Construction of pyrazolo[3,4-b]pyridines and pyrazolo[4,3-c]pyridines by ring closure of 3-acylpyridine N-oxide tosylhydrazones.

Tetrahedron Letters
William J LominacJames M Hanna

Abstract

3-Acylpyridine N-oxide tosylhydrazones give good overall yields of a mixture of pyrazolo[3,4-b]pyridines and pyrazolo[4,3-c]pyridines when treated with an electrophilic additive and an amine base. (Z)-Hydrazones cyclize readily, while (E)-hydrazones fail to react under the reported conditions. The reaction takes place at room temperature, and moderate regiocontrol over the cyclization can be achieved by varying the electrophile/solvent combination.

Citations

Oct 30, 2016·Organic & Biomolecular Chemistry·Song Thi LeNagatoshi Nishiwaki
Aug 28, 2014·Beilstein Journal of Organic Chemistry·Barbara PalkaWolfgang Holzer
Aug 14, 2020·Organic & Biomolecular Chemistry·Balakrishna AegurlaRama Krishna Peddinti
May 26, 2017·The Journal of Organic Chemistry·Sina P ZuckerC Christoph Tzschucke

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