Beilstein J. Org. Chem.2016,12, 2503–2510, doi:10.3762/bjoc.12.245
; Chichibabin synthesis; indolizine; pyridiniumN-ylide; sydnone; Introduction
In recent decades, interest in the syntheses of biheteroaryls has been focused on the creation of new hetaryl–hetaryl C(sp2)–C(sp2) bonds, in particular through cross-coupling reactions. These reactions are catalyzed by palladium or
products 12a–c with yields in the range of 41–52%.
Bearing in mind that the formation of indolizines through Chichibabin synthesis and 1,3-dipolar cycloaddition reaction requires in both cases the formation of an intermediate pyridiniumN-ylide, it is expected that in these cycloadditions a mixture of