Visible light photoredox organocatalysis: a fully transition metal-free direct asymmetric α-alkylation of aldehydes

Rose Bengal, a dye sensitizer, was found to be active as a visible light photoredox catalyst for the direct enantioselective α-alkylation of aldehydes in environmentally benign and simple conditions. Starting from a SOMO converse mechanism, the catalytic activity of the imidazolidinone organocatalyst was improved using an electrophilic cocatalyst. The resulting methodology and optimal conditions led to efficient and transition-metal-free direct photoredox organocatalysis.