Iron-Catalyzed Synthesis of Aminoindolizines and Quinolines

Significance

Reported is the iron-catalyzed multicomponent synthesis of aminoindolizine and quinoline products. This reaction was developed as a result of the observation of a byproduct in previous work. Mechanisms for both reactions are proposed and are for the most part reasonable; however, no evidence for these mechanisms was given. In scheme 2 of the original paper the structure of the tricyclic products is incorrectly drawn, leading to confusion. The investigation of the substrate scope was modest but shows the reaction is reasonably general. In the formation of indolizines the use of aromatic alkynes with para electron-withdrawing groups gave lower yields as did the use of thiophenyl alkynes. Indolizine formation failed when aliphatic alkynes were used. In the formation of quinolines, aromatic aldehydes with electron-withdrawing groups and aliphatic aldehydes gave lower yields.