Seven and more membered cyclic anhydrides in the Castagnoli-Cushman Reaction

The possibility of utilizing seven-, eight- and nine-membered cyclic anhydrides in the Castagnoli-Cushman reaction is investigated. The prospects to employ other cyclic anhydrides containing more methylene groups are also shown. The structures of unexpected products, four-membered lactams, obtained, as well as other side products, are determined and proven. The reasons for the formation of such products are discussed. The described results are significant for further investigation and understanding of the mechanism of the Castagnoli-Cushman reaction depending on the structures of starting substrates. The elaborated methodology can also be used for the synthesis of such a rare class of lactams functionalized by the carboxylic group.