Asymmetric Friedel–Crafts Reaction of 4,7‐Dihydroindoles with Nitroolefins by Chiral Brønsted Acids under Low Catalyst Loading

• Published in: Chemistry : a European journal 2009-03, Vol.15 (14), p.3351-3354
• Main Authors: Sheng, Yi‐Fei, Li, Gong‐Qiang, Kang, Qiang, Zhang, An‐Jiang, You, Shu‐Li
• Format: Article
• Language: English
• Subjects: Alkenes - chemistry; asymmetric catalysis; Catalysis; chiral Brønsted acids; conjugate addition; enantioselectivity; Friedel–Crafts reaction; Indoles - chemistry; Phosphoric Acids - chemistry; Stereoisomerism
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200900033

Slowly does it! By adding the substrate by a syringe pump, a highly efficient Friedel–Crafts reaction of 4,7‐dihydroindoles with nitroolefins was realized with 0.5 mol % of a chiral phosphoric acid. The Friedel–Crafts alkylation, together with a subsequent oxidation of the product, led to 2‐substituted indoles in excellent enantiomeric excesses, which can be easily transformed to enantioenriched tetrahydro‐γ‐carbolines. Slowly does it! By adding the substrate by a syringe pump, a highly efficient Friedel–Crafts reaction of 4,7‐dihydroindoles with nitroolefins was realized with 0.5 mol % of a chiral phosphoric acid. The Friedel–Crafts alkylation, together with a subsequent oxidation of the product, led to 2‐substituted indoles in excellent enantiomeric excesses, which can be easily transformed to enantioenriched tetrahydro‐γ‐carbolines.