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

We have developed a highly regio- and diastereoselective rhodium-catalyzed allylic substitution of challenging alkyl-substituted secondary 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 a regio- and diastereoselective allylic substitution in the absence of an exogenous ligand. This reaction tolerates electronically diverse benzylzinc nucleophiles and an array of functionalized and/or challenging aliphatic 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.

Automated summary

The developed method utilizes rhodium catalysis for regio- and diastereoselective allylic substitution reactions, demonstrating high selectivity without the need for exogenous ligands. It is tolerant of various benzylzinc nucleophiles and functionalized aliphatic allylic electrophiles. Additionally, it exploits the configurational fluxionality of the rhodium-allyl intermediate for the construction of vicinal acyclic ternary/ternary stereogenic centers and cyclic ternary/quaternary derivatives.