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Enantioselective reduction of ketones with $NaBH_4$/diglyme possibly catalyzed by trialkyl borate: optically active sec-alcohols from prochiral ketones with catalytic (-)-menthol: autocatalysis option.

Chandrasekhar, Sosale and Hota, Raghunandan (2005) Enantioselective reduction of ketones with $NaBH_4$/diglyme possibly catalyzed by trialkyl borate: optically active sec-alcohols from prochiral ketones with catalytic (-)-menthol: autocatalysis option. In: Tetrahedron: Asymmetry, 16 (4). pp. 751-754.

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Abstract

Ketones can be reduced with $NaBH_4$ in diglyme without an apparent proton source, but putatively catalyzed by a trialkyl borate. This can be initially derived in situ from $NaBH_4$ and an alc., although the reaction becomes increasingly autocatalytic with time. With (-)-menthol as the initiating alc., the enantioselective redns. of a range of prochiral ketones in quant. yields and moderate ees (generally 58-87%) were realized (the autocatalysis was demonstrated in two cases; catalysis by tris-(-)-menthyl borate was demonstrated in one case). The mechanism may involve either the activation of the substrate (electrophilically) or of the hydride reagent (nucleophilically). This method offers a relatively simple and inexpensive approach to a key transformation in asymmetric synthesis.

Item Type: Journal Article
Additional Information: The Copyright belongs to Elsevier.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Date Deposited: 09 Mar 2006
Last Modified: 19 Sep 2010 04:24
URI: http://eprints.iisc.ernet.in/id/eprint/5805

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