Magnesium amide base-mediated enantioselective deprotonation processes

Kerr, W.J. and Henderson, K.W. and Moir, J.H. (2002) Magnesium amide base-mediated enantioselective deprotonation processes. Tetrahedron, 58 (23). pp. 4573-4587. ISSN 0040-4020

Abstract

A novel homochiral magnesium bisamide has been readily prepared and, following careful optimisation, this species has been shown to react efficiently with a series of prochiral 4-substituted cyclohexanones in the presence of TMSCl to give the corresponding silyl enol ethers in enantiomeric ratios of up to 95:5. Additionally, the same chiral base system has been shown to be highly effective in the desymmetrisation of cis-2,6-disubstituted cyclohexanones, providing excellent levels of both conversion and enantioselection (up to >99.5:0.5 er). Furthermore, the magnesium bisamide has also been shown to mediate a kinetic resolution process with the corresponding trans-disubstituted substrates, allowing access to enantioenriched enol ethers and ketones.

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