Highly Diastereo‐ and Enantioselective Synthesis of 3,6′‐Bisboryl‐ anti ‐1,2‐oxaborinan‐3‐enes: An Entry to Enantioenriched Homoallylic Alcohols with A Stereodefined Trisubstituted Alkene

A Cu‐catalyzed regio‐, diastereo‐, and enantioselective carboboration of 1,1‐bisboryl‐1,3‐butadiene is developed to generate enantioenriched 3,6′‐bisboryl‐anti‐1,2‐oxaborinan‐3‐enes. DFT calculations indicate that the initial diene 1,2‐borocupration forms a 3 η‐allylic copper as the most stable intermediate. Subsequent aldehyde addition, however, operates under Curtin–Hammett control via a more reactive α,α‐bisboryl tertiary allylcopper species to furnish products with high enantioselectivities. The three boryl groups in the products are properly differentiated and can undergo a variety of chemoselective transformations to produce enantioenriched homoallylic alcohols with a stereodefined trisubstituted alkene.