Synthesis of 5-alkyl-5-aryl-γ-lactams from 1-aryl-substituted nitroalkanes and methyl acrylate via Michael addition and reductive lactamization

A general method for accessing 5-alkyl-5-aryl-γ-lactams has been developed using readily available aryl bromides, nitroalkanes, and methyl acrylate as the starting materials. The palladium-catalyzed arylation of nitroalkanes gave the 1-aryl-substituted nitroalkanes, which underwent the DBU-mediated Michael addition with methyl acrylate at room temperature to afford the methyl 4-aryl-4-nitroalkanoates. The latter were then subjected to the nitro reduction using NaBH4-NiCl2·6H2O in MeOH at 0 °C to furnish, after treatment with aqueous K2CO3 at room temperature, the 5-alkyl-5-aryl-γ-lactams in good to excellent overall yields. Selected examples of N-alkylation of the γ-lactams were also illustrated.