Conjugate Addition of Indoles to α,β-Unsaturated Ketones Using a Brønsted Acid Ionic Liquid as an Efficient Catalyst

The Brønsted acid ionic liquid [PyN(CH(2))(4)SO(3)H][p-CH(3)PhSO(3)] has been reported as an efficient catalyst for the Michael addition reaction of indoles to α,β-unsaturated ketones. Satisfactory results were obtained, with excellent yields and a simple experimental procedure. The catalyst could be recycled and reused up to three times without any noticeable decrease in the catalytic activity.