Platinum Metals Rev., 2001, 45, (4), 163
Microwave-Assisted Homogeneous Sonogashira Coupling Reactions
Arylalkynes are intermediates for the synthesis of a variety of compounds: heterocycles, cyclophanes, enediyne antibiotics, etc. Sonogashira coupling has provided these compounds via the palladium(O)-catalysed coupling of terminal alkynes and aryl iodides in the presence of copper(I) and a base. Weaknesses of this reaction include long reaction times and the limited choice of reaction medium.
In recent years, microwave heating has emerged as a technique to speed up organic reactions. Now, a microwave-enhanced, rapid and efficient homogeneous-phase version of the Sonogashira coupling reaction of aryl iodides, bromides, triflates and an aryl chloride with trimethysilylacetylene has been established by scientists from Sweden (M. Erdélyi and A. Gogoll, J. Org. Chem ., 2001, 66, (12), 4165-4169). Pd(PPh3)2Cl2 and copper(I) iodide were used as the catalyst system, in the presence of diethylamine. Excellent yields (80 to 95%) were obtained in 5 to 25 minutes.