

SYNTHESIS OF METHYL(ETHYL) PYRAZOLO[4,3-b]PYRIDINE-6-CARBOXYLATES AND THEIR CONVERSION TO tert-BUTYL 4,5,6,7-TETRAHYDROPYRAZOLO-[4,3-b]PYRIDINE-6-CARBOXYLATES

Abstract
N-Boc-4-aminopyrazole-5-carbaldehydes react with methyl 3,3-dimethoxypropanoate or β-keto esters in acetic acid under reflux to form methyl(ethyl) pyrazolo[4,3-b]pyridine-6-carboxylates, which were converted to the corresponding tert-butyl carboxylates via intermediate carboxylic acids. Their subsequent hydrogenation on a 10% Pd/C catalyst at 100°C and 25 atm afforded tert-butyl 4,5,6,7-tetrahydropyrazolo[4,3-b]pyridine-6-carboxylates.
Keywords
alkyl pyrazolo[4,3-b]pyridine-6-carboxylates; N-Boc-4-aminopyrazole-5-carbaldehydes; 3,3-dimethoxypropionate; β-keto esters; tetrahydropyrazolo[4,3-b]pyridine-6-carboxylates; Pd/C catalytic hydrogenation.
Latvian Institute of Organic Synthesis - Aizkraukles iela, 21, Riga, LV-1006, Latvia - hgs@osi.lv