Stereocontrolled Formation of Several Carbon-Carbon Bonds in Acyclic Systems

Brook rearrangement represents a powerful approach to diastereoselectively prepare organometallic species using either the chirality of the substrates or the reagents. Following the subsequent Brook rearrangement, a new organolithium species is generated that reacts with various electrophiles to give the corresponding silyl benzyl ether in excellent yields and good diastereoselectivity. The conjugate addition of radical species to Michael acceptors leads to the formation of new radical species. The introduction of an alkyl radical trapping reagent then allows the formation of the second carbon-carbon bond. From the Brook and Wittig rearrangements, Michael addition, and carbometalation reaction to zinc and boron homologation reactions, the ability to design specific reactive intermediates for a given transformation represents a powerful solution to create more than one carbon-carbon bond per chemical step. Finally, in the days of asymmetric catalysis, the rare examples of catalytic asymmetric formation of several C-C bonds in acyclic systems clearly indicate that significant progress is needed in that area.