Photocatalytic/Promoted Synthesis Of N-Heterocyclic Compounds Via EDA Complex

As the key structures of many drug molecules,nitrogenous heterocyclic compounds are widely present in numbers of natural products.Due to their broad spectrum of biological activities,the development of environmentally-friendly and efficient synthetic methods of nitrogenous heterocyclic compounds has become a hot topic.In this paper,we carried out the visible-light-induced multicomponent annulation reactions to synthesize two nitrogenous heterocyclic compounds without the addition of other transition metal catalysts.The scope of substrates and the possible reaction mechanism of the two photocatalytic strategies have been fully explored,the work is as follows:(1)We developed a visible light-induced three-component coupling cyclization reaction of amines,isothiocyanates and diethyl but-2-ynedioate to synthesize 2-iminothiazolidin-4-ones without external photocatalyst.The electron donor-acceptor(EDA)complex,detected by UV-vis spectroscopy,may act as the photocatalyst during the reaction.The method shows the characteristics of mild reaction conditions,good substrate adaptability,simple operation,and environmentally-friendly.(2)Based on the above work,we further tried to use diethyl but-2-ynedioate as the electron acceptor to react with N-methylaniline to synthesize indoles without external photocatalysts and metals via the formation of C-C/C-N bond,which promoted by visible light irradiation.EDA complexes are also formed during the reaction.The reaction has the advantages of mild reaction conditions,readily available starting materials and simple operation.The method has potential application value in the fields of organic synthesis and drug screening.