Synthesis and 1,3-dipolar cycloaddition reactions of N-aryl-C,C-dimethoxycarbonylnitrones

Arylnitroso compounds 1-3 easily reacted with dimethyl bromomalonate to give the corresponding N-aryl-C,C-dimethoxycarbonylnitrones (4-6). Treatment of CC-dimethoxycarbonyl-N-(1-naphthyl)nitrone (4) with acetylene compounds (dimethyl acetylenedicarboxylate, methyl 2-butynoate or ethyl phenylpropiolate) caused 1,3-dipolar cycloaddition to furnish the corresponding 1H-benz[g]indolines (7a-c). In a similar manner, the reactions of nitrones 5 and 6 with acetylene compounds afforded the corresponding indolines 9a-c and 11a-c together with 4-oxazolines 13a-c and 14a-c.