A general synthesis of azetidines by copper-catalysed photoinduced anti-Baldwin radical cyclization of ynamides

A general anti-Baldwin radical 4-exo-dig cyclization from nitrogen-substituted alkynes is reported. Upon reaction with a heteroleptic copper complex in the presence of an amine and under visible light irradiation, a range of ynamides were shown to smoothly cyclize to the corresponding azetidines, useful building blocks in natural product synthesis and medicinal chemistry, with full control of the regioselectivity of the cyclization resulting from a unique and underrated radical 4-exo-dig pathway.

Automated summary

This study reports a general anti-Baldwin radical 4-exo-dig cyclization from nitrogen-substituted alkynes. Under visible light irradiation in the presence of a heteroleptic copper complex and an amine, a range of ynamides smoothly cyclize to the corresponding azetidines. The cyclization reaction shows full control of the regioselectivity, allowing the synthesis of useful building blocks in natural product synthesis and medicinal chemistry.