One-Pot Synthesis of Polysubstituted 3-Amino-2-oxo-2,7-dihydro-1H-azepines

Abstract

A facile and efficient synthesis of novel seven-membered heterocyclic derivatives containing 3-aminoazepan-2-one backbone is described using 1,4-protected piperazine-2,5-diones and alkynes as starting materials. The reaction may undergo Michael­ addition, unusual nucleophilic attack to an amide group, and keto–enol tautomerization. The reaction showed different reactivity when using substrates with different protecting groups: it had higher efficiency when using either alkanoyl-protecting group with cesium carbonate as the base, or benzoyl-protecting group with triethylamine as the base, but no reaction when using benzyl or allyl protecting groups with a variety of bases (Et₃N, DBU, K₂CO₃, Cs₂CO₃, KHCO₃, CsHCO₃, and KO<i>t</i>-Bu).