One-pot synthesis of substituted indoles via titanium(iv) alkoxide mediated imine formation – copper-catalyzed N-arylation

Readily accessible o-bromobenzylketones and primary alkyl amines and anilines were used for the construction of substituted indoles in good to excellent yields. The sequence involves a titanium-mediated reaction of ketones with amines to afford imines and subsequent intramolecular cyclization into indoles employing copper catalysis. The two-step protocol allows for the preparation of indoles bearing both N-alkyl and N-aryl groups as well as N-unsubstituted indoles without isolation of the intermediates and is tolerant of a wide range of functionality.