Quinone imine dye formation via photocycloaddition between isocyanates and chloranil

Photochemical [2+2]cycloaddition between electron-donating aryl isocyanates and chloranil was observed in acetonitrile or benzene, and the following elimination of carbon dioxide resulted in the formation of the corresponding quinone imine dyes. This new route for synthesis of quinone imine was investigated by product analyses, laser flash photolyses, and molecular orbital calculation.