Copper-catalyzed highly efficient multicomponent reactions: synthesis of 2-(sulfonylimino)-4-(alkylimino)azetidine derivatives.

[reaction: see text] Under very mild conditions, functionalized 2-(sulfonylimino)-4-(alkylimino)azetidine derivatives were prepared in good to excellent yields via a copper-catalyzed multicomponent reaction of readily available terminal alkynes, sulfonyl azides, and carbodiimides without the assistance of a base. The mechanism may be through a [2 + 2] cycloaddition.