Base-Controlled Synthesis of Heteroatom-Embedded 9-Membered Cycloalkynes and 6-Membered Sultams through Copper-Catalyzed Cyclization

Abstract

A facile copper-catalyzed, base-controlled cyclization reaction has been developed for the synthesis of 9-membered cycloalkyne and 6-membered heterocycle sultams under mild conditions. This protocol utilizes a copper-catalyzed intramolecular A³ (alkyne–aldehyde–amine) coupling reaction to efficiently synthesize 9-membered cycloalkyne sultams in yields up to 90%. Alternatively, by substituting NaHCO₃ with DBU, the protocol achieves selective deprotection of the N-propargyl group, thereby facilitating the formation of 6-membered heterocyclic sultams, also in high yields.