Parallel synthesis of a multi-substituted benzo[b]furan library

The solution-phase parallel synthesis of a 121-member library of multi-substituted benzo b]furans is described. 2,3,5-Trisubstituted benzo b]furans have been prepared by the palladium-catalyzed substitution of 3-iodobenzofurans by Suzuki-Miyaura, carbonylative Suzuki, Sonogashira, Heck, and carboalkoxylation chemistry. The 3-iodobenzofurans are readily prepared in good to excellent yields by the palladium/copper-catalyzed cross-coupling of various o-iodoanisoles and terminal alkynes, followed by electrophilic cyclization with ICl.