Palladium-Catalyzed Carbonylative Annulation of Internal Alkynes: Synthesis of 3,4-Disubstituted Coumarins
作者:Dmitry V. Kadnikov、Richard C. Larock
DOI:10.1021/jo0350763
日期:2003.11.1
The palladium-catalyzedannulation of internalalkynes by o-iodophenols in the presence of CO results in exclusive formation of coumarins. No isomeric chromones have been observed. The best reaction conditions utilize the 2-iodophenol, 5 equiv of alkyne, 1 atm of CO, 5 mol % Pd(OAc)2, 2 equiv of pyridine, and 1 equiv of n-Bu4NCl in DMF at 120 degrees C. The use of a sterically unhindered pyridine base