Pd-H/Lewis base cooperative catalysis confers asymmetric allylic alkylation of esters atom-economy and stereodivergence

Abstract

The construction of Csp³-Csp³ with high stereoselectivity, even in a stereodivergent way, has been a long-standing theme in organic synthesis. As an atom- and step-economic transformation, transition metal hydride-mediated allylic alkylation of enolizable carbonyl compounds with readily available allenes, alkynes or 1,3-dienes as the unconventional allylating reagents has recently emerged as a promising protocol for the stereoselective construction of Csp³-Csp³ bonds with high efficiency. Due to their less enolizability and weak nucleophilicity, simple esters remain challenging substrates for these coupling reactions. On the other hand, the strategy of metal/organo combined catalysis has recently emerged as one of the wide-ranging disciplines and powerful tools in asymmetric synthesis. Considering the recent achievements of chiral Lewis base catalysis in catalytic asymmetric α-functionalization of esters through a “rebound” mechanism, the cooperative combination of chiral Lewis bases and metal hydride catalysis may offer great opportunities to the aforementioned chemistry. Recently, the groups of Snaddon and Zi have made remarkable progresses in this area through palladium and chiral Lewis base cooperative catalysis.

Keywords

Combined catalysis / chiral Lewis base / asymmetric catalysis / allenes / dienes

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