Urea‐Induced Acid Amplification: A New Approach for Metal‐Free Insertion Chemistry

AbstractThe enhanced catalytic activity of difluoroboronate ureas proved to be essential as an acidity amplifier to promote metal‐free OH and SH insertion reactions of α‐aryldiazoacetates in high yield. This methodology was found to be generally applicable to a broad substrate scope and presents a conceptually new approach for organocatalytic diazo insertion reactions. Mechanistic investigations suggest that the reaction pathway involves a urea‐induced protonation of the α‐aryldiazoester.