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

Yakovenko, Georgiy G.; Saliyeva, Lesya; Русанов, Эдуард Б.; Donchak, Il’ya S.; Вовк, М. В.

doi:10.1007/s10593-021-03032-z

Cited by 2 publications

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“… Methods for the synthesis of pyrazolo [4,3- b ]pyridines: ( A ) annulation of a pyridine fragment to an amino substituted pyrazole ring [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ]; ( B ) annulation of a pyrazole ring to functionalized pyridine core [ 22 ]; ( C ) synthesis from available 3-nitropyridines. …”

Section: Figures and Schemesmentioning

confidence: 99%

“…Methods for the synthesis of pyrazolo [4,3- b ]pyridines are usually based on the annulation of a pyridine fragment to an amino-substituted pyrazole ring, Scheme 1 A. Two main approaches include cyclocondensation of unstable 4-aminopyrazole-5-carbaldehydes in their N-protected forms [ 14 , 15 , 16 ], as well as cyclization of 5-functionalized 4-aminopyrazoles [ 17 ]. Another example deals with cyclization of 4-amino-5-(indol-3-yl)pyrazole with aldehydes [ 18 , 19 ] or sodium nitromalonodialdehyde [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

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Straightforward and Efficient Protocol for the Synthesis of Pyrazolo [4,3-b]pyridines and Indazoles

Nikol’skiy

Minyaev

Bastrakov

et al. 2023

IJMS

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An efficient method for the synthesis of pyrazolo [4,3-b]pyridines has been developed on the basis of readily available 2-chloro-3-nitropyridines via a sequence of SNAr and modified Japp–Klingemann reactions. The method offers a number of advantages including utilization of stable arenediazonium tosylates, operational simplicity as well as combining the azo-coupling, deacylation and pyrazole ring annulation steps in a one-pot manner. An unusual rearrangement (C-N-migration of the acetyl group) was observed and a plausible mechanism was proposed based on the isolated intermediates and NMR experiments. In addition, the developed protocol was successfully applied to the synthesis of 1-arylindazoles combining the Japp–Klingemann reaction and cyclization of the resulting hydrazone as a one-pot procedure.

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