Asymmetric Michael Additions via SAMP‐/RAMP‐Hydrazones Enantioselective Synthesis of β‐Substituted Δ‐Oxopentanoates and δ‐Lactones<sup>1)</sup>

Dieter Enders, Beatrice E. M. Rendenbach

doi:10.1002/cber.19871200718

Asymmetric Michael Additions via SAMP‐/RAMP‐Hydrazones Enantioselective Synthesis of β‐Substituted Δ‐Oxopentanoates and δ‐Lactones<sup>1)</sup>

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<jats:title>Abstract</jats:title><jats:p>Asymmetric Michael addition of metalated acetaldehyde SAMP‐ or RAMP‐hydrazone (<jats:italic>S</jats:italic>)‐ or (<jats:italic>R</jats:italic>)‐<jats:bold>2</jats:bold> to α,β‐unsaturated esters <jats:bold>3</jats:bold> and subsequent oxidative cleavage by ozonolysis yields the β‐substituted δ‐oxopentanoates (<jats:italic>R</jats:italic>)‐ or (<jats:italic>S</jats:italic>)‐<jats:bold>5</jats:bold> with high enantiomeric excesses (ee = 90 to ≧ 96%). Racemization‐free reduction and cyclization affords the corresponding optically active δ‐lactones (<jats:italic>R</jats:italic>)‐ or (<jats:italic>S</jats:italic>)‐<jats:bold>7</jats:bold>.</jats:p>