A practical synthetic route to functionalized THBCs and oxygenated analogues via intramolecular Friedel-Crafts reactions.
A practical catalytic approach to the synthesis of 4-substituted 1,2,3,4-tetrahydro-beta-carbolines (THBCs, 1) and 1,2,3,9-tetrahydropyrano[3,4-b]indoles (2) via InBr3-catalyzed intramolecular Friedel-Crafts (F-C) cyclization is described. The use of cross-metathesis reaction represents a direct route to the cyclization precursors and the use of InBr3 (5 mol%) allowed polycyclic indole compounds to be isolated in high yields under mild reaction conditions (rt, DCM, minutes). Finally, efforts toward the development of a stereocontrolled version of the present cyclization are presented, highlighting [salenAlCl] and bimetallic [(salenAlCl)2-InBr3] system as promising chiral Lewis acids (ee up to 60%).
Angeli
Marco
M
Dipartimento di Chimica G. Ciamician, Università di Bologna, via Selmi 2, 40126, Bologna, Italy.
Bandini
Marco
M
Garelli
Andrea
A
Piccinelli
Fabio
F
Tommasi
Simona
S
Umani-Ronchi
Achille
A
D002243:Carbolines / Q000138:chemical synthesis* / Q000737:chemistry*; D007202:Indicators and Reagents; D007211:Indoles / Q000737:chemistry; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction
D002243:Carbolines; D007202:Indicators and Reagents; D007211:Indoles