Synlett 2008(16): 2389-2399  
DOI: 10.1055/s-2008-1078016
ACCOUNT
© Georg Thieme Verlag Stuttgart ˙ New York

Preparation of Five-Membered Rings via the Translocation-Cyclization of Vinyl Radicals

Fabrice Dénès*a, Florent Beaufilsb, Philippe Renaud*b
a Laboratoire CEISAM, UMR CNRS 6230, Faculté des Sciences et des Techniques, Université de Nantes, 2 rue de la Houssinière, BP 92208, 44322 Nantes, Cedex 3, France
e-Mail: fabrice.denes@univ-nantes.fr;
b Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, 3000 Berne 9, Switzerland
Fax: +41(31)6313426; e-Mail: philippe.renaud@ioc.unibe.ch;
Further Information

Publication History

Received 31 March 2008
Publication Date:
31 July 2008 (online)

Abstract

Vinyl radicals have a propensity to rearrange via intramolecular 1,5-hydrogen transfer to the more-stable alkyl radicals, which themselves possess a suitable structure to undergo rapid 5-exo-trig cyclizations. This tandem radical translocation-cyclization process represents a useful tool for the preparation of a wide range of five-membered rings. Moreover, this reaction is highly selective and, due to its radical nature, tolerates a variety of functional groups. During the last decade, tin-free procedures have emerged, rendering this process very attractive for the synthesis of natural products and their analogues. Selected examples of this strategy illustrating the scope of the method are described.

1 Introduction

2 Vinyl Radicals from Vinyl Halides

3 Vinyl Radicals Generated by Addition to Alkynes and
Allenes

3.1 Addition of Carbon-Centered Radicals

3.1.1 Intermolecular Addition of Carbon-Centered Radicals

3.1.2 Intramolecular Addition of Carbon-Centered Radicals

3.2 Addition of Tin-Centered Radicals

3.3 Addition of Oxygen-Centered Radicals

3.4 Addition of Nitrogen-Centered Radicals

3.5 Addition of Sulfur-Centered Radicals

3.6 Addition of Phosphorus-Centered Radicals

4 Translocation-Cyclization Processes Involving a Stereo­selective Hydrogen Atom Transfer

5 Conclusion