Divergent Synthesis of Pyrazolo[1,5- a]pyridines and Imidazo[1,5- a]pyridines via Reagent-Controlled Cleavage of the C-N or C-C Azirine Bond in 2-Pyridylazirines

Anastasiya V Agafonova; Artem A Golubev; Ilia A Smetanin; Alexander F Khlebnikov; Dar'ya V Spiridonova; Mikhail S Novikov

doi:10.1021/acs.orglett.3c02696

Divergent Synthesis of Pyrazolo[1,5- a]pyridines and Imidazo[1,5- a]pyridines via Reagent-Controlled Cleavage of the C-N or C-C Azirine Bond in 2-Pyridylazirines

Org Lett. 2023 Oct 6;25(39):7165-7169. doi: 10.1021/acs.orglett.3c02696. Epub 2023 Sep 22.

Authors

Anastasiya V Agafonova¹, Artem A Golubev¹, Ilia A Smetanin¹, Alexander F Khlebnikov¹, Dar'ya V Spiridonova¹, Mikhail S Novikov¹

Affiliation

¹ Institute of Chemistry, St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.

PMID: 37738046
DOI: 10.1021/acs.orglett.3c02696

Abstract

The three-membered ring in 2-(2-pyridyl)azirine-2-carboxylic esters and thioesters can undergo selective cleavage of either the N-C2 bond under copper(II) catalysis or the C-C bond under the action of HCl to provide isomeric azirine ring expansion products of pyrazolo[1,5-a]pyridine or imidazo[1,5-a]pyridine series, respectively. Mild catalytic reaction conditions for the formation of pyrazolopyridines make it possible to obtain them directly from 4-bromoisoxazoles by a one-pot, three-stage procedure without isolating the intermediate 2-bromoazirines and 2-(2-pyridyl)azirines.