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Synthesis 2005(8): 1378-1382  
DOI: 10.1055/s-2004-834885
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© Georg Thieme Verlag Stuttgart · New York

Simple Preparation of Trans-Epoxides via Ylide Intermediates

Varinder K. Aggarwal*, Cristina Aragoncillo, Caroline L. Winn
School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
Fax: +44(117)9298611; e-Mail: v.aggarwal@bristol.ac.uk;
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Publication History

Received 24 August 2004
Publication Date:
21 October 2004 (online)

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Abstract

A practical route to epoxides with control of the relative and absolute stereochemistry has been developed, allowing epoxides to be readily prepared on a 20 mmol scale by generating the reactive intermediate (the diazo compound) in situ from benzaldehyde tosylhydrazone sodium salt. In this paper, we describe the optimum conditions for three procedures to obtain the desired racemic and enantiomerically enriched epoxides (Scheme [1] ). High diastereoselectivities (98-100%) and very high yields of epoxide were obtained. Asymmetric epoxidation was carried out using the chiral camphor-derived [2.2.1] bicyclic sulfide 4 and the desired epoxide was obtained with excellent enantioselectivity (94%).

Key words

asymmetric catalysis - diazo compounds - epoxidations - sulfur ylides - epoxides

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10

For the preparation of chiral sulfide 4, see ref.9