Metal-free visible light driven synthesis of tetrahydroquinoline derivatives utilizing Rose Bengal

The visible-light driven reaction for the synthesis of tetrahydroquinoline derivatives via tandem radical cyclization of N,N-dimethylanilines with 2-benzylidenemalononitriles has been developed. Corresponding products were obtained with yields of up to 74% under mild conditions by using Rose Bengal as a triplet sensitizer, which is inexpensive, environmentally-friendly and easily acquired. This work demonstrates the potential benefits of Rose Bengal for the production of tetrahydroquinoline derivatives.