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Rapid Compound Production:Microwave-Assisted Synthesis, Workup and Purification

Shahnaz Ghassemi Ph.D.

User Group Meeting-Boston

2

Topics

• Microwave-assisted organic synthesis– Advantages– Scope

• Solid supported reagents and scavengers– Advantages in solution phase synthesis

• Key Transformations using solid-supported reagents/scavengers

AmidationAryl-aryl bond formation (Suzuki Reaction)AlkylationOxidationReductive aminationAcid catalyzed Reactions Base Catalyzed reaction

3

Br

OMeMeO

+

PalladacycleNaOAc / LiCl

K2CO3 / H2O

Heck

Microwave190 oC, 1 min, 89 %

Conventional80 oC, 16h, 82 %

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Advantages of using microwave heating in organometallic coupling

4

Advantages of using microwave heatingin Aminocarbonylations

CNR2R3

O

R1

XR1

PhNH2CO g (10 atm)PdCl2(PPh3)2

120 °C 24 h

Br

R R

NHPh

O

HNR2R3Mo(CO)6

Pd(OAc)2, DBU, [Imidazole]

100-150 °C8-15 min.

Conventional

Improved Mo(CO)6Microwave

ONH

OEt

O

H3CO

H3CONHR

O

Eur.Pat.Appl., 831095, 25 Mar 1998Wannberg, J.; Larhed, M., JOC, 2003; 68(14); 5750-5753Wu, X.; Ronn, R.; Gossas, T.; Larhed, M. JOC, 2005; 70(8); 3094-3098John T. Gupton, Edith J. Banner, et al. Tetrahedron, 2006 62, 35, 243-8255

HNR2R3 = anilines, tert-butylamine, and free amino acids

alkaloids Rigidin and Rigidin E

95-100%

5

Will Microwave be the “heating Mantle” of the 21st

Century??

6

Conventional Heating

7

Microwave vs Conventional Heating

Microwave Heating

8

Domino Ring Closing Metathesis

Efskind J., Undheim, K. Tetrahedron Lett. 2003, 14, 2837-2839.

Grubbs Catalyst Toluene

160 oC / 20 min

100 % conversionN

NMeO

N

N OMe

MeO OMe N

NMeO

OMeN

N OMe

MeO

50-80% less catalyst compared to conventional

Advantage of MAOS Organometalic Reactions

9

• Most room temperature & elevated temperature reactions

• Reactions in Polar and Non-polar solvents

• Metal catalyzed and gaseous reactions

REACTION O

PTIMIZ

ATION

IS K

EY TO SUCCESS

SCOPE OF MICROWAVE SYNTHESIS

• Reactions with solid-supported reagents

http://www.ed.ac.uk/~ah05/microwave.html

http://www.ed.ac.uk/~ah05/microwave.html

10

What Slows Down Drug Discovery?

Work-up Purification Evaporation

Bottlenecks in Drug Discovery

11

Solid-bound reagents and scavengers

Can Solid-bound reagents and scavengers eliminate traditional work-up and purification

step??

Solid-Bound Reagents & ScavengersMode of Action

Rgt1.5eq S1 + S2

R gt-sp e nt

P + 0 .5 e q S 1

Scvngr

ScvngrRgt-spent S1

Product

Solution Phase Synthesis• Conventional• Microwave-assisted

• Filtration• Evaporation

13

Professor Proves: Time is Money,

Time is actually money

14

Biotage Resin Reagents

Bound Reagent Solution Analog Application

PS-TsCl p-toluenesulfonyl chloride Catch & Release

MP-TsOH p-toluenesulfonic acid Catch & Release

PS-DIEA Hindered tertiary amine Amine base

PS-NMM N-methyl morpholine Non-benzylic base

PS-TBD TBD Strong Base

PS-DMAP DMAP Catalyst, Catch & Release

MP-Carbonate Ammonium carbonate Base, Catch & Release

MP-Borohydride Sodium borohydride Reducing Agent

MP-Cyanoborohydride Sodium cyanoborohydride Reducing agent

MP-Triacetoxyborohydride Sodium triacetoxy borohydride Reducing agent

MP-TsO-TEMPO TEMPO Oxidizing Agent

PS-Carbodiimide DCC Coupling Agent

PS-HOBt (HL) HOBt Coupling agent

PS-Triphenylphosphine Triphenylphosphine Mitsunobu/Wittig/Halogenation

PS-PPh3-Pd Triphenylphosphine Pd(0) Palladium Catalyst

15

ISOLUTE® Si-Triamine

BIOTAGE INTRODUCESBIOTAGE INTRODUCESSilicaSilica--supported Reagents/Scavengerssupported Reagents/Scavengers

ISOLUTE® Si-Carbonate

ISOLUTE® Si-Ts-Hydrazide

ISOLUTE® Si-Thiol

ISOLUTE® Si-Propylsulfonic acid (SCX-2)

ISOLUTE® Si-EthylPhenyl sulfonic acid (SCX-3)

N+ (CO3)-20.5

Si

SHSi

NH

HN

NH2Si

S

O

O

NHNH2

Si

SSiO

O

O-

S

O

O

O-Si

NEW!NEW!

NNH2

Si

NH2

ISOLUTE® Si-Trisamine

16

Fast workflow

Synthesis Work-up Evaporation

•Simplifies workflow and enhances the rate of drug discovery

17

Key Microwave-Assisted TransformationsSolid-supported reagents/Scavengers

• Amidation• Aryl-aryl bond formation (Suzuki Reaction)• Alkylation• Oxidation• Reductive amination• Acid catalyzed Reactions • Base Catalyzed reaction

18

PS-CarbodiimideAmide-Coupling

O N=C=N

PS-Carbodiimide

Bound variant of DCC

• Stable to extended storage (25 days at RT, >6 months at 4 ºC)

• Urea byproduct Resin bound and easily removed

PS

19

Rapid Acylation & Purification of Amines

NH3+

SO

OO-

+HOBt, DIEA

µW 100 ºC, 5 Min.DCM

AU

0.00

0.10

0.20

0.30

0.40

0.50

Minutes2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00

2.38

7

8.05

3HOBt+

Acid Product

Reaction Mixture

AU

0.00

0.20

0.40

0.60

0.80

1.00

1.20

Minutes2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00

2.50

1

7.96

7

Product

O

OH

I

NH

OI

N=C=NPS

99% yield98 % Purity

NH

OI

NN

NOH

O

OH

I+

Si

N+ (CO3)0.5

-2Si

Sauer,D., Kalvin, D., Phelan, K., Org. Lett. 2003, 5, 4721

20

PS-DIEA

PS-DIEA

NiPr

iPr

DIEA equivalent on Solid support

PS

21

Rapid purification

59% yield97 % Purity

N

O

Br

NH

N+ (CO3 )0.5

-2

SiSi

NiPr

iPrPS

+NH

OH

O

Br

N

O

Br

NH+

HATU,µW 110-150 ºC

6-12 min.

N

O

Br

SO 3H

SiSi

Ghassemi, S. ACS, Atlanta, GA, March 2006

22

289.959150 ºC, 12 min.6

365.857150 ºC, 12 min.5

299.990110 ºC, 6 min.4

344.997110 ºC, 6 min.3

379.991110 ºC, 6 min.2

31699110 ºC, 6 min.1

MSM+1b

% YieldaConditionAmidesAmine

289.959150 ºC, 12 min.6

365.857150 ºC, 12 min.5

299.990110 ºC, 6 min.4

344.997110 ºC, 6 min.3

379.991110 ºC, 6 min.2

31699110 ºC, 6 min.1

MSM+1b

% YieldaConditionAmidesAmine

NH

NH

NHN

NHO

O

NH

NH

N

OBr

N

OBr

N

O

NBr

BrN

O

OO

N

OBr

N

OBr

Rapid Acylation & Purification Less Reactive Aromatic Amines

DIEAHATU,O

OHXNH

R1

R2

+R2N

O

R1XµW 110-150 ºC

6-12 min.

N+

(CO3 )0.5-2

PS SiPS Si

23



24

Polymer-Supported PdRapid Microwave Assisted Suzuki Reaction

PS-PPh3-Pd

P PdLnPS

• Use:Palladium catalyzed C-C coupling

• Advantage over Tetrakis palladiumStable to air, light and moistureNo “Hot Spot” – minimizes vial breakage in MAOSShelf-stable at room temperature Simplified product isolationLow Pd levels in product (< 100ppm)

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N

O

O2NN

O

NO2NN

OO

OO2N

N

O

O2NN

O

O2NN

O

O2N

N

O

O

N

O

N

N

O

O2NN

OBr

BOH

OHO2N

+

PS-PPh3-Pd

CsCO3

µW 130 ºC10 Min.

N+

(CO3 )0.5-2

SiPS

Si

% Yield 85-99

Polymer-Supported Pd and Si-Carbonate Rapid Synthesis & Isolation of aryl carboxamides

26



27

NN

N

• PS-bicyclic guanidine (1,5,7- triazabicyclo[4.4.0]dec-5-ene )

• Stronger base than PS-DIEA, PS-NMM

• Deprotonate moderately acidic hydrogens, (pKa 13-15)

• Applications Include:Alkylation of phenols, amines, active methyleneEsterification of carboxylic acids

Morrissey, M.; Mohan, R.; Xu, W. Tetrahedron Lett. 1997, 38,7337

Organ, M.G.; Dixon, C.E. Biotechnol. Bioeng. (Comb. Chem) 2000, 71, 71-77

PS-TBD

PS

PS-TBD

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PS-TBD: Williamson Ether SynthesisCatch and Release

R3-Br

OHR PS

N+

N

N

H O-

RNN

N

PS

OR3

Catch ReleaseMeCN hrs

Purity % Yield %

100 91

100 90

100 95

100 90

100 85

MeO O

O

BrBr

OBr

O7

OBr

29

PS-TBDGrubbs Catalyst Scavenger

3 mL of 1000 ppm solution of Crubbs catalyst was treated with 0.5 g of PS-TBD for 2 hrs RT.<1 Ru was left in solution

P

RuH

Cl

Cl

P

100 ppm <1 ppm

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ISOLUTE® Si-Thiol

ISOLUTE® Si-Thiol

SHSi

• ISOLUTE Si-Thiol is the silica-bonded equivalent of 1-propanethiol

• Applications Include:Electrophiles scavenger such as alkyl-, benzyl- and allyl-halides, acid chlorides, isocyanatesMetal scavenger eg Pd, Pt, Cu, Hg, Ag and Pb

31

ISOLUTE® Si-ThiolElectrophiles Scavenger

Reaction mixture

AU

0 . 0 0

0 . 0 2

0 . 0 4

0 . 0 6

0 . 0 8

M in u t e s2 . 0 0 4 . 0 0 6 . 0 0 8 . 0 0 1 0 . 0 0

3.98

8

5.66

6

AU

0 . 0 0

0 . 0 5

0 . 1 0

0 . 1 5

M in u t e s2 . 0 0 4 . 0 0 6 . 0 0 8 . 0 0

3.98

3

Product after treating with

Si-Thiol

DIEA, 3 eqTHF

RT. 15 minMin.

N

OMe

O

NH

BrO

MeO+

RT. 15 min.

SHSi

32

ISOLUTE® Si-ThiolMetal Scavenger

1.26 Pd(OAc)2 MeCN <1 <1 13% 0.29

mmol/g Pd Reagents Solvent

BatchRT. 2 h

Cartridge

% weight

mmol Scaven

ged

33



34

MP-TsO-TEMPOBound Oxidizing Agent

• MP-TsO-TEMPO is a bound oxoammonium sulfonate• Resin is a mixture of active oxoammonium and reduced

hydroxylammonium species

• AdvantageHighly controlled reaction. No over-oxidation to acid.Stable

• Applications Include:Oxidation of benzylic, allylic, acetylenic and cyclic secondary alcohols

NSO3 H

OH

O3SN O

MP-TsO-TEMPO(As provided)

35

MP-TsO-TEMPOOxidation of Alcohols

OHR

SO3 N+

OO

R

+- Solvent

Temp / Time

Alcohol Method Solvent Temp Time Yield

Non-μW

μW

Non-μW

μW

Non-μW

μW

Non-μW

μW

Non-μW

μW

CH3CN rt 16 h 95 %

DCM 100 oC 10 min 100 %

CH3CN rt 16 h 99 %

DCM 60 oC 2 h 100 %

CH3CN rt 16 h 70 %

DCM 60 oC 5 min 93%

DCM rt 16 h 70 %

DCM 60 oC 1.5 min 100 %

DCM rt 16 h 100 %

DCM 60 oC 2.5 min 100 %

O

OH

OH

Br

OH

OH

OH

OH

Lundin, R. Lundin, R. www.biotagepathfinder.comwww.biotagepathfinder.com

Si

36



37

Bound Reagents Reductive Amination

• Stable reagents on inert macroporous scaffold • Limited swelling• Very little pressure build up under acidic conditions• Masked toxicity • Easy to handle and work-up

NEt3 (CN)BH3

2-3 mmol/ g

NEt3 (OAc)3BH

2 mmol/ g

NEt3 BH4

3-3.2 mmol/ g

38

MP-CNBH3Reductive Amination

O

MeO

Amine Carbonyl Convn. Yield

μWYield

79 % 98 %

91 % 85 %

39 % 77 %

63 % 79 %

69 % 73 %

O

Me

NH

NNH2

R3

O

R2

ArNH

R R3

NR Ar

CNBH3

R2

+5-25% AcOH/DCM

2.5 eq

O

O

NH2

O

O

O

ONH

ON

NH2

Conventional condition:(1) THF(2) room temp, 16 h

PannagiotisPannagiotis, P. www. , P. www. biotagepathfinder.combiotagepathfinder.com

Microwave condition:(1) DCM(2) 110 oC, 5-7 min

•• DCM low boiling solvent, DCM low boiling solvent, selected for ease of workupselected for ease of workup

•• DMF & NMP alternate high boiling solventsDMF & NMP alternate high boiling solvents

39

ISOLUTE® Si-Tosyl Hydrazine

SiS

O

O

NHNH2

ISOLUTE Si-Ts-NHNH2

Si

• ISOLUTE Si-Tosyl Hydrazine is a silica supported equivalent of p-toluenesulfonyl hydrazine

• Applications Include:Scavenger of aldehydes and ketones

40

Removal of excess carbonyl from reductive amination reactions

OO

H

NH+

0.5 mmol0.7 mmol

THF, 5% HOAc

120 ºC6 min.

-TS-Hydrazine

600 mg N

OCH3-(AcO)3BHMP Si

41


• Amidation• Aryl-aryl bond formation (Suzuki Reaction)• Alkylation• Oxidation• Reductive amination• Acid catalyzed Reactions• Base Catalyzed reaction

42

SO O

OH

Bound Acid: MP-TsOHISOLUTE® Si-TsOH

• Bound sulfonic acid equivalent

S

O

O

O-Si

MP-TsOH ISOLUTE® Si-TsOH

Scavenger for amines & basic compoundsCatch and Release purifications

• Applications:Acid catalyst

Cleavage of acid sensitive groups eg BOC-

Si

43

O

CF3

OH

NH

NH2

N NCF3+ Acid

EtOH

Solid-supported TsOHMicrowave-assisted Pyrazole Synthesis

Entry Acid Method Temp time Yield

1 p-TsOH Non-μW

μW

Non-μW

μW

7 h 95 %

2 p-TsOH

100 oC

160 oC

100 oC

5 min 61 %

160 oC

3 6 h 84 %

4 5 min 95 %

SO3H

Si-TsOH

SO3H

Si-TsOH

Humphries, P. et al, Tetrahedron Lett, 2006 47, 2443-2446

44

Solid-supported TsOHMicrowave-Assisted Boc- Removal

SO O

NR 1

NR

R 3

H

90% 75%

91%

92%

89% 72%

61%

71%S

OO

NHN

N

SO

O

NHN

N

S

OO

NHN

S

OO

NH2N

N

SO

O

NH2N

SO

O

NH2NH SO

O

NH2N

CH3

S

OO

NH2N

H

NS

N

OO

BocR1

R

R3

TFA/ DCM

RT. Overnight

100 °C 5 min

Yun-Shan Liu, Cunxiang Zhao, David E. Bergbreiter, Daniel Romo, J. Org. Chem 1998, 63, 3471-3473

Shahnaz Ghassemi, Kristin Fuchs, Molecular Diversity 2005, vol.9, 4

SO

OHO

Si

45



46


NH

HN

NH2Si


• ISOLUTE Si-Triamine is a silica supported equivalent of Diethylenetriamino

• Applications Include:Electrophile scavenger (for aldehydes, acid chlorides, sulfonyl chlorides and isothiocyanates)Heavy metal ions scavenger such as Mn2+, Fe3+, Co2+, Ni2+, Cu2+,

Pb2+, Ru2+ and Zn2+

47

De-blocking of Base Sensitive Protecting Group By Solid Bonded Base

S OO O O

NR

R1S

O O

B

SO O

B+ NH

R1

R

Base

1,1-dioxobenzo[b]thiophene-2-ylmethyloxycarbonyl (Bsmoc-) is a base sensitive amino protecting group used commonly in peptide synthesis

Bsmoc-

48

μW 100 ºC, 4 min

0 .0 0

0 .2 0

0 .4 0

0 .6 0

0 .8 0

1 .0 0

1 .2 0

1 .4 0

2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 00 1 4 0 0 1 6 0 0

8.96

7

0 . 0 0

0 . 0 5

0 . 1 0

0 . 1 5

0 . 2 0

2 . 0 0 4 . 0 0 6 . 0 0 8 . 0 0 1 0 . 0 0 1 2 . 0 0 1 4 . 0 0 1 6 . 0 0

2.83

8

7.60

2

0 .0 0

0 .1 0

0 .2 0

0 .3 0

0 .4 0

0 .5 0

2 .0 0 4 .0 0 6 .0 0 8 .0 0 1 0 .0 0 1 2 .0 0 1 4 .0 0 1 6 .00

2.83

9

8.48

7RT 1 h

NH2 Cl

A

A

ISOLUTE® Si-TriamineBSMOC-group Cleavage

μW 100 ºC, 4 min.

-TriamineSi

NH2 ClS OO O

O

NH Cl

49

HATU

NHNH

NH2Si

NHO

O

H-Try(t-Bu)NH

NHNH2Si

NiPr

iPrPS

N=C=NPS

S OO O

O

NH

OHO

+

BSMOCNH

O

O

µW 90 ºc, 6 min.ACN

DMAP, DCM

OH

O

NH2 O

µW 100 ºC 5 min.

µW 90 ºc, 6 min.ACN

Rapid Multi-step Solution Phase Synthesis

TLC plate monitoring, reaction progress.

Free amine Nin (+)

Bsmoc-Tyr(t-Bu)-Gly-ODCP

H-Tyr(t-Bu)-Gly-ODCP

μW100 oC, 5 min

BSMOC-Tyr-OH

H-Tyr(t-Bu)

NHO

O

Bsmoc-Try(t-Bu)Bsmoc-Tyr(t-Bu)

50

SO

O O

O

NHCl

NHO

OBsmoc

OBsmoc-Try(t-Bu)-Gly

Bsmoc-Try(t-Bu) NH

OBsmoc-Phe-Val

Bsmoc-Val-Gly-Gly-O

ON

O

Bsmoc-Phe

NH2 Cl

NH2 O

O

OH-Try(t-Bu)-Gly

H-Try(t-Bu) NH

OH-Phe-Val

H-Val-Gly-Gly-O

ON

O

HPhe

Isolated Yield

MS M+1

95 %

91 %

90 %

89%

94%

87%

87%

128.1

170.1

389.3

319.2

355.1

260.1

293.1

SO

O O

O

NHCl

NHO

OBsmoc

OBsmoc-Try(t-Bu)-Gly

Bsmoc-Try(t-Bu) NH

OBsmoc-Phe-Val

Bsmoc-Val-Gly-Gly-O

ON

O

Bsmoc-Phe

NH2 Cl

NH2 O

O

OH-Try(t-Bu)-Gly

H-Try(t-Bu) NH

OH-Phe-Val

H-Val-Gly-Gly-O

ON

O

HPhe

Isolated Yield

MS M+1

95 %

91 %

90 %

89%

94%

87%

87%

128.1

170.1

389.3

319.2

355.1

260.1

293.1

Bsmoc-Amine Amine

Reaction Scope (Examples)

51

ISOLUTE® Si-Triaminemetal scavenger

Pd(OAc)2 MeCN <1 <1 11%

(Ph3P)2PdCl2 DMF/THF (1:1) <1 <1 12%Si-Triamine 2.2

54.6 mg, 0.24 mmol of Pd(OAC)2was scavenged,11% by weight of Si-triamine

59.4 mg, 0.09 mmol of (Ph3P)2PdCl2 was scavenged,12% by weight of Si-triamine

52

SUMMARY

• MAOS continues to be a versatile tool for accelerating synthesis

• Solid bonded Reagents and Scavengers can help in significantly reducing the work-up and purification bottleneck

• Combining MAOS with Solid bonded Reagents and Scavengerscan accelerate total compound production time

Thank You for Your Attention!

Dr. Farah Mavandadi

rapid compound production -...

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