Brønsted Acid-Assisted Lewis Acid Mediated Intramolecular Trapping of Aminoenol with Activated Alkenes and Ketones.

An efficient Brønsted acid-assisted Lewis acid-mediated synthesis of indolines and pyrrolidines has been achieved from α-hydroxydimethylacetals and suitable electrophile-tethered amines. The reaction proceeds via an interrupted Amadori/Heyns rearrangement, where the key aminoenol intermediate was successfully trapped with Michael acceptors and ketones in an intramolecular fashion to afford corresponding derivatives in good yield and diastereoselectivity. The reaction is operationally simple, general, and tolerates various functional groups.