Zn(II)-Catalyzed One-Pot Synthesis of Coumarins from Ynamides and Salicylaldehydes.

A highly efficient and straightforward synthesis of diversely substituted coumarins from ynamides and salicylaldehydes in the presence of Zn(II) catalyst has been developed. The sulfonamide moiety of ynamides was successfully recycled in this process, serving as an effective traceless directing group for high regioselectivity in the bond-forming event. The advantages of this protocol are good functional group tolerance, broad substrate scope, simple and high-yielding reaction, recovery/reuse of the sulfonamides, low catalyst loading of inexpensive catalyst, and, by these merits, a more cost-effective and greener process.