α-Silyl Controlled Asymmetric Michael Additions of Acyclic and Cyclic Ketones to Nitroalkenes

Dieter Enders; Thomas Otten

doi:10.1055/s-1999-2715

Synlett 1999; 1999(6): 747-749
DOI: 10.1055/s-1999-2715

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α-Silyl Controlled Asymmetric Michael Additions of Acyclic and Cyclic Ketones to Nitroalkenes

Dieter Enders^* , Thomas Otten

^*Institut für Organische Chemie, Professor-Pirlet-Straße 1, 52074 Aachen, Germany; Fax Int. +49 (2 41) 88 88-1 27; E-mail: Enders@RWTH-Aachen.de

Abstract

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Virtually enantiopure α-t-butyldimethylsilyl ketones (R)-1 and (S)-5 are converted regioselectively to the corresponding trimethylsilyl enol ethers (R)-2 and (S,Z)-6. Subsequent asymmetric Michael addition to nitroalkenes in the presence of SnCl₄ affords the 1,4-adducts 3 and 7 in good yields and high diastereo- and enantiomeric excesses. Removal of the t-butyldimethylsilyl group with n-Bu₄NF, THF, NH₄F/HF lead to the α,β-disubstituted γ-nitro ketones (S,R)-4 (de = 91-92%, ee >98%) and (R,S)-8 (de >96%, ee >98%) in very good overall yields.

asymmetric synthesis - Michael addition - α-silyl ketones - nitroalkenes - nitro ketones

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