Enantioselective Cu/Pd Cocatalyzed Allylboration of 1,3-Dienes

The development of efficient methodologies for the conversion of abundant 1,3-dienes into enantioenriched complex molecules remains a significant challenge and is highly desirable. In this work, we demonstrate the stereoselective coupling of B2(pin)2, 1,3-diene, and allyl carbonate utilizing a chiral sulfoxide-phosphine ligand in Cu/Pd cooperative catalysis. This transformation enables rapid access to borylated 1,5-dienes with two vicinal stereocenters, exhibiting chemo-, regio-, diastereo-, and enantioselectivity (up to 80% yield, 18:1 d.r., and 98% ee). The synthetic potential of the borylated 1,5-diene products has been demonstrated through a series of downstream product diversification experiments. Mechanistic studies, including both experimental approaches and DFT calculations, suggest an unconventional syn-SN2' allyl-to-allyl ligand attack from catalytically generated allylcopper to allylpalladium.