Palladium-Catalyzed Highly Regio- and Stereoselective Synthesis of 4-Alkylidene-4H-3,1-benzoxazines from N-Acyl-o-alkynylanilines

The highly regio- and stereoselective 6-exo-dig mode cyclization of N-acyl-o-alkynylanilines producing 4-alkylidene-3,1-benzoxazines occurred unpredictably by use of a proper catalyst [Pd(OAc)(2)] and an effective additive (acetic acid) under suitable reaction conditions.