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.
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Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2021, 57(11), 1137–1145
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Yakovenko, G.G., Saliyeva, L.N., Rusanov, E.B. et al. 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. Chem Heterocycl Comp 57, 1137–1145 (2021). https://doi.org/10.1007/s10593-021-03032-z
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DOI: https://doi.org/10.1007/s10593-021-03032-z