Percarboxylic Acid Oxidation of α-Hydroxy-Substituted Alkoxy­allenes: The Unexpected Formation of Acyloxy-Substituted 1,2-Diketones and the Synthesis of Functionalized Quinoxalines

Treatment of α-hydroxy-substituted methoxyallene derivatives with meta -chloroperbenzoic acid provided acyloxy-substituted 1,2-diketones in moderate yields. A mechanism for the formation of these unexpected products is proposed. The configuration of the enantiopure compound ( S )-1-(3-methylquinoxalin-2-yl)-1-(4-nitrobenzoyl­oxy)propan-2-yl 3-chlorobenzoate – determined by X-ray crystal structure analysis – indicates the intermediacy of a carbenium ion during formation of the 1,2-diketones. The functionalized 1,2-diketones are valuable starting materials for a variety of products as demonstrated by the synthesis of quinoxalines, an imidazole derivative, and electron-deficient­ alkenes.