Palladium-Pincer-Complex-Catalyzed Transformations Involving ­Organometallic Species

Abstract

Highly selective palladium-catalyzed transformations involving organoboranes, silanes, stannanes and selenides were developed by employment of pincer-complex catalysts. A novel catalytic transformation was designed for allylation of aldehyde and imine electrophiles using allylstannanes and allylboranes. These reactions proceed under mild and neutral conditions to afford homo­allyl alcohols and amines with a high level of functional group tolerance. The regio- and stereoselectivity of the transformations is very high, and promising levels of enantioselectivity could be obtained by application of chiral pincer complexes. The rest of the presented reactions involve synthesis of allylstannanes, allylboranes, allenyl stannanes/silanes and organoselenides using various di­metallic reagents. Most of the presented pincer-complex-catalyzed reactions are not amenable with traditional palladium(0) catalysis. The employed mild and neutral reaction conditions allow the iso­lation of stereo- and regiodefined organometallic species, which are useful building blocks in advanced organic synthesis and in natural product synthesis. The mechanistic studies have revealed some ­important differences between the mechanism of pincer-complex-catalyzed and palladium(0)-catalyzed processes.