Cu(I)-catalyzed tandem benzyldiazoester coupling with terminal alkyne-allene formation-Michael reaction: application to the syntheses of oxa and azacycles.

A simple and practical procedure for the synthesis of aza- and oxacycles, which possess an array of stereogenic functionalities, is described. This protocol relies on tandem Cu-catalyzed coupling of suitably functionalized terminal alkyne with diazoester followed by isomerization and subsequent aza or oxa-Michael reaction, thus generating the required scaffold with high diastereoselectivity.