Unlocking the Nucleophilicity of Strong Alkyl C–H Bonds via Cu/Cr Catalysis

Direct functionalization of inert C–H bonds is one of the most attractive yet challenging strategies for constructing molecules in organic chemistry. Herein, we disclose an unprecedented and Earth abundant Cu/Cr catalytic system in which unreactive alkyl C–H bonds are transformed into nucleophilic alkyl–Cr(III) species at room temperature, enabling carbonyl addition reactions with strong alkyl C–H bonds. Various aryl alkyl alcohols are furnished under mild reaction conditions even on a gram scale. Moreover, this new radical-to-polar crossover approach is further applied to the 1,1-difunctionalization of aldehydes with alkanes and different nucleophiles. Mechanistic investigations reveal that the aldehyde not only acts as a reactant but also serves as a photosensitizer to recycle the Cu and Cr catalysts.