Regio- and Stereoselective Addition of Brønsted Acids to Yndiamides: Synthesis of N,O,N- and N,S,N-Trisubstituted Ketene Acetals

Abstract Yndiamides, N,N-disubstituted alkynes, are versatile building blocks for the synthesis of nitrogen-containing organic molecules. Unlike ynamides, relatives that inherently polarized by a single nitrogen substituent, their pseudo-symmetric nature renders regioselective reactions challenging. Here we report investigations into regio­selective addition Brønsted acids to non-symmetric yndiamides, reaction delivers N,O,N- and N,S,N-trisubstituted ketene acetals with excellent regio- stereoselectivity.