A tin-free route to trans-diels-alder motifs by visible light photoredox catalysis.

A tin-free trans-Diels-Alder paradigm for the stereoselective synthesis of trans-fused polycyclic systems was developed through the photocatalytic reductive dehalogenation of α-haloketones promoted by visible light. Good to excellent diastereoselectivities were observed in the stereoselective construction of trans-fused octalone derivatives under mild reaction conditions.