Regio‐ and Diastereoselective Rhodium‐Catalyzed Allylic Substitution with Unstabilized Benzyl Nucleophiles

Abstract

We have developed a highly regio‐ and diastereoselective rhodium‐catalyzed allylic substitution of challenging alkyl‐substituted branched allylic carbonates with benzylzinc reagents, which are prepared from widely available benzyl halides. This process utilizes rhodium(III) chloride as a commercially available, high‐oxidation state and bench‐stable pre‐catalyst to provide a rare example of regio‐ and diastereoselective allylic substitution in the absence of an exogenous ligand. This reaction tolerates both electronically diverse benzylzinc nucleophiles and an array of functionalized and/or challenging aliphatic secondary allylic electrophiles. Finally, the configurational fluxionality of the rhodium‐allyl intermediate is exploited to develop a novel diastereoselective process for the construction of vicinal acyclic ternary/ternary stereogenic centers, in addition to a cyclic ternary/quaternary derivative.