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.

Palladium-Catalyzed Highly Regio-and Stereoselective Synthesis of 4-Alkylidene-4H-3,1-benzoxazines from N-Acyl-o-alkynylanilines. -A new, straightforward, and highly selective method to prepare 4-alkylidenebenzoxazines of type (II) and (IV) is reported. -(SAITO*, T.; OGAWA, S.; TAKEI, N.; KUTSUMURA, N.; OTANI, T.; Org. Lett. 13 (2011) 5, 1098-1101, http://dx.doi.org/10.1021/ol103130s ; Dep. Chem., Fac. Sci., Sci. Univ. Tokyo, Shinjuku, Tokyo 162, Japan; Eng.) -Jannicke 23-158