Synlett 2012(1): 6-20  
DOI: 10.1055/s-0031-1290093
ACCOUNT
© Georg Thieme Verlag Stuttgart ˙ New York

SmI2-Mediated Carbonyl-Alkene Couplings for the Synthesis of Small Carbocyclic Rings

Hassan Y. Harb, David J. Procter*
School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
Fax: +44(0)161 2754939; e-Mail: david.j.procter@manchester.ac.uk;
Further Information

Publication History

Received 11 August 2011
Publication Date:
07 December 2011 (eFirst)

Abstract

The electron transfer reducing agent samarium diiodide (SmI2) mediates reductive carbonyl-alkene couplings to give small carbocyclic rings with high diastereocontrol. The substrate scope and mechanism of the reactions is discussed. The application of these versatile reactions in target synthesis is also described.

1 Introduction

2 SmI2-Mediated 4-exo-trig Carbonyl-Alkene Coupling

2.1 Cyclizations in the Absence of HMPA

2.2 Expanding the Scope of the Reaction

3 The Mechanism of Cyclization

3.1 The ‘Carbonyl First’ Mechanism

3.2 The Origin of anti Diastereoselectivity

4 Further Studies on the 4-exo-trig Carbonyl-Alkene Coupling

5 A Switch in Mechanism

5.1 The Cyclizations of Ketones

5.2 The ‘Alkene First’ Mechanism

5.3 Investigating the Scope of Ketone Cyclizations

5.4 Stereoselective ‘Alkene First’ Cyclization-Lactone Reduction Cascades: An Approach to Stolonidiol

6 SmI2-Mediated 3-exo-trig Carbonyl-Alkene Couplings

7 The Use of a Stereocontrol Element in 4-exo-trig Carbonyl-alkene Couplings

7.1 A Silyloxy Stereocontrol Element

7.2 A Silicon Stereocontrol Element

7.3 An Approach to the Pestalotiopsin and Taedolidol Natural Products

8 Conclusions