Photoinduced three-component coupling reactions of electron deficient alkenes, dienes and active methylene compounds.

The irradiation of aqueous acetonitrile solutions, containing electron deficient alkenes, dienes and active methylene compounds along with sodium or cesium carbonate and catalytic amounts of phenanthrene or pyrene, gives rise to the formation of novel three-component coupling products and diene dimers. Cinnamonitrile and benzylidenemalononitrile and its derivatives serve as electron-acceptors; 2,5-dimethyl-2,4-hexadiene and malononitrile anion serve as electron donors in this process. Based on the results of UV-vis absorption spectroscopy and the calculated ΔG values for single electron transfer (SET), mechanisms are proposed for the coupling reaction involving photoinduced electron transfer (PET) between the electron deficient alkenes and dienes or malononitrile anion via direct excitation of electron deficient alkenes or redox photosensitization using phenanthrene or pyrene serving as a photosensitizer.