Iron(III) chloride catalyzed synthesis of highly substituted indolyl-tetrahydroquinoline derivatives by using indolylnitroalkene as dienophiles and its application to the synthesis of indolo-benzonaphthyridine derivatives

An efficient iron(III) chloride catalyzed synthesis of highly substituted indolyltetrahydroquinoline derivatives from easily available starting materials, including indolylnitroalkenes, substituted anilines and various aldehydes is reported. The reaction utilized strong electron deficient dienophiles like indolylnitroalkene via a Povarov approach. The methodology shows good functional group tolerance and can be used to prepare fused indolo-benzonaphthyridine derivatives.