Regio- and Stereoselective Synthesis of Multi-Alkylated Allylic Boronates through Three-Component Coupling Reactions between Allenes, Alkyl Halides, and a Diboron Reagent

Multisubstituted allylic boronates are attractive and valuable precursors for the rapid and stereoselective construction of densely substituted carbon skeletons. Herein, we report the first synthetic approach for differentially 2,3,3-triallcyl-substituted allylic boronates that contain a stereodefined tetrasubstituted alkene structure. Copper(I)-catalyzed regio- and stereoselective three-component coupling reactions between gem-dialkylallenes, alkyl halides, and a diboron reagent afforded sterically congested allylic boronates. The allylboration of aldehydes diastereoselectively furnished the corresponding homoallylic alcohols that bear a quaternary carbon. A computational study revealed that the selectivity-determining mechanism was correlated to the coordination of a boryl copper(I) species to the allene substrate as well as the borylcupration step.

Automated summary

Multisubstituted allylic boronates are valuable precursors for constructing densely substituted carbon skeletons. The regio- and stereoselective coupling reactions between gem-dialkylallenes, alkyl halides, and a diboron reagent can lead to sterically congested allylic boronates. Computational study revealed that the selectivity-determining mechanism is correlated to the coordination of a boryl copper(I) species to the allene substrate as well as the borylcupration step.