Agafonova AV, Golubev AA, Smetanin IA, Khlebnikov AF, Spiridonova DV, Novikov MS. 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;
25:7165-7169. [PMID:
37738046 DOI:
10.1021/acs.orglett.3c02696]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/23/2023]
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.
Collapse