Oxazaborolidinones: Steric Coverage Effect of Lewis Acidic Boron Center in Suzuki–Miyaura Coupling Reactions

Abstract

It was demonstrated that α‐hydroxycarboxamide is an excellent boron‐protecting group. The reaction between α‐hydroxycarboxamide and organoboronic acids produced stable oxazaborolidinones (OxBs), in which the ‐hybridized boron atom was sterically protected by α‐hydroxycarboxamide. The alkyl groups of the α‐hydroxycarboxamide moiety can dynamically cover the p‐orbital of the ‐hybridized boron center, creating a small space around the boron atom, allowing for smooth transmetalation by a Pd catalyst and easy deprotection by water. This protecting phenomenon is effective for readily purification, Suzuki–Miyaura coupling reactions with unstable boronic acids and iterative cross‐couplings.