Copper-Catalyzed Regio‑,\nDiastereo‑,\nand Enantioselective Allylic Alkylation with 1,1-Diborylalkanes

We report a copper-catalyzed regio-,\ndiastereo-, and\nenantioselective\nallylic alkylation of allyl bromides using 1,1-diborylalkanes as prochiral\nnucleophiles. This methodology employs copper(I) bromide as a catalyst,\nan (<i>R</i>)-BINOL-derived phosphoramidite as a ligand,\nand lithium benzoate as a crucial additive. The reaction affords enantioenriched\nhomoallylic boronic esters possessing vicinal stereocenters in good\nyields and high diastereo- and enantioselectivity. The developed method\ndemonstrates a broad substrate scope with respect to a wide range\nof 1,1-diborylalkanes and allyl bromides. Mechanistic studies, including\ndeuterium-labeling experiments and DFT calculations, provide insights\ninto the reaction pathway and the origin of the stereoselectivity.\nThe synthetic utility of this method is showcased through various\ntransformations of the obtained enantioenriched homoallylic boronic\nesters into valuable chiral building blocks.