Electroreductive formylation of activated alcohols via radical-polar crossover

The direct synthesis of sterically hindered aldehydes is highly challenging. Herein, we report a direct approach to generate such compounds via electroreductive cleavage of the C(sp³)-O bond of activated alcohols. Under the established reaction conditions, benzylic radical intermediates were efficiently generated. A subsequent radical-polar crossover generated carbanions that further reacted with N,N-dimethylformamide to form various aldehydes with tertiary or quaternary benzylic carbon centers. The feasibility of a gram-scale synthesis was also demonstrated. This reaction is also operated in a simple undivided cell, which avoids the use of any transition metal catalysts, toxic gas, and reductants.