Cycloaddition of unactivated 2-aza-1,3-dienes with heterocumulenes: a convenient route to the synthesis of 1,3-difunctionalized compounds

Abstract

The cycloaddition of unactivated 2-aza-1,3-dienes (2) with isocyanates and isothiocyanates (3) gives with complete regio- and chemo-selectivity 1,2-dihydropyrimidin-4(3H)-ones and -thiones (4). This is the first example of a cycloaddition of unactivated 2-aza-1,3-dienes with heterocumulenes. Enamino amides and thioamides (5) were obtained by reduction with LiAIH₄of (4). Also, 3-oxoamides and 3-oxothioamides (6) were prepared by acid hydrolysis of compound (4) or (5).