The reaction of thio acids with azides: a new mechanism and new synthetic applications.

A new amide synthesis strategy based on a fundamental mechanistic revision of the reaction of thio acids and organic azides is presented. The data demonstrate that amines are not formed as intermediates in this reaction. Alternative mechanisms proceeding through a thiatriazoline intermediate are suggested. The reaction has been applied to the preparation of simple and architecturally complex amides that are difficult to access using conventional methods. The reaction is chemoselective, effective for unprotected substrates, and compatible with aprotic and protic solvents, including water.