Synlett 2010(9): 1289-1301  
DOI: 10.1055/s-0029-1219929
ACCOUNT
© Georg Thieme Verlag Stuttgart ˙ New York

Asymmetric Friedel-Crafts Alkylation of Indoles: The Control of Enantio- and Regioselectivity

Mi Zeng, Shu-Li You*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, P. R. of China
Fax: +86(21)54925087; e-Mail: slyou@sioc.ac.cn;
Further Information

Publication History

Received 14 December 2009
Publication Date:
10 May 2010 (online)

Abstract

The asymmetric Friedel-Crafts reaction of indoles is a synthetic methodology that enables direct access to the enantiopure indole derivatives. In this review, work mainly carried out by You and his co-workers on the regio- and enantioselective synthesis of indole derivatives will be discussed. Chiral Brønsted acids or iridium complexes promote highly enantioselective Friedel-Crafts reactions of indoles and 4,7-dihydroindoles starting with various electrophilic reagents, such as imines, N-tosyl-substituted amines, β,γ-unsaturated α-keto esters, nitro-substituted olefins, aldehydes, and allyl carbonates. These methodologies can be used to readily prepare diverse enantioenriched indoles, such as indol-3-ylmethanamines, indol-2-ylmethanamines, unsymmetrical arylbis(indol-3-yl)methanes, 9-indol-3-ylfluorenes, tetrahydropyrano[3,4-b]indoles, tetrahydro-γ-carbolines, and tetrahydro-β-carbolines.

1 Introduction

2 Asymmetric Friedel-Crafts Alkylation of Indoles at the ­3-Position

2.1 Chiral Phosphoric Acids and Their Activation Mode

2.2 Asymmetric Friedel-Crafts Alkylation of Indoles with ­Imines

2.3 Asymmetric Friedel-Crafts Alkylation of Indoles with N-Tosyl-Substituted Amines

2.4 Tandem Friedel-Crafts Alkylation of Indoles with Aldehydes and Alcohols

2.5 Iridium-Catalyzed Asymmetric Friedel-Crafts Allylic Alkylation of Indoles

3 Asymmetric Friedel-Crafts Alkylation of Indoles at the 2-Position

3.1 Asymmetric Friedel-Crafts Alkylation of 4,7-Dihydro­indoles with Imines

3.2 Asymmetric Friedel-Crafts Alkylation of 4,7-Dihydro­indoles with Keto Esters

3.3 Asymmetric Friedel-Crafts Alkylation of 4,7-Dihydro­indoles with Nitro-Substituted Olefins

4 Sequential Catalysis for the Enantioselective Synthesis of Polycyclic Indoles

5 Conclusion and Outlook