Asymmetric Induction at C(β) and C(α) of N-Enoylsultams by Organomagnesium 1,4-Addition/Enolate Trapping |
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Authors: | Wolfgang Oppolzer,Giovanni Poli,Arend J. Kingma,Christian Starkemann,G rald Bernardinelli |
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Affiliation: | Wolfgang Oppolzer,Giovanni Poli,Arend J. Kingma,Christian Starkemann,Gérald Bernardinelli |
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Abstract: | The 1,4-addition of alkylmagnesium chlorides to conjugated N-enoylsultams and subsequent ‘enolate trapping’ with aq. NH4Cl or MeI/hexamethylphosphoric triamide generated centers of asymmetry at C(β) and/or at C(α) with good to excellent π-face defferentiation as demonstrated by the conversions 1 → 2 , 1 → 4 , and 8 → 9 . This holds also for the regioselective 1,4-addition of EtMgC1 to a dienoylsultam ( 15 → 16 ). Reactive conformations 1 ≠, 8 ≠, 13 , and 14 are postulated in agreement with X-ray evidence which also served for the structure determination of the product 9j . |
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