . _ . _ - - - - , - - - - - ~ - - - - - - - - - ~ ~ - - - - . ~ - - - - - - -- - -- -- -- - -- _ . __ .170a Il (H,C),Si Ol l 11 Na2S,O, 25X1701l (H,C),Si H Ol l 11 Na,S,, 95 257171 (H,C),Si H 11 Ol l Pd/c' 11, 257171 (H,C),si 11 N(CII,), H Pd/Co 11.- 2-l5172 (H ,C),Si 11 H 11 Rancy-Ni/ll, X3 144172 11 (H,C),Si 11 11 Rancy-Ni/II, 85 71). 1-l4

I'J/c, 11., 243. 265172 H 11 (II ,C),Si 11 Rancy-NijH, 75 N.144Pd/Co 11 2 2-l3172 (II,ChSi fI CI 11 Raney-Ni/lh 75 271172 NHCOCI-I, 11 (lI,C),si 11 Pd/Co 11, 24.1172 (ILC),Si H (lI,Cj,N 11 Pd/C. 11, XI> 245172 CH , H 11 (11 ,C),Si Rancy-Ni/II, l)() 314


30/36

870 Diete) Hbich, Pranz Effenbergerno)-methylferroeene 176 [R ' =CH 1N(CH,hl "ortho-metallation" favours seleetive reaction to give 175[R ' =CH 2N(CH 1b R2 = H; 79%]13',2Q

H Si(CH3hn-SuLi/FeCt2

174

1. Na 0, n-C4HgLi2. (H3CbSiCl 175

176The methiodide of 175 [R 1 =C H2N(CH,h, R2 =, H]readily undergoes nudeophilic substitution of thetrimethylamino group by aqueous hydroxide (85%),phenoxide (85%), aniline (95%), and piperidine(66%)1.15. The reaction 01' the 'lT-cyc!opentadienyl-irondicarbonyl anion with pentafluorophenyltrime-thylsilane gives 177\3.

F F@-F e ( CO l ? - t t Si(CH3l3F F

177The paUadium(Il)J37 and gold(l)33H complexes 178and 180 of the silanes 94 and 179 are formed, when

94

Agent y

PdCI,(Cr,HsCN), SPdCI,(C"H,CNh NBAu(CO)el SC 7 ~ L N S GcCl, NCII,

M

'/, PdCh'/, PdCl,AuCI(,cel,

178Yield

91637360

Refer-

33733733X304

h , agenl/CH2Cl2 or C6H6 , r.l.~ . , ~ ~ - - ~ - - - - - - - 7 ) ~ . , ~ 'N Si(CH313 Si(CH3bM

179 180 a M = i PdCl, (84 '/0)b M = AuCl 192 '/0)

SYNTHFSrs

these compounds react with PdCI2(ChHsCNh, goldchloride or gold carbonyl chloride. Dichlorogerm-ylene complexes 178 are obtained in a similarway304. The carbon-silicon bond of aU complexesproves to be less reactive than that of the free sila-nes.5.8. MisccllancousIn c!osing, some types 01' reaetions and compoundsthat do not readily fit into one of above categoriesshould be mention ~ d . The phosphonic esters 181 reaet with phosphoruspentaehloride to yield the dichlorides 182 whieh eanbe converted into the phosphine oxides 183 usingGrignard agents or into the phosphonie acids, whenhydrolyzed 277. 3\9.

181 182

183Halogenation and .;aponification are simila.rly appli-eable to the trimethylsilylphenylmethanephosphona-tes277 Similar to tte tertiary amines 143 (cf. Seetion5.3.), the p h o s p h i n l ~ s and arsines 184 ean be eonver-ted into the corresponding quaternary iodides185277, 27X, 3:19.

184a-c 185 a M " P, R = CH 3 (40-50'10)b M " P, R = C2HS (58'10)C M " As, R = eH)

Dimethylarsino groups are introdueed into aromatierings like most of the phosphorus substituents (cf.Section 4.4.). The organometallic compounds 186mare involved as i n t , ~ r m e d i a t e s .

186

187 \60 '/0\


31/36

November 19794-T rimethylsilyl- t-arsabenzene (189) can be prepa-red in 83% yield by treating 188 with arsenic(lII)chloride340

188

189Sulfonyl chlorides 191 are prepared from salts ofsul-fonic acids 190 employing phosphorus pentachlori-dem, thus enabling the preparation of sulfonamides192252, }O'i.

pels---?

190 191

192Reactions involving halide exchange on tri fluoro-methylbenzenes 193,1,341 to give 194 and on ethoxy-silanes 195252 to yield 196 have been carried out.

193

195

6. Conclusions

HF---;.

196

194 aar /hob para

Although the number of publications concerningaryl- or heteroaryltrimethylsilanes is increasing mar-kedly, it does not seem very likely that dramaticallydifferent preparative methods from those describedhere can be expected for this class of compounds.

Preparation 01' Aryl- an d Heteroaryltrimethylsilanes 871In contrast, the better understanding of their rea\.'-tions and, therefore, of the scope of their prepara-tive utility is still in its infancy and, thus. the systemholds promise for interesting future developments si-milar to that of the chemistry of vinylsilanes and si-lyl enol ethers. It is hoped that this article has provi-ded so me stimulation tor achieving that develop-ment.

R e ~ e i v e d : Fchruary 12. 1979

* Author to whom c o r r c s p o n d c n ~ e should he addresscd,I E, W. Colvin. Chon. So('. Rev. 7. 15 (197R); a review with 250

r e f ~ . T. 11. Chan. I. Heming. Svnlhesis 1979, 761. a review with 170r e f ~ . K. Utimoto, T. Mllkaiyama. K. Saigo. Kagaku No Rroiki. Zo-kan 117, 114 40 (1977); C. A. 90. 6434 (1979).J. K. Rasmllsscn. SYllthesis 1977.91; a review with 125 n : f ~ .

I C. Eahofll. J. Orgallomel. Chem. tOO. 43 (1975).4 Y. Sakata, '1. Hashimoto (Shizuoka. ('oll. Pharm .Iap.) S I z i ~ I I

oka Yakka Daigaku Kaigaku. IO-ShllllCIl Kinen RomhlllHku1963,77; a review with 50 rcfercnccs: C. A. 60.1787 (19M).'. C. Eahofll. Orgallosilicof/ Cornpounds. Butterwllrths. L,'ndon.

1


32/36

872 Dieter Hbich, Franz EffenbergerM. lshikawa et al.. J. Orgallomet. Ch.!m. 152, 155 (197X).M. Ishikawa. T. Fuchikami. M. Kumada, J. Orgallofllet.Chem. 133, 1 R. (1. NcviHc, J. Olg. Chern. 24,111 (1959).I.; V. E. Nikitcnkov, Zh. Ohshch. Khiln 3.l641 (1463): C. A. 59,

653 (1963).( , ~ L. W. Hrecd. Vv. J. Haggcrty. Jr., F, Baiocchi, .I. Org. ehen1.25, 1633 (1960).().; K. Bowden. E. A. Braudc. J. ehen1. Soc. 1952. 106X.70 A. D. Petrov. T. I. , N. ~ ; . Nametkin, Chan-Li Gu, N. A. Lennova.

Dokl. Akad. Nauk SSSR 118, 731 (195X): c. A. 52. 11769(195X)./', N. S. Nametkin, A. V. Topdlicv. 1.1.l/ed. Oh!. Kremi/Orgall. So

edill, Silllez. i. Fiz. Kilim. Sl'oi.l'11'lI, Akali. Nauk SSSR, Illst.Neftekhim. Silllczll Sh. SIlllei 1962. IY(); C. A. 58, 6X52(1963).

I', V. Chva!ovsky, V. Bal,ant, Chem. !,isly 46, 15X (1952); C. A.47. R030 (1953).M. Bullpitt, W. Kitdling, W. Adcock. D. ))\)ddrell, .I. Orgallo,mel. Chef/!. IUt, 161 (1976).Y. Limouzin. 1. C Mairl', .I. OrWll1omel. Chef/!. 63, 51(1973).

7'7 J. M. Angellel i, J. C Maire, Y. Vignollet. J. Orgallomel. Chem.22,313 (1970).C. Eahorn. J Chem SOl'. 1956. 4X5X.

SI Y P. Egorov, C. A Leites. N.


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November 1979" A. D. Petrov, E. A. Chcrnyshev, Guan-Lian Li, f)okl. Akad.

Nauk SSSR 132,1099 (1960); C. A. 54.20995 (1960).X9 K. A. Andrianov, V. E. Nikitenkov, N. N. Sokolov, Izv. Akad.

Nauk SSSR. Otd. Khim. Nauk 1960. 1224; C. A. 55, 429(1961).X R. A. Benkeser, H. R. Krysiak, J. Am. Ch


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R74 Dieter lIbich, Franz EffcnbergerIh'.1 E. Cilydc, R. Taylor, J. ('Ilem. SOl'. PerJ..il1 Trans. 2 1973.1632.1/ 0 E. Reinlanll. L Langwielcr, Arch. Phartll. (JYeinheim. U:'r.)308, 888 (197:;); C. A. 84. 74334 (1976).I/ I K. Kuroda. N. Ishikawa. Nippon KaKaku Za.\shi 91. 4X'!

(1970): C. A. 73.66669 (llJ70).M. R. Smith. 11. Gilman. J. Or[!,llnOl1!ef. Cht'm. 42.1 (1972).171 G. M. Davics. P. S. Davlc,-;, Tetrollet/roll I.elf. 33, 3 ~ ; 0 7 (llJ72).i74 K. P. C. Vol1hardt. L. S. Yce, .I. Am. (,heIlI. SOl'. 99, 2010(1977).I " P. A. Konstantinov. R. I. Shllpik. Zh. Ohsh"h. Khim. 33. I :!51(1963); c. A. 59. tlll02 (1%3).1,'(, L>. W. Slocum, P. L. (i-icrer..I. Org. ehen1. 3ft 41X9 (1')73),

S. F. Thamcs. J. E. M


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Novcmber 197924' T. lIashimoto, Yakugaku Zasshi 80, 1399 (196(): C. A. 55,5393 (1961).24 ) A. I). Petrov, V. P. Lavrishchev, lzv. Akad. NauA. SSSR, Otd.

Khim. Nauk 1952, 1125: C. A. 48, 124!\ (1954).241 Y. Sakata, T. Hashimoto, Yakugaku Zasshi80, 72X (1960): C.

A. 54, 24480 (1960).244 A. D. Petrov, E. A. Chernyshev, 121'. A kad. Nauk SSSR. Old.

Khim. Nauk 1952, 1082; C. A. 48, 565 (1954).24 ' T. Hashimoto, M. Seki, Yakugaku Zasshi 81, 204 (1961): C. A.

55.14340 (1961).24'. A. D. Petrov, G. I. Nikishin, Im Akad. Nauk SSSR Ott!.

Khim. Nauk1952, 1128; C. A. 48, 1247 (1954).247 O. F elix, 1. Dunogues, F. Pisciotti, R. Calas. A n g ~ w . Chl'lI1. 89,502 (1977); Angew. Chell1. Inl. Ed. Eng!. 16,488 (1977).24> F. 11. Pinkerton, S. F. Tahmes, J. /Il'terocyc/. (,hell1. 9, 715(1972).24:, Y. Sakata, T. lIashimoto, Yakugaku Zasshi 79, K72 (1959): (',

A. 54, 357 (1960).2.,


36/36

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Printed Org a No Silicon Compounds Eff119

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