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Single enatiomer free-radical chemistry - Lewis acid-mediated reductions of racemic halides using chiral non-racemic stannanes

journal contribution
posted on 2003-10-03, 00:00 authored by Dainis Dakternieks, V Perchyonok, C Schiesser
Additions of one to two equivalents of Lewis acids that include magnesium salts to free-radical reduction reactions involving ester functionalized radicals and (1R,2S,5R)-menthyldiphenyltin hydride 4, bis((1R,2S,5R)-menthyl)phenyltin hydride 5, tris((1R,2S,5R)-menthyl)tin hydride 6, bis((1R,2S,5R)-menthyl)-[8-(N,N-dimethylamino)naphthyl]tin hydride 12, bis((1R,2S,5R)-menthyl)-[1-((S)-N,N-dimethylaminoethyl)phenyl]tin hydride 13 or 3α-dimethylstannyl-5α-cholestane 14 result in remarkable enantioselectivities. Examples include (S)-naproxen ethyl ester 16, produced in 74% yield and greater than 99% ee at −78°C from the bromide and 5 in the presence of MgBr2, and ethyl (R)-N-trifluoroacetyl-D-phenylglycinate 18, obtained in 78% yield and 99% ee under identical conditions. Kinetic and computational studies provide insight into the origins of these observations.


History

Journal

Tetrahedron: asymmetry

Volume

14

Issue

19

Pagination

3057 - 3068

Publisher

Elsevier

Location

Amsterdam, The Netherlands

ISSN

0957-4166

eISSN

1362-511X

Language

eng

Notes

Available online 19 September 2003.

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2003, Elsevier Ltd.

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