Microwave-Assisted Chemistry– from HTS to CD

Jane Buus Laursen, PhDLead Generation

AstraZeneca R&D Mölndal

Outline

• Microwave infrastructure in Mölndal• Microwave-assisted chemistry in large

library synthesis• Microwave-assisted chemistry in lead

generation• Microwave-assisted chemistry in lead

optimisation

• 10 instruments, 9 of these have queue systems

– 4 Initiators (0.2-20mL)

– 1 Synthesizer (liquid handling, 0.2-20mL)

– 2 Creators (0.2-20mL)

– 3 Optimizers (0.2-20mL or 0.2-5mL)

• Open access

– Available locally to ~120 bench chemists

– Used regularly by >80% of these

Microwave equipment in Mölndal

• Knowledge Management– Electronic lab journal feeds

information to in-house reaction database

– Microwave-assisted reactions are searchable if “microwave reagent” is specified

• Usage– ~10% of all unique

reactions are done using microwave heating

Knowledge Management & Usage

Impact on cycle times

• Faster optimisation of reaction conditions– Quick failures

• Faster compound production– More time for evaluation and design

– Faster access to results leading to faster decision making

• Compound synthesis is no longer the bottle neck in lead generation thanks to microwave, parallel synthesis and purification techniques

CCE* library synthesis

• Acylated amino-phthalimides• 480-member library in a 20 x 24 matrix• Single compound scale: 200µmol• 3 synthetic steps (first step microwave-assisted)

O

O

N R1

NHX

R2

X = CO, SO2

*: Compound Collection Enhancement

J. Sundell & J.B. Laursen

Optimising reaction conditions

• Step 1: 1 eq R1-NH2, AcOH, e.g. an optionally substituted benzyl amine:

• Step 2: 0.1 eq Pd/C, H2 (1 atm), EtOAc/MeOH/AcOH (3:1:1), 3h, rt• Step 3: 2.5 eq R2XCl (X = CO, SO2), pyridine, 70°C, 16h or µW

O

O

O

N+ OO

O

O

N R1

NH2 O

O

N

NHX

R2

R1

O

O

N

N+ OO

R1

Step 1

X = CO, SO2

Step 3Step 2

~90% conversion7h70°C~95% conversion30min115°C

~30% conversion30h20°C

>95% conversion5minµW 170°C

ConversionTimeTemperature

J. Sundell & J.B. Laursen

Technical solution

• 480-member library in a 20 x 24 matrix

• Synthetic scale & equipment:

– Step 1: 5mmol (2×20mL microwave vials per reaction)

– Step 2: 5mmol (Radley carousel, 50mL flasks)

– Step 3: 200µmol (Bohdan MiniBlockTM, 4mL reaction tubes)

O

O

O

N+ OO

O

O

N R1

NH2 O

O

N

NHX

R2

R1

O

O

N

N+ OO

R1

Step 1

X = CO, SO2

Step 3Step 2

Microwave

×20 ×480×20

J. Sundell & J.B. Laursen

Lead generation library synthesis

• Imidazopyridines• 288-member library in a 6 x 48 matrix• Single compound scale: 200µmol

N

NNH2

R2

R1

E. Wellner

Synthetic route

N

NH2

R1 N+

NH2

O

Cl

Cl

R1 ClN

NO

HR1

N

NO

H

R2

R1N

NNH2

H

R2

R1

2 step one-potMicrowave-assisted

2 step one-potMicrowave-assisted

• 7 synthetic steps• 4 of these microwave-assisted

E. Wellner

Synthesis of imidazopyridinealdehydes

• Formation of the pyridinium salt limited by the nature of R1

• Cyclisation: Mixture of dichloride and acetal not separated

N

NH2

R1

O

Cl

ClCl

N+

NH2

O

Cl

Cl

R1 Cl

N

NCl

ClR1

N

NO

O

Et

Et

R1

N

NO

HR1

DME, RT

EtOHµW 120°C2000s

quant.

0.6 M HCl aqµW 120°C, 500s

90%

E. Wellner

Reductive amination

• Catalytic pivalic acid was used instead of HOAc to avoid acylation of the product.

• Hydrolytic conditions involve water/pivalic acid

N

NO

H

R2

R1

NH2

O O

N

NNH

H

O

O

R2

R1PS-NEt3CNBH3

N

NNH2

H

R2

R1EtOH/pivalic acid

µW 140°C, 1400s

not isolated

water/EtOH(37% pivalic acid)

µW 120°C, 540s

E. Wellner

N

NH2

R1N

+

NH2

O

Cl

Cl

R1 ClN

NO

HR1

N

NO

H

R2

R1

N

NO

O

Et

Et

R1

N

NNH2

H

R2

R1

Step 1 Step 2 Step 3

Step 4Step 5

Step 6Step 7

Microwave Microwave

Microwave

Practical solution

• 288-member library in a 6 x 48 matrix

• Synthetic scale & equipment:

– Step 1-4: 10mmol (conventional flasks, 20mL microwave vials)

– Step 5: 200µmol (Bohdan MiniBlockTM, 2mL)

– Step 6-7: 200µmol (1mL microwave vials, Synthesizer liquid handling)

×6

×288

×6 ×6

×288

E. Wellner

Notes on microwave-assisted MPS

+ Fast reaction times+ Walk-away time in library synthesis+ Can be combined with liquid handling robotics

– Capacity in queue system– Limitation in scale (< 10 mmol)– Post-synthetic handling

e.g. filtration, SPE, phase separators

– Capping / de-capping– Plate format (not 96-well)

Lead optimisation synthesis

N

N

N

OHO

O

• New pyrazinone shows to be less reactive• Calculation of activation energy to aid optimisation of

reaction conditions

U. Fahlander et al.Work presented in part at the 232nd ACS National Meeting, San Francisco, US, Sept. 10-14, 2006, MEDI 392.

Synthetic route

N

N

Cl

Cl

NH

OO

N

N

N

OO

Cl

N

N

N

OO

O

N

N

N

OHO

O

NH

N

N

OO

O

N O

O

+

EtOH / water 3:11.5 eq NEt3

µW 170°C, 20 min (80%)

reflux over night (72%)

2 eq. KOAcHOAc / water 7:1

reflux 5 h (92%)

µW 150°C, 10 min (87%)

4 eq. DMF

µW 150°C, 20min (90%)

reflux 3 h, thenr.t over night (68%)

5 eq. LiOH

reflux 90 min (66%)

• The obvious route:

• Alternative route:

N

N

O

Cl

NH

RNN

NO R

N

N

Cl

Cl

NH

RNN

NCl R

+

+µW 170°C, 20 min (80%)

reflux over night (72%)

µW 170°C, 20 min (0%)

U. Fahlander

Reaction rate

23.910 h

19.736 sec

21.10.1 h

22.51 h

∆G* (kcal/mol)t½

1.4 kcal/mol decrease in activation energy = 10 × reaction rate

10°C increased reaction temperature = 2 × reaction rate

A. Broo

K = ν exp(-∆G*/RT) t½= ln2/Kν = KbT/h ≈ 6.2*1012

Calculation of activation energy

• Can calculations explain the reactivity difference?

Activation energy (∆E‡) of SNAr reaction:

Ar

X

NH

N

Ar

23.03

17.77

21.64

23.3727.6122.8727.6822.0723.34Br

21.4726.7931.6926.0027.39Cl

Ar

N

N

O

X

N

N

OH

X

N

N

O

X

N

N

OH

X

N

N

O

Br

N

NH

O

Br

N

N

X

X

N

Cl

Cl

N

N

Cl

Cl

A. Broo

N

N

O

Cl

NH

R

N

N

N

O

R

+µW 170°C, 20 min (0%)

Calculations vs. results

NH

R

N

N

N

Cl

R

N

N

Cl

Cl

+µW 150°C, 20 min

62%

∆E‡ = 21.5 kcal/mol

∆E‡ = 27.4 kcal/mol

U. Fahlander & A. Broo

µW ~185°C (20 bar), 22h

69%

Results

N

N

Cl

ONH

OHO

N

N

N

OHO

O

+

µW 180°C (20 bar) 20 h (90%)

5 equiv. NEt3Ethanol / water 3:1

• The 4 step approach could be replaced by a microwave assisted 1-step synthesis:

U. Fahlander

”A good drug is hard to find-A perfect one takes longer”

ACS meeting, New Orleans, 1999

”A good drug is hard to find-A perfect one takes longer”

can be done!”AstraZeneca R&D Mölndal

Acknowledgements

• Colleagues at AstraZeneca Mölndal– Johan Sundell (CCE)

– Eric Wellner (Lead Generation)

– Ulf Fahlander (Lead Optimisation)

– Anders Broo (Computational Chemistry)

– Fritiof Pontén (Up-scaling lab)

– Niklas Falk (ChemInformatics)