Modular Access to Quaternary ?-Hydroxyl Acetates by Catalytic Cross-Coupling of Alcohols

Quaternary alpha-hydroxyl acids and their derivatives have attracted considerable attention because of their unique and broad functionalities. Herein, we successfully established a selective and modular protocol to access quaternary alpha-hydroxyl acetates via dehydrogenative cross-coupling of 1,2-diols and primary alcohols by using tris-N-heterocyclic carbene iridium (tris-NHC-Ir, 0.05 mol %) complexes as catalysts and Ba(OH)2 as the base, along with the generation of byproducts water and hydrogen gas. A plausible mechanism involving dehydrogenation of alcohols, aldol-condensation, and 1,2-alkyl rearrangement reactions was proposed, in which 1,2-alkyl rearrangement was responsible for the construction of the quaternary carbon center.

Automated summary

A selective and modular protocol was developed for the synthesis of quaternary alpha-hydroxyl acetates via dehydrogenative cross-coupling of 1,2-diols and primary alcohols using tris-N-heterocyclic carbene iridium complexes as catalysts and Ba(OH)2 as the base. The reaction involves the generation of byproducts water and hydrogen gas, and a proposed mechanism includes dehydrogenation of alcohols, aldol condensation, and 1,2-alkyl rearrangement reactions for the construction of the quaternary carbon center.