Chiral Phosphoric Acid Catalyzed Asymmetric Friedel–Crafts Alkylation of Indoles with Nitroolefins

Abstract

Asymmetric Michael-type Friedel–Crafts (F–C) alkylations of indoles with nitroolefins catalyzed by a chiral H₈-BINOL-based phosphoric acid were investigated. The reactions took place very smoothly in the presence of only 5 mol-% of catalyst at room temperature to afford the desired F–C alkylation products in good yields and with moderate enantioselectivities.

GRAPHICAL ABSTRACT

Keywords:

• Asymmetric Friedel–Crafts alkylations
• enantioselectivities
• chiral phosphoric acid
• indoles
• nitroolefins

Acknowledgments

This work is supported by Tianjin Natural Science Foundation (08JCYBJC26900), the Research Fund for Young Scientist (No. 52LX29), Tianjin Normal University, and Tianjin High School Foundation for Development of Science and Technology (2008ZD09).