Enantioselective Synthesis of Oxazaborolidines by Palladium‐Catalyzed N−H/B−H Double Activation of 1,2‐Azaborines

Abstract

AbstractA palladium‐catalyzed N−H/B−H double activation of 1,2‐dihydro‐1,2‐benzazaborines proceeded via cycloaddition with vinyl ethylene carbonate to produce polycyclic oxazaborolidines in 31–96 % yield. The key step in this process is the release of molecular hydrogen from a borate intermediate. Using a SPINOL‐derived phosphoramidite as a chiral ligand, chiral oxazaborolidines were synthesized in good to high yields with excellent enantioselectivity (up to 95 % ee). The vinyl group of the resulting oxazaborolidine underwent metathesis, Heck reaction, and Wacker oxidation without affecting the oxazaborolidine framework.