Sequential Silylcarbocyclization/Silicon-Based Cross-Coupling Reactions

Abstract

A sequential rhodium-catalyzed silylcarbocyclization of enynes parlayed with a palladium-catalyzed, silicon-based cross-coupling reaction has been developed for the synthesis of highly substituted cyclopentanes. 1,6-Enynes reacted with benzyldimethylsilane in the presence of rhodium catalysts to afford five-membered rings bearing a (Z)-alkylidenylbenzylsilyl group. A variety of substitution patterns and heteroatom substituents were compatible. The silylcarbocyclization in which an unsaturated ester participated was also achieved. The resulting alkylidenylsilanes underwent palladium-catalyzed cross-coupling using tetra-n-butylammonium fluoride. This cross-coupling reaction displayed a broad substrate scope. A wide variety of substitution patterns, electronic properties, and heteroatoms were compatible. All of the cross-coupling reactions proceeded in high yields under very mild conditions and with complete retention of double bond configuration, resulting in densely functionalized 3-(Z)-benzylidenecyclopentanes and heterocycles.