Original scientific paper

Reduction of Ketones with LiAlH₄ Complexes of α,α,α',α'-Tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOLs) A Combination of Enantioselective Reduction and Clathrate Formation with a Discussion of LAH Reagents Bearing C₂-Symmetrical Ligands

Dieter Seebach ; Laboratorium für Organische Chemie der Eidgenössischen Technischen Hochschule, ETH-Zentrum, Universitátstrasse 16, CH-8092 Zürich, Switzerland
Albert K. Beck ; Laboratorium für Organische Chemie der Eidgenössischen Technischen Hochschule, ETH-Zentrum, Universitátstrasse 16, CH-8092 Zürich, Switzerland
Robert Dahinden ; Laboratorium für Organische Chemie der Eidgenössischen Technischen Hochschule, ETH-Zentrum, Universitátstrasse 16, CH-8092 Zürich, Switzerland
Matthias Hoffmann ; Laboratorium für Organische Chemie der Eidgenössischen Technischen Hochschule, ETH-Zentrum, Universitátstrasse 16, CH-8092 Zürich, Switzerland
Florian N. M. Kühnle ; Laboratorium für Organische Chemie der Eidgenössischen Technischen Hochschule, ETH-Zentrum, Universitátstrasse 16, CH-8092 Zürich, Switzerland

Abstract

A complex prepared from one equivalent each of LiAlH₄, EtOH and a TADDOL (α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanol) reduces aryl alkyl ketones to sec. alcohols with enantiomer ratios (er) up to 96 : 4. The chiral LAH derivative is used in two-fold excess in THF solution and at dry ice temperatures. The ability of TADDOLs to form clathrates diastereoselectively can be exploited to increase the er of the initially formed alcohols by a simple modification of the work-up procedure and hence, products of very high en- antiopurity (er 99 : 1) can be isolated. When (7i,/i)-TADDOLs (from (ZiA)-tartrate) are applied in the reaction, the 1-aryl-alkanols formed preferentially have (S) configuration, as for the products obtained with the corresponding (P)-BINOL and (P)-BIPHENOL derivatives. A common mechanistic model is discussed.

Keywords

Hrčak ID:

136667

URI

https://hrcak.srce.hr/136667

Publication date:

3.6.1996.

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