Heterocycles by cycloaddition. Part I. Cycloaddition–extrusion–ring expansion reactions of five-membered mesoionic compounds with diphenylcyclopropenone and related compounds: preparation of six-membered heterocycles

Abstract

Cycloaddition–extrusion–ring expansion reactions of mesoionic oxazolones (9) and a thiazolone (15) with 2,3-diphenylcyclopropenylidene compounds (10) gave pyridin-4-one, -thione, and -imine, and 4-methylene-dihydropyridine derivatives (12). The reactions of a mesoionic dithiolone (17) with cyclopropenylidene derivatives mainly gave thiopyranone and 4-methylenethiopyran derivatives (19).