Keten. Part XIV. Adducts of diphenylketen with aza-arenes

Abstract

The cycloadducts of diphenylketen with quinoline, isoquinoline, 3-methylisoquinoline, phenanthridine, benzoxazole, 5-methylbenzoxazole, 6-methylbenzoxazole, and benzothiazole are assigned the oxazinone part-structure (3b). These adducts react with nucleophiles in two ways. Benzylamine attacks the oxazinone ring directly in some cases, whereas aniline only reacts after dissociation of the adduct to form free diphenylketen. Addition of diphenylketen to benzimidazoles gives two types of adduct. Oxazinones (5) are formed by benzimidazoles with electronegative substituents at position 1, whereas 1-methyl-, 1-benzyl-, and 1-phenyl-benzimidazoles form 1,2-disubstituted benzimidazoles (14). 1-Methylimidazole behaves similarly, giving the 1,2-disubstituted imidazole (15). The benzothiazole adduct (5c) is isomerised to the other type of adduct (14d) on heating in acetonitrile.