Indium trichloride catalyzed one-pot synthesis of indolo[2,1-a]pyrrolo[4′,3′:2,3]-7a,8,13,13b-tetrahydroquinolines through intramolecular imino Diels–Alder reactions

An efficient synthesis of tetrahydroquinolines has been achieved by the reaction of aldimines derived from various substituted aromatic amines and indole-2-carbaldehyde containing an internal dienophile using 20 mol % InCl3 in acetonitrile at room temperature. The reactions are very fast and the products are isolated in good yields and in pure form.