Base-free, tunable, Au-catalyzed oxidative esterification of alcohols in continuous flow

Abstract

Under continuous flow conditions, hydrogen peroxide oxidizes primary alcohols (cinnamyl alcohol, decenol, decanol and benzyl alcohol) in methanol over Au/TiO₂, without the need for added base. While the allylic alcohols afforded conjugated aldehydes, aliphatic and benzylic alcohols afforded acids or esters. Selectivity for either product can be achieved by adjusting the reaction parameters. Kinetic studies revealed that the formation of the easter is faster than that of the acid, due to a greater pre-organization (larger ln A) attributed to the more favourable formation of the hemiacetal intermediate.