Synthesis of Tetrasubstituted Allenes via Visible-Light-Promoted Radical 1,3-Difunctionalization of Alkynyl Diazo Compounds.

Herein, we described an unprecedented process for generating allenyl radicals through radical addition to alkynyl diazo compounds followed by a 1,2-radical shift with the loss of nitrogen. Using this protocol, radical 1,3-difunctionalization of alkynyl diazo compounds for the synthesis of tetrasubstituted allenes with RSO 2 X (X = SeR', SR', and I) as the radical sources was developed. The reactions were promoted by visible light without photocatalyst and any additives.