Synlett 2012(5): 699-705  
DOI: 10.1055/s-0031-1290132
ACCOUNT
© Georg Thieme Verlag Stuttgart ˙ New York

Bidentate Lewis Acids as Catalysts for the Activation of 1,2-Diazenes in Organic Synthesis

Hermann A. Wegner*, Simon N. Kessler
University of Basel, Department of Chemistry, St. Johanns-Ring 19, 4056 Basel, Switzerland
Fax: +41(61)2670976; e-Mail: hermann.wegner@unibas.ch;
Further Information

Publication History

Received 3 September 2011
Publication Date:
04 January 2012 (online)

Abstract

A new concept for the catalysis of the inverse-electron-demand Diels-Alder (IEDDA) reaction of 1,2-diazenes using bidentate Lewis acid was recently reported by our group. The general catalytic principle is based on the simultaneous coordination of the bidentate Lewis acid to the 1,2-diazene moiety, lowering the LUMO to facilitate the cycloaddition step. Extrusion of N2 regenerates the catalyst and after elimination the aromatic product is obtained. In this account the development of this new catalytic principle is described and put into the general context of Lewis acid catalysis.

1 Introduction

2 Interaction of Bidentate Lewis Acids with 1,2-Diazenes

3 Catalytic IEDDA Reaction of 1,2-Diazenes with a Bidentate Lewis Acid

3.1 The General Principle of Catalysis

3.2 Evaluation of the Concept by Calculations

3.3 Synthesis of the Bidentate Lewis Acid Catalyst

3.4 Characterization of the Bidentate Lewis Acid-1,2-Diazene Complex

3.5 Catalysis of the IEDDA Reaction of 1,2-Diazenes

3.6 General Trends

4 Conclusion