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Synthesis, characterization and enantioselective free radical reductions of (1R,2S,5R)-menthyldiphenylgermane and its enantiomer

Zeng, Le, Dakternieks, Dainis, Duthie, Andrew, Perchyonok, Tamara and Schiesser, Carl 2004, Synthesis, characterization and enantioselective free radical reductions of (1R,2S,5R)-menthyldiphenylgermane and its enantiomer, Tetrahedron : asymmetry, vol. 15, no. 16, pp. 2547-2554, doi: 10.1016/j.tetasy.2004.06.020.

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Title Synthesis, characterization and enantioselective free radical reductions of (1R,2S,5R)-menthyldiphenylgermane and its enantiomer
Formatted title Synthesis, characterization and enantioselective free radical reductions of (1R,2S,5R)-menthyldiphenylgermane and its enantiomer
Author(s) Zeng, Le
Dakternieks, Dainis
Duthie, Andrew
Perchyonok, Tamara
Schiesser, Carl
Journal name Tetrahedron : asymmetry
Volume number 15
Issue number 16
Start page 2547
End page 2554
Publisher Elsevier
Place of publication Amsterdam,, Netherlands
Publication date 2004-08-23
ISSN 0957-4166
1362-511X
Summary (1R,2S,5R)-Menthyldiphenylgermane and its enantiomer have been prepared in a few steps from germanium tetrachloride. The initial step in this sequence, namely the reaction between germanium tetrachloride and menthylmagnesium chloride, produces menthylgermanium trichloride, which is the exclusive product of this Grignard reaction, presumably due to the bulk of the menthyl group. When used at a low temperature (−78 °C) and in conjunction with Lewis acids, such as magnesium salts, these chiral germanes are capable of reducing ester functionalized radicals in high enantioselectivity, but in low-moderate yield. For example, (R)-naproxen ethyl ester was obtained in 15% yield and 99% ee by reaction in toluene of 2-bromonaproxen ethyl ester with (1R,2S,5R)-menthyldiphenylgermane in toluene at −78 °C in the presence of magnesium bromide. At 80 °C, (1R,2S,5R)-menthyldiphenylgermane reacted with primary alkyl radicals with a rate constant of 1.02 × 106 M−1 s−1. Kinetic studies reveal the Arrhenius expression for this reaction to be: log(k/M−1 s−1) = (11.1 ± 0.4) − (34.6 ± 3.1)/θ where θ=2.3RT kJ mol−1.


Language eng
DOI 10.1016/j.tetasy.2004.06.020
Field of Research 039904 Organometallic Chemistry
Socio Economic Objective 970103 Expanding Knowledge in the Chemical Sciences
HERDC Research category C1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2004, Elsevier
Persistent URL http://hdl.handle.net/10536/DRO/DU:30008743

Document type: Journal Article
Collection: School of Biological and Chemical Sciences
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