title: New versatile route to the synthesis of tetrahydro-beta-carbolines and tetrahydro-pyrano[3,4-b]indoles via an intramolecular Michael addition catalyzed by InBr3.
abstract: A simple multistep synthetic strategy to 4-substituted 1,2,3,4-tetrahydro-beta-carboline and 1,3,4,9-tetrahydro-pyrano[3,4-b]indole derivatives starting from commercially available indole 2-carboxylic acid (5) is described. The final intramolecular Michael addition promoted by catalytic amount of InBr(3) (5-10 mol %) provided the expected polycyclic compounds in excellent yields (up to 97%) both in anhydrous organic and aqueous media.
authors.affiliation: Dipartimento di Chimica G. Ciamician, Via Selmi 2, 40126 Bologna, Italy.
authors.forename: Marianna
authors.initials: M
authors.lastname: Agnusdei
authors.forename: Marco
authors.initials: M
authors.lastname: Bandini
authors.forename: Alfonso
authors.initials: A
authors.lastname: Melloni
authors.forename: Achille
authors.initials: A
authors.lastname: Umani-Ronchi