Final Report Amit Nayak

7/30/2019 Final Report Amit Nayak

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Amit Nayak B.Tech Pharma Project report Green Synthesis of Vorinosta

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The Green Synthesis and development of anti-cancer drug

Vorinostat by using a solid heterogenous catalyst Sulphated

Tungstate

A PROJECT REPORT

SUBMITTED TO THE UNIVERSITY OF MUMBAI IN PARTIAL

FULLFILLMENT OF THE DEGREE OF

BACHELOR OF TECHNOLOGY

IN

PHARMACEUTICAL CHEMISTRY AND TECHNOLOGY

BY

Amit P. Nayak

UNDER THE GUIDANCE OF

Dr. K. G. Akamanchi

INSTITUTE OF CHEMICAL TECHNOLOGY

DEEMED UNIVERSITY

UNDER SECTION 3 OF UGC ACT 1956

MATUNGA (E), MUMBAI 400019INDIA

APRIL 2011


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Acknowledgements

I take this opportunity to express my deep sense of gratitude and reverence to Dr.K.G. Akamanchi, Dept.

of Pharmaceutical Sciences and Technology, I.C.T. for his keen interest, inspiring guidance, and

invaluable suggestions towards this project. I am thankful to him for his support. The training and

experiences I have got here will be of a lot of importance in my career ahead.

I am thankful to all the faculty members, all non teaching staff members and my entire B.Tech class for

their co-operation and moral support. I want to take this chance to thank our head of the department; Prof.

Devrajan for making available all the facilities required to complete the B.tech Project.

In the nutshell I would like to thank everyone who contributed to this project, without their support this

work would not have been successful. I would like to give my sincerest gratitude to KGA lab workers

Pramod, Rahul, Ravi, Abhay, Ashish, Arun and Prof. Chaturbhuj for guiding and assisting me during the

course of this project.


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Preface

The project describes the use a novel catalyst sulphated tungstate to carry out an amidation

reactions leading to the synthesis of an anti-cancer drug Vorinostat. A series of reactions havebeen taken with varying parameters to discuss the outcome of this reaction.Special focus and

attention has been given to the amidation reaction as it the primary reaction facing the most

difficulties. Alternative routes are also suggested and the superiority of the method in question is

also established. The data so gathered has been used to give useful facts and statistics of the

reaction and a kinetic model is shown. Later the same series of reaction are taken for plant scale

up and the profitability of the project is shown as viable.


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Index

Sr.no Topic Page

1 Introduction 5

2 Vorinostat- an anti-cancer drug 7

3 Basic Chemistry 8

4Vorinostat previous routes reported

13

5Novel synthesis of Vorinostat

16

6Experimental Procedure

18

7 Results and Discussions 20

8 Kinetic Analysis for Amidation reaction 23

9Block flow diagram

34

10Scale-Up

35

11 Costing 43

12 Conclusion 46

13 References 47


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Introduction

In recent years pharmaceutical and biotech companies have been under increasing pressure to

produce a steady stream of innovative and well differentiated drugs with a reduced cost ofdiscovery and convenient production1. With an aim of increasing productivity of original and

highly pure molecules as potential modulators of therapeutic targets, different and novel

technologies (related to synthesis, workup, and isolation) were developed2. But these methods

still havent proven to be green in the sense of production inputs and environmentally hazardous

outputs for amidation reactions, which still prove to be the grey areas of green chemistry. In

2005, the American chemical society (ACS), Green chemistry institute (GCI)3 and several

leading global pharmaceutical companies developed the ACS GCI Pharmaceutical roundtable

(ACS GCIPR ,hereafter referred to as the Roundtable)4 to encourage innovation while catalyzing

the integration of green chemistry and green engineering into the business of drug discovery,

development and production5. The roundtables mission is to catalyse the implementation of

green chemistry and green engineering in the global pharmaceutical industry.

The process of indentifying key research areas started with the gathering of ideas from all the

involved companies via brainstorming sessions followed by cross company debates then

concluding by a voting exercise.


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As can be seen the amidation reactions and nucleophillic substitution reactions on activated OH

moiety received special attention. Vorinostat was a drug taken as an ideal example of consisting

of both these reactions in subsequent stages. A novel method was devised to use a heterogenoussolid acid catalystsulphated tungstate6developed by P. Chaudhari, K. G. Akamanchi, et al. to

carry out the amidation step in good yields and excellent selectivity. A series of reactions were

conducted to study the nature of this reaction and the subsequent steps were dealt with in a

highly efficient and green way.

Fig. 2

Summary of votes

Fig.1

The process for

identifying and

agreeing on key

research areas


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Vorinostat -an anti-cancer drug

HN

NH

OH

O

O

Vorinostat or suberoylanilidehydroxamic acid(SAHA) is a member of a larger class of compounds that

inhibithistone deacetylases(HDAC). Histone deacetylase inhibitors(HDI) have a broad spectrum

ofepigenetic activities.

Vorinostat is marketed under the nameZolinzafor the treatment ofcutaneous T cell lymphoma(CTCL)when the disease persists, gets worse, or comes back during or after treatment with other medicines.

Vorinostat is chemically named as N-hydroxy-N'-phenyloctanediamide. The empirical formula is

C14H20N2O3. It is a white to light orange powder, very slightly soluble in water, slightly soluble in ethanol,

isopropanol and acetone, freely soluble in dimethyl sulfoxide and insoluble in methylene chloride. It has

no chiral centers and is non-hygroscopic. The pKa of vorinostat was determined to be 9.2.

Vorinostat inhibits the enzymatic activity of histone deacetylases HDAC1, HDAC2 and HDAC3 (Class I)

and HDAC6 (Class II) at nanomolar concentrations (IC50


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Basic Chemistry

By a simple retro synthetic approach the reactants were established as Suberic acid, Aniline and

Hydroxylamine

HN

NH

OH

O

O

NH

O

O

NH

OH

2

O

O

HNOH

Aniline

H2NOH

O

O

HO

OH

Suberic acidH3N

OH Cl

Hydroxylamine Hydrochloride

Reaction scheme. 1

Retrosynthetic

analysis of SAHA


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Amidation

Amidation reactions refer to those reactions where a carboxylic acid and an amine combine with

the elimination of a water molecule to give an amide linkage.

R OH

OHN

R1 R2

+R N

R2

R1

O

Carboxylicacid Amine Amide

-H2O

The mechanism generally accepted and proven consists of nucleophillic attack on the carbon

atom of the carboxylic moiety and the subsequent dehydration to form the amide via a

tetrahedral intermediate.

R N

R2

O

R1

R

O

OH

HN

R1

R2R

O

OH

NR1 R2

H

OH

H

H

O

H

H

R

OH

OH

N

R1 R2

O

H

H H

- H3O

+H3O

- H2O

Reaction scheme.5

General amidation

reaction

Reaction scheme. 6

Acid catalysed

Amidation reaction

mechanism


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A more general observed mechanism would be as follows

R OH

O

+HN

R1 R1R O

O

NR1R2H2

The carboxylic acid reacts with the amine to form an ammonium salt. However because of the lower

reactivity of the carboxylate moiety towards nucleophillic addition elimination8, further reaction needs

relatively stronger conditions and thus seems to be the rate limiting step for the

amide synthesis.

R

O

N

R1

R1

R O

O

NR1R2H2

heat

- H2O

The single most important task of any novel method for amidation would be to overcome the

dehydration step by catalytic or irreversible nucleophillic activation of the carboxylate moiety.

Various methods for amide synthesis have been reported.

Direct methods

The method described by Gooben et al8

using thermal activation for amide synthesis avoiding the use of

catalysts altogether instead using 3A molecular sieves to absorb water is very promising.

R1 OH

O

+ HNR2

R3

3AMolecular sieves

neat,~1600C

-H2O

R1 N

R2

R3

O

Indirect methods

Another method described by Huang et al9 postulates the use of BH3.THF complexes to obtain the

corresponding amides from the parent acid via a triacyloxyborane intermediate.

R1 OH

O

R1 N

R2

R3

O0.35eqBH3.THF (1MinTHF)

toluene, rt,1hrR1 O

O

3

B

1-2eqR2R3NH

reflux,12hr

Reaction scheme. 6

Ammonium salt

formation

Reaction Scheme. 7

Dehydration of

Ammonium salt

Reaction scheme

8. Alternative

reactions to

amidation

Reaction scheme

9. Alternatives

for amidation


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Hydroxamic acid synthesis

Hydroxamic acids of general structure RCONHOH, having R as an organic residue, have

been known since 1869 with the discovery of oxalohydroxamic acid by Lossen. Despite this,

researches on these compounds were lacking until the 1980s, after which an enormous amount of

information has accumulated with respect to their biomedical applications, synthesis, and the

determination of the structures of their metal complexes. Complexation of metal ions by

hydroxamic acids is the starting point of a number of analytical determinations. All hydroxamic

acids, in acid solutions, react with ferric chloride to give rust brown complex salts.These colored

complexes form the basis for the sensitive qualitative and quantitative determination of

carboxylic acids and their derivatives too10.

+R N

H

O

OH

FeCl3

R NH

O

O

Fe

+ 3HCl3

TheN-hydroxycarboxamide group is a key fragment of many siderophores so that a convenient

synthesis of this group is crucial for further progress. A variety of methods have been attempted

for the preparation of hydroxamic acids starting from carboxylic acids. Although some of these

methods are quite efficient for the preparation of substituted hydroxamic acids, the preparation of

the parent compound is still a problem and yields are often moderately unacceptable, in part due

to the low solubility of the parent hydroxylamine hydrochloride in organic solvents.

The most economical way of preparing hydroxamic acid derivatives is the reaction of

hydroxylamine with acid chlorides or esters. Unfortunately, the preparation of acid chlorides is

often tedious. In addition, it is very difficult to avoid further acylation during the reaction with

hydroxylamine. It is not possible to carry out the reaction between hydroxylamine and an ester

under neutral conditions since it always requires a pH>10. Hence, this method is not suitable for

ester derivatives that contain halides, and other base-sensitive groups11.

+R N

H

O

OH

R O

O pH>10

pH=7NH2OH

Reactionscheme. 8

Iron complexes

by Hydroxamic

acids

Reactionscheme. 9

Hydroxamic acid

synthesis from

esters


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In 2000, Reddy and colleagues developed a one-step conversion of carboxylic acid

to hydroxamic acid under neutral pH conditions using ethyl chloroformate as an

activating reagent12.

R NH

O

OH

R OH

O

NH2OHEtOCOCl

Et2O R O

O O

O

Et

Et2O/MeOH

Benzotriazoles are neutral acylating agents, successfully used for the preparation

of amides, oxamides and hydrazides13

.

Giacomelli and coworkers14 have reported a new simple, mild, and high-yielding one-flask

synthesis of hydroxamic acids from carboxylic acids andN-protected amino acids that uses the

very cheap 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride) as a coupling agent.

R NH

O

OH

R OH

O

N

N

N

C

ClCl

,N-methyl morpholine

CH2Cl2,DimethylaminoPyridine(catalyst)NH2OH, r.t,6- 12hours

Reaction

scheme. 10

Hydroxamic

acid synthesis

from

carboxylic

acids

Reaction

scheme. 10

Hydroxamic

acid synthesis

from

carboxylic

acids

Using Benzo

triazoles

Reaction scheme.

11

Hydroxamic acid

synthesis from

carboxylic acids

Using cyanuric

chloride ascoupling agent


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Vorinostat previous routes reported

a. Route 1

Cl

O O

Cl6

HN NH

O O

OH

6

,KOH

NH2OH

(chromatography)

NH2

SAHA

(15-30%)

This was reported by Breslow, Marks et al15. The reaction proposed is to be a one pot synthesis

method using suberoyl chloride treating it with aniline, hydroxylamine and aqueous KOH to give

a yield of 15-30% yield of SAHA (suberoyl anilide hydroxamic acid, Vorinostat). In addition to

lower yields this method also suffers from the significant formation of the dianilide impurity

which is difficult to separate even by chromatographic separation.

b. Route 2

O O

6

HN OH

O O

6

NH2

HO OH

~1900C,10min

(41.7%)

OH

O

O

O

NH2OH.HCl,

NaOMe

MeOH, rt,26hrs (90%)

reflux,22hrs (94%)

Dowex50W-X2acidresininMeOH

SAHA

Reaction

scheme. 10

Reaction

scheme. 11


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This second procedure was reported by Stowell et al16, though the dianilide product was easily separated

but this three step procedure furnished SAHA in only 35% overall yield. Furthermore it involves long

reaction times (up to 28 hours) and harsh reaction conditions (185-1900C). It involves the use of Sodium

metal which is not preferred especially for large scale preparations as in Industry.

c. Route 3O O

6

HN OH

O O

6

NH2

HO OH

SAHA

(CH3CO)2O

Reflux,1hour (94%)

OO O

,THF,rt,0.5hrs

(94%)

1.ClCO2Et,Et3N

0

0

C,10mins

2.NH2OH,MeOHrt,15min(64%)

Though Mai et al17 have managed to produce the intermediate suberanillic acid in good yield the

hydroxamate yield has been low. This furnishes SAHA in only 58.7% overall yield. Furthermore

the reaction intermediate suberic anhydride and reagent ethyl chloroformate are highly sensitive

to moisture and hence not recommended for large scale production.

d. Route 4O O

6

HN O

O O

6

NH2

HO O

NH2OH.HCl,KOH

MeOH, rt,1hrs (90%)

,HOBt,DCC,

DMF,rt,4hrs (88.7%)

HN

HN

O O

OH6

SAHA

Reaction

scheme. 12

Reaction

scheme. 13


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This route reported by Gediya et al18 in 2005 has a very high yield ~80%. It requires milder

conditions and the reaction time is lowered too (~4 hrs). But this technique suffers the obvious

disadvantage of being too mass intensive, 1-hydoxy benzotriazole and dicylcocarbodiimide

being used in 1.2 molar equivalents the atom economy being as low as 42.3% for the first step.

The process also uses DMF as a solvent which is clearly disadvantageous from a green chemistry

point of view. Also another fact not mentioned is that the selectivity of these reagents is low

hence a mono methyl ester of Suberic acid is used which is atleast 60 times costlier than the

parent suberic acid. It can also be stated that suberic acid cannot be used in this process simply

due to the low selectivity and the downstream separations involved and therefore this route is too

cost intensive and impractical at large scales.


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Novel synthesis of Vorinostat

HO OH

O O

6

HN OH

O O

6

NH2

SulphatedTungstate,Toluene,AzeotropicReflux

SubericAcid Suberanillicacid

A novel technique was devised using the Solid acid catalyst Sulphated tungstate to achieve good

yields and excellent selectivity. Traditionally as can be seen from all the routes shown here the

selectivity of dicarboxylic acids has always turned out to be low. Amidation reactions generally

do not occur at mild conditions and using extreme conditions for reaction has always been takenas more feasible. This strategy is successful with mono carboxylic acids. But the problem with

dicarboxylic acids would be that of selective mono amidation. Different coupling agents too

seem to lack selectivity. As the competing groups are both carboxylic acids (and even symmetric

in the case of suberic acid) the problem of differentiating between these two arises.

What was found out in the course of the series of reactions conducted was that Sulphated

tungstate gave almost exclusive yield of the mono anilide product. Even traces of the dianilide

were absent during TLC analysis. A 5g batch was required to be taken to report the yield of

Suberyl dianillide as 1.89%. The corresponding yield of monoanilide was found to be 86.67%.

The selectivity coming to ~97.8% is by far the best result obtained so far amongst any other

synthetic routes available.

HN OH

O O

6

HN O

O O

MeOH,H2SO4

Reflux,2hrs,96%

6

MeOH,KOH,NH2OH.HCl

rt,1hr,90%

HN

NH

O

O

OH

SAHA

MethylSuberanillate

Reaction

scheme. 13

Reaction

scheme. 14


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The rest of the succeeding reactions are shown above. These represent the standard method of

synthesis of hydroxamic acids from the corresponding esters. The yield is very high (90%)

expectedly with the major byproduct being Suberanillic acid itself which is easily separated from

the hydroxamic acid.

Overall yield of the reaction can be calculated as 74.88 ~75% with a selectivity of 97.8%.


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Experimental Procedure

Suberanillic acid

Suberic acid (1 g, 5.747 mmoles, 1 eq) was placed in a 50 ml round bottom flask along with

sulphated tungstate catalyst (0.142g, 10% w/W) and dry toluene (20 ml) was poured along with

a magnetic bar. The round bottom flask was placed in an oil bath and a dean stark trap attached

with a reflux condenser. Sufficient toluene was filled into the trap so as to obtain a suitable

reflux. Aniline (0.53 ml, 5.75 mmoles, 1 eq) was added to the mixture as it was stirred

continuously. The mixture was refluxed for 12 hrs. The mixture was then cooled and the

toluene evaporated under vacuo. The residue was taken up in ethyl acetate (50 ml) and the

catalyst was filtered under vacuum. The solvent was evaporated under vacuo and the solid was

stirred with an aqueous solution of KOH (50 ml, 10% w/V) for hr. The solution was filtered

and the filtrate was cooled to 100C. HCl solution (20 ml, 30% w/V) was added to the filtrate

dropwise. The precipitate was filtered under vacuum and kept at 400C overnight for drying. The

Suberanillic acid so obtained was collected and weighed (1 g, yield 69.8%). The melting point

was found to be 122-1230C. IR (KBr Disc) 3441, 3326, 2922, 2864, 1696, 1657, 1527, 1417, 1330,

1253, 1181, 931, 753, 690 cm-1

.

Methyl Suberanillate

The Suberanillic acid (0.4g, 1.6 mmoles) was dissolved in anhydrous Methanol (10 ml, 312.5

mmoles) and Sulphuric acid (0.1ml) was added and the mixture refluxed for 2 hrs in an oil bath.

The mixture was cooled and the solvent evaporated by vacuo. The residue was taken up in ethyl

acetate (10ml) and the washed with saturated Sodium Bicarbonate solution (10 ml). The organic

layer was dried over Na2SO4 and evaporated to yield the ester (0.394g, yield 93.22%).mp 64-

65

0

C. IR (KBr Disc) 3302, 3048, 2927, 2855, 1731, 1659, 1599, 1536, 1500, 1447, 1379, 1331,1250, 1173, 1100, 1014, 965.9, 883, 720, 691, 605, 504cm-1. H1-NMR (60 MHz, CCl4)- 7.671,

7.537, 7.411, 7.317, 7.20, 7.073, 6.94, 3.604 (s, 3H), 2.231, 2.13, 1.39.


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Suberoyl anillide hydroxamic acid (SAHA)

Hydroxylamine hydrochloride (4.859g, 69.92 mmoles) was dissolved in methanol (12 ml) and

mixed with KOH (3.91g, 69.92 mmoles) in methanol (22 ml) at 400C and cooled to 00C and was

filtered. Methyl suberanillate (1g, 3.80 mmoles) was added to the filtrate along with KOH(0.32g, 5.699 mmoles) and the mixture was stirred at room temperature for an hour. The mixture

was added to stirring cold water (122 ml) and the pH adjusted to 7 by acetic acid. The precipitate

was filtered off at vacuum and the resulting product was dried overnight at 400C to yield SAHA

(yield 0.9g, 90%).mp 160-1610c. IR (KBr disc) 3431, 3336,2929,1630,1571 cm-1.


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Results and Discussions

Amidation

HO OH

O O

6

HN OH

O O

6

NH2

SulphatedTungstate,Toluene,AzeotropicReflux

SubericAcid Suberanillicacid

HN

O O

HN

6

SuberoylDianilide

+

Sr.no Acid Base Catalyst

Yield of

Mono

Product

Yield of

Di

product

Time Solvent Comments

Wt

gEq

Vol

mlEq % w/W % % Hrs

1 1 1 0.54 1 0 16.77 0 12Toluene

Varying

amounts of

catalyst

2 1 1 0.59 1.1 5 69.85 0 12Toluene

3 1 1 0.54 1 10 69.85 0 12Toluene

4 1 1 0.54 1 20 69.85 0 12Toluene

5 5 1 2.94 1.1 10 86.92 1.87 12Toluene

Mass reaction

6 1 1 0.54 1 10 69.85 0 12 Toluene

Varying

Concentration

s of aniline

7 1 1 0.81 1.5 10 69.85 0 12Toluene

8 1 1 1.07 2 10 69.85 0 12Toluene

9 1 1 0.54 1 10 0 0 12 ChloroformLow

Temperature

10 1 1 0.54 1 10 47.92 0 18 Toluene Normal reflux

11 1 1 0.59 1.1 10 47.92 5.01 20 mins -

Neat reactions

At 145-1500C

12 1 1 0.81 1.5 10 48.9 6.76 20 mins -

13 1 1 1.07 2 10 49.59 6.91 20 mins -

14 1 1 1.61 3 10 49.59 7.14 20 mins -

15 1 1 0.54 1 10 61.47 10.14 12 Toluene50% w/W

silica

Reaction scheme. 15


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The table provides with many definite facts about theSulphated tungstatecatalyst.

The temperature for reaction seems to be necessarily over 1000C the reaction to takeplace. This is demonstrated from the fact that that the reactions in Chloroform reflux at

760

C does not proceed at all. It is also observed that that without the catalyst the reaction proceeds poorly with the

yield less than 20%.

A mixture of 10% w/W of catalyst and 50% w/W Silica was taken as a catalytic mixture.This reaction showed higher yields for the Di-substituted product and slightly lower yield

of mono-substituted product.

A series of solvent-less reactions were taken up (neat reactions) at a temperature of 145-1500C. These showed yields comparable to the previous procedures but the yields of the

Di-substituted product increased.

The above graph clearly shows the increasing trend of yield of mono product withincreasing amounts of catalyst. The optimum concentration of catalyst for this reaction

lies in the range of 5-10% w/W.

The other interesting trend shown here is the eventual decrease in yield with furtherincrease in catalyst concentration. This phenomenon can be attributed to the fact that the

catalyst forms a complex with aniline itself at such high concentrations hence decreasing

the overall yield.

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25

YieldofMonosubstit

utedproduct%

Catalyst %w/W

Yields Vs Catalystfor standard reaction

Yields Vs Catalyst


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All the reactions above were done at standard conditions with 1:1 equivalent ratios ofSuberic acid and Aniline.

The above graph shows the yield of mono product compared to the equivalents of Anilineused.

The fact that the yield remains stable from 1:1 mol.equivalents to 1:2 mol.equivalents ofaniline indicates the robustness of the process and the flexibility.

Neat reactions also show a robustness of yield from an even wider range of 1:1 to 1:3mol. Equivalents of aniline.

0

20

40

60

80

0 0.5 1 1.5 2 2.5

YieldofMonosubstituted

product

Equivalents of aniline

Eq Aniline Vs Yields

for standard reaction

Eq Aniline Vs Yields

0

10

20

30

40

50

60

0 1 2 3 4

YieldofMonoProduct

Equivalents of Aniline

Yield Vs Equivalents of aniline for

Neat reaction

Yield of Mono product

yield of di product


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Kinetic Analysis for Amidation reaction19

It can be stated that the amidation reaction takes place in three distinct steps

HO OH2

O O

6

6

NH2

+

+

HO O

O O

NH3

6

HO O

O O

NH3HN

6

OH

OO

HN

6

OH

OO

HN

6

HN

OO

Ksalt

Kmono

Kdi

Condensation

NH2

saltformation

This can be simply written as

S +A Salt

Salt Mono

Pr Di

The kinetics can be developed easily from the assumption that the steady state concentration of

the Ammonium salt is constant

Thus

d[S]/dt=Ksalt[A][S] ..assuming [A]=[S] and solving for [S] taking [So] as the initial

concentration

[S]=[So]/([So]Ksaltt +1)

Where S=Suberic Acid

A=Aniline

Salt=Ammonium salt

Mono =Mono Product (suberanillic acid)

Di =Di product (suberoyl Dianilide)


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d[salt]/dt=-kmono[salt] +Ksalt[A][S] and solving for [salt]

[salt]=c*e-Kmono*(t+1/a)*Ei(Kmono(t+1/a))/a - c*e

-kmono/a*Ei(Kmono/a)e-Kmonot/a

Now assuming d[salt]/dt=0

Deriving for [mono]

[mono]=Ksalt[So]2*(t/(1+[So]Ksaltt))

And Hence [Di]=Kdi*Ksalt*[So]3*{log(1+a*t)+1/(1+a*t)-1}/a2

Assuming 80% concentration of Mono product & 2% concentration of Di product after 12 hrs

the corresponding rate constants can be calculated as

Kmono| (383 K, 12 hrs) =4.10 x 10-5 Ltr/Mol.sec

KDi| (383 K, 12hrs) =5.73 x 10-7Ltr/Mol.sec

Kmono| (423 K, 20 mins, neat) =3.75 x 10-4 Ltr/Mol.sec

KDi| (423 K, 20 mins, neat) =5.22 x 10-6Ltr/Mol.sec

From the Arrhenius equation the corresponding Activation Energies of reaction can be calculated

-0.5

0

0.5

1

1.5

2

2.5

0 10000 20000 30000 40000 50000 60000

ConcentrationsinMoles/Ltr

Time in seconds

Concentrations of Suberic acid, ammoninum salt and mono product Vs time

Ammonium salt Concentration

Mono product concentration

Suberic acid concentration

Di Product concentration

Where c= [So]2*Ksalt

a=[So]*Ksalt

and Ei= Exponential Integral


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Ln(k1/k2)=-Ea/RT*(1/T1-1/T2) Where Ea is the activation energy and R is the universal gas

constant

Ea| (Mono product) =74.5 KJ/mol

Ea| (Di product) =84.9 KJ/mol

The Variation of rate constants of both these reactions can be seen in graph

Selectivity of Reaction

During the course of the amidation reactions it was repeatedly observed that the yield of the

mono product was significantly greater than the Di product even though Kinetic studies without

the catalyst showed a lower overall yield. The reason for this observation was unknown and

further experimentation needs to be carried out to put forward a theory of selectivity.

Mean while it was hypothesized that since suberic acid has two corresponding pKa for the two

carboxylic groups the second acidic proton was not acidic enough to cause a reaction and hence

selectivity of reaction was seen. It was also observed that the catalyst catalyses this particular

step and hence raises the yield of the mono product much more than the Di product.

0

0.001

0.002

0.003

0.004

0.005

0.006

0 100 200 300 400 500 600

RateConstantsinL

tr/Mol.sec

Temperature in K

Rate constants Vs Temperature

Mono reaction

Di reaction


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HO OH2

O O

6

6

NH2

+HO O

O O

NH3

pKa4.52

+

HN

6

OH

OO

HN

6

OO

NH2 O

NH3pKa5.40

When the reaction was carried out at 1900c without any catalyst by stowell et al it was seen that

the yield of the mono product was 47% while the yield of Di anilide was 11%. When the reaction

was conducted here at 1500C in neat conditions the yield of the mono product was 48% and of

the Di anilide was 5%. These observations clearly show the superiority of the catalyst as well as

the efficiency of the novel procedure developed.

TLC Analysis

The TLC analysis showed a particular problem. The reactant Suberic acid was seen to be

completely invisible under UV light and immune to oxidizing agents like Potassium

permanganate and p-Anisaldehyde which are the normal TLC visualization agents.

A new visualization agent was used. This was Methyl Red basically used as an indicator in

solution; it also served as an excellent acid indicator changing colour in response to an acid of

pKa


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Aniline

MonoProduct

ResidualAniline

Another Visualization agent used was Xylenol Orange

AnilineRf0.8

MonoProductRf0.4

ResidualAniline

Before dipping in

Methyl Red

solution

Eluent 30% EtOAc

in Hexane

After Dipping in

Methyl Red Solution

Suberic Acid Rf 0.36

Before dipping in

Xylenol Orange

solution (under UV)

Eluent 30% EtOAc in

Hexane

After treatment of

Xylenol Orange


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O

O

OH

OH

NH2

O

O

N

Ninhydrin Colouredproduct

N N

OH

N

O

After treatment with

Ninhydrin

Xylenol Orange Indicator

Colour change due to pH

sensitive sulphonate ester

Ninhydrin test

for Aniline

Methyl red Indicator

pH 4.4 6.2

Red to yellow


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AnilineRf0.8 M

onoProductRf0.4

Diproduct

Rf0.6

SubericAcidRf0.36SeenbyMethylRedIndicator

MonoProduct

Rf0.4

DiProductRf0.6

MethylSuberanillate(ester)Rf0.72

Vorinostat(SAHA)Rf0.32

TLC taken after final step

Shows all the products

obtained

TLC analysis after final step

shows all the obtained

products

Eluent 30% EtOAc in Hexane

TLC after treatment with FeCl3

solution

30% EtOAc in Hexane


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IR and NMR analysis


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Block flow diagram

Amidation Condensation

Hot

Filtration

Neutralization

Filtration Drying Esterification

FiltrationSolventevaporation/

Drying

Hydroxamate

Synthesis

Solvent

evaporation

Filtration/

NaHCO3 wash

Drying

Toluene

Suberic acid

Sulphated

Tungstate

Aniline

MeOH

Sulphated

Tungstate

Catalyst Recovery

MeOHHydroxylamine HCL

KOH

Acetic Acid10% NaHCO3

Effluent Treatment

Catalyst

Recovery

Condensed

water

Effluent

treatment

Vorinostat SAHASolventrecovery

Recovered

Toluene

Effluent

NaOH dissolution

Filter

Di anilide impurity

HCl

acid

Methanol Recovered

Fig. 4

BFD


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Scale-Up

Basis: - Batch size 0f 1000kg of SAHA, all sizing of equipment and costing will be on this basis.

Amidation

Amidation step needs to be carried out in a S.S reactor. A heat exchanger and a condenser are

fitted in series where the lighter stream (toluene) will flow back to the reactor and the heavier

stream (water) will flow out during the azeotropic reflux. Although the concentration of the

azeotrope (water/toluene) is water(20%):toluene(80%) and temperature of azeotropic boiling is

840C the mixture will tend to boil at a temperature higher than 1000C, super heated steam is

preferred as an ideal heating medium.

Fig. 5

Total mass

balance

Amidation


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Mass Balance

Input Weight Kg Output Weight kg

Suberic acid 1000 Suberanillic acid (80% yield) 1144.8

Aniline 588 Suber dianilide 42.99

Toluene 2000 ltrs Water 85

Sulphated Tungstate 177 Toluene recovered 2000 ltrs

Unreacted Suberic acid 178

Catalyst recovered (95%

recovery)

168

Aniline unreacted 148.6

Total Mass IN 3498.8 kg Total mass OUT 3501.2 kg

Specifications for Reactor Design

Parameter Calculated value or assumed value

Volume (capacity) 4 m

Type and MOC Standard Stirred tank reactor MOC S.S with

glass lining Temperature upto 1500c and

pressure 2 atm

Vacuum 560mm Hg

Diameter 1.72 m

Height 1.72 m

No. of baffles 6

Baffle width 0.17 m

Stirrer type and diameter Axial flow propeller Diameter 0.6 m pitch 1.0

Clearance 0.6m (from bottom of reactor)

Motor capacity 80 KW DC supply

Heating supply Jacket supply superheated steam

Cooling supply Jacketed supply of Cold water

Foam breaker Diameter 0.7 m curved vane type


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Operating variables


Temperature 110 C (maximum value)

Pressure 1 atm

Critical speed of impeller 2 rps

Reynolds number 106280

Froude Number 0.0733

Reflux rate 150 ltr/hr

Mass flux of toluene 130 kg/hr ( 100% toluene assumption)

Heat flux removed 53.64*10 3 KJ/hr

Heat load on condenser 69.17* 10 3 KJ/hr=16.5 * 10 3 Kcal/hr

Flow rate of cooling water (condenser) 236 Kg/hr

Cooling water requirement 66 TR

Specifications of Heat exchanger/ Condensers


Type and capacity Shell and Tube 1:1 420 ltrs

MOC Copper tubes in a S.S shell

Tube diameters 3/4 od (assumed)

Number of tubes 265

Shell diameter 0.5 m

Tube length 2.4 m

Total area for heat exchange 75.92 m


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Filtration


Type and capacity Agitated Nutche filter capacity 4 m

Filter area 14 m

RPM 5 RPM

Agitator drive 55 KW

Drying


Type and capacity Fluidized bed dryer 1500 kgMOC SS-304

Hot air generator Radiation working on steam

Hot air specifications 70C RH 10%

Esterification

Esterification reaction uses excess of methanol and a solid acid catalyst (Sulphated Tungstate) in

this case to give high yields of product. It relies on continuous reflux of methanol to drive the

reaction forward.

Fig. 6

Total mass

balance

Esterification


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Mass Balance


Suberic acid 1144.8 Methyl Suberanillate (96%

yield)

1160.8

Methanol 1000 ltrs Water 80

Sulphated Tungstate 100 Catalyst recovered (95%

recovery)

95

Methanol Recovered 850 ltrs

Total Mass IN 2035.8 kg Total mass OUT 2008.15 kg

Reactor Specifications


Volume (capacity) 1.5 m



pressure 2 atm

Vacuum 560mm Hg

Diameter 1.24 m

Height 1.24 m

No. of baffles 6

Baffle width 0.12 m

Stirrer type and diameter Axial flow propeller Diameter 0.42 m pitch 1.0



Heating supply Jacket supply superheated steam

Cooling supply Jacketed supply of Cold water


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Temperature 65 C (maximum value)

Pressure 1 atm

Critical speed of impeller 44 rpm

Reynolds number 106280

Froude Number 0.0733

Reflux rate 50 ltr/hr

Mass flux of toluene 39.6 kg/hr ( 100% methanol assumption)

Heat flux removed 43.5*10 3 KJ/hr

Heat load on condenser 46.22* 10 3 KJ/hr=11 * 10 3 Kcal/hr

Flow rate of cooling water (condenser) 440 Kg/hr

Cooling water requirement 15.3 TR

Specifications of Heat exchanger/ Condensers


Type and capacity Shell and Tube 1:1 420 ltrs

MOC Copper tubes in a S.S shell

Tube diameters 3/4 od (assumed)

Number of tubes 265

Shell diameter 0.5 m

Tube length 2.4 m

Total area for heat exchange 75.92 m

Drying


Type and capacity Fluidized bed dryer 1500 kg

MOC SS-304



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Hydroxamic acid synthesis

Hydoxamic acid synthesis is possibly a dangerous reaction and explosive hence it is essential to

provide a efficient cooling system cooling system to avoid hazards and risks of explosion.

Mass Balance


Methyl Suberanillate 1160.8 Methyl Suberanillate (96%

yield)

1048.7

Methanol 1000 ltrs Water effluent 1631.9

Hydroxylamine

Hydrochloride

613.5 Methanol Recovered 1000 ltrs

KOH 494.310% NaHCO3 362

Acetic acid 50

Total Mass IN 3471.6 kg Total mass OUT 3470 kg

Fig. 6

Total mass

balance

Hydroxamic

acid synthesis


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Reactor Specifications


Volume (capacity) 2m



pressure 2 atm

Vacuum 560mm Hg

Diameter 1.36 m

Height 1.36 m

No. of baffles 6

Baffle width 0.13 mStirrer type and diameter Axial flow propeller Diameter 0. 45 m pitch

1.0



Cooling supply Jacketed supply and cooling coils of Cold

water

Drying


Type and capacity Fluidized bed dryer 1500 kg

MOC SS-304

Hot air generator Radiation working on steam



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Costing

Equipment

Equipment Units Unit price Lakhrupees

Cost Lakh rupees

Fluid bed dryers 1.5 m 3 4.5 13.5

Batch reactor S.S glass

lined capacity 4 m3

1 29.4 29.4

Batch reactor S.S glass

lined capacity 1.5 m3

1 11.65 11.65

Batch reactor S.S-316

glass lined capacity 2 m3

1 13.59 13.59

Shell-tube Heat

Exchanger

Capacity 420 ltrs

2 16.11 32.22

Agitated Nutche filters 3 5.71 17.14

Piping costs - - 28

Electrical wiring cost - - 29.6

Boiler costs 1 313 313

N2 plant 1 25.2 25.2

Vaccuum pumps 2 12.82 25.64

Cooling tower cost 2 9.58 19.16

Refrigeration cost 1 5.67 5.67

Storage tank 60 m 1 13.32 13.32

Storage tank 40 m 3 13.68 41.04

Pumps Inline 4 4.36 17.46

Total 635.6


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Inventory (per batch, 1000 kg SAHA)

Material Unit cost per tonne Requirement in

tonnes

Total Rs

Suberic acid 45000 1 45000

Aniline 69255 0.588 4072

Toluene 18456 1.733 31984

Sulphated Tungstate 50000 0.277 13850

Methanol 15170 1.58 23960

KOH 14000 0.494 6916

NaOH 15310 0.184

Hydroxylamine

Hydrochloride

157500 0.82 129150

NaHCO3 16403 0.2 3286

Water - - -

Acetic acid 25000 0.60 150000

HCl 4000 0.25 1000

Total 411918=4.2 lakhs

Sales

Product Sales projections Unit sale price Total revenue

Vorinostat 50 tonnes/year 0.4 lakhs/kg 65600 lakh Rs


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Profit and profit margin

Profit=Revenue Cost of equipment - cost of material per batch* no. of batches Land cost

General expenses (salaries and wages) office expenses Interests.

=20000 635.6 4.2*105 1000 650

=17504.44 Lakhs per annum

Correcting for errors reducing by 20% and cutting tax rate at 12.5%

=12253 Lakhs per annum

=122.5 crores per annum

Along with these a tender has to be floated for an Effluent treatment plant outside the battery

limit. The effluent plant must be capable of handling extremely alkaline and acidic pH as well.

The BOD and COD emissions are subject to local limits and must be strictly adhered to.

Location of Plant: Goa

Rationale of Choice:

Goa has many pharmaceutical plants and has been developing rapidly over the years Excellent Infrastructure is in place and cheap land and labour is easily available Favourable stance of local government and awareness amongst the people for green

engineering will only increase popularity.


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Conclusion

The experimental work performed and the scale-up analysis shows that very successful chemical

project can be visualized. Sulphated tungstate as a solid acid catalyst is extremely versatile andtends to be inexpensive and reusable at plant scale up. The reactions performed here within hold

significant promise of enhanced selectivity of such dicarboxylic condensation reactions. Not only

has the yield enhanced but also a high selectivity has been achieved unmatched by any other

synthetic method in use today. It can be interpreted from the analysis that the foremost problem

awaiting a solution by the industry is near completion. The formation of the hydroxamate salt

still represents a particular problem but further research and kinetic modeling can uncover more

facts and provide a unique mechanism. The lab hours and experiments conducted have been

extremely fruitful and have provided a rich research experience.


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References

1. Elena Riva., et al ,Efficient Continuous Flow Synthesis of Hydroxamic Acids andSuberoylanilide Hydroxamic Acid Preparation,J. Org. Chem.2009, 74, 35403543

2. (a) Chighine, A.; Seche, G.; Bradley, M. Drug Discovery Today2007, 12, 459464. (b)Kirshining, A.; Solodenko, W.; Mannecke, K,Chem.-Eur. J. 2006, 12, 59725990.

3. www.greenchemistryinstitute.org4. www.chemistry.org/greenchemistryinstitute/pharma_roundtable.html5. David J. C. Constable, Peter J. Dunn, et al, Key green chemistry research areas- a

perspective from pharmaceutical manufacturers, Green Chem.2007, 9, 411-420.

6. Pramod S. Chaudhari, Suresh D. Salim, Ravindra V. Sawant and Krishnacharya G.Akamanchi Sulfated tungstate: a new solid heterogeneous catalyst for amide

synthesis, Green Chem., 2010, 12, 1707-1710

7. Prescribing information, Zolinza (reg. trademark, vorinostat), Merck, Initial U.S. approval2006

8. L.K. Gooben et al, The thermal activation of Carboxylic acid revisited, Synthesis, 2009,No.1, pp160-164

9. Z. Huang, J. R. Reilly, R. N. Buckle, An Efficient Synthesis of Amides and Esters viaTriacyloxyboranes, Synlett, 2007, 1026-1030.

10.T.W. Solomons, C.B. Fryhle,Carboxylic acids and their derivatives. NucleophillicAddition-Elimination at the Acyl Carbon, Organic Chemistry, 8

thedition, 2004, 813-877

11.Synthesis of oximes and hydroxamic acids, The chemistry of Hydroxylamines, Oximesand Hydroxamic Acids, A. Porcheddu and G. Giacomelli, 2009, 164-226.

12.A. S. Reddy, M. S. Kumar and G. R. Reddy, A mild oxidation method of hydroxamicacids: efficient trapping of acyl nitroso intermediates, Tetrahedron Lett., 2000, 41,

6285.

13.A. R. Katritzky, H.-Y. He and K. Suzuki, N-Acylbenzotriazoles: Neutral Acylating Reagentsfor the Preparation of Primary, Secondary, and Tertiary Amides,J. Org. Chem., 2000,

65, 8210.


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14.G. Giacomelli,* A. Porcheddu, M. Salaris, Simple One-Flask Method for the Preparationof Hydroxamic Acids, Org. Lett.,2003, Vol. 5, No. 15, 2715-271727

15.R. Breslowet al, Novel potent inducers of terminal differentiation and methodsthereof.PTC Int.Appl.WO 93/07148, April 15, 1993

16.J.C. Stowell et al , The synthesis of N-Hydroxy-N1-phenyloctanediamide and itsinhibitory effect on proliferation of AXC rat prostate cancer cells,J. Med. Chem,

1995,38,1411-1413

17.A. Mai et al , A new facile and expeditious synthesis of n-hydroxy-n'-phenyloctanediamide, a potent inducer of terminal cytodifferentiation, OPPI briefs,

2001, 33, 391-394

18.L.K .Gediya et al, A New simple and high-yield synthesis of Suberoylanilide Hydroxamicacid and Its inhibitory effect alone or in combination with Retinoids on Proliferation of

Human Prostate Cancer Cells,J. Med. Chem, 2005, 48, 5047-5051

19.Further calculations and kinetic modeling done with help of Mathematica 8 andMicrosoft excel.

Final Report Amit Nayak

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