Stereospecific and Stereodivergent Construction of Quaternary Carbon Centers through Switchable Directed/Nondirected Allylic Substitution

摘要

The enantioselective construction of quaternary stereogenic carbon centers is a challenge in organic synthesis.Much progress has been made with enantioselective catalytic methods,but still no general solution to this synthetic problem exists.A reliable alternative strategy for the predictable installation of a quaternary stereocenter is 1,3-chirality transfer from a more readily accessible stereogenic center by a sigmatropic process,such as the Claisen rearrangement.However,the nature of the sigmatropic process sets structural limitations on the type of carbon nucleophile that can be transferred.Allylic substitution with organo-metallic carbon nucleophiles could provide a more general solution if all aspects of selectivity could be controlled.