Asymmetric Synthesis of α′-Silylated α,β-Epoxy Ketones via Darzens Reaction

Dieter Enders; Robert Hett

doi:10.1055/s-1998-1832

Synlett 1998; 1998(9): 961-962
DOI: 10.1055/s-1998-1832

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Asymmetric Synthesis of α′-Silylated α,β-Epoxy Ketones via Darzens Reaction

Dieter Enders^* , Robert Hett

^*Institut für Organische Chemie, Rheinisch-Westfälische Technische Hochschule, Professor-Pirlet-Straße 1, D-52074 Aachen, Germany; Fax (int.)+ 2 41 88 88 1 27; E-mail: Enders@RWTH-Aachen.de

Abstract

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The diastereo- and enantioselective synthesis of α′-silylated α,β-epoxy ketones via Diarzens reaction is described. Using the SAMP/RAMP-hydrazone method α′-silylated α-bromo ketones (S)-4 a and b were formed as enantiomerically pure starting materials for the Darzens reaction with various aldehydes. The trans-epoxy ketones (S,S,R)-6 a - g were obtained in good yields (55-80%) and with poor to good diastereomeric excesses (de = 0-90%). Separation of diastereomers led to the enantiomerically pure title compounds (de,ee ≥ 95%). In addition the Darzens reaction between the protected glyceraldehyde (R)-7 and α-bromopinacolone (8) afforded the cis-epoxy ketone (R,R,R)-9 (de,ee ≥ 95%).

asymmetric Synthesis - Darzens reaction - epoxy ketones - SAMP/RAMP-hydrazone method - α-silylated bromo ketones

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