- Asymmetric Sulfinylations of N-Methylephedrine-Modified Tri- or Tetraalkyl Zincates by Symmetric Diaryl Sulfoxides
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Diethylzinc was treated with 1 or 2 equiv. of AlkMgCl or PhMgBr (preferably) or with 1 equiv. of nBuLi (less efficiently) for forming species – plausibly zincates – which were sulfinylated by diaryl sulfoxides to give racemic alkyl aryl sulfoxides in yields reaching 100 %. Dialkylzinc reagents were also activated by treatments with 1 or 2 equiv. of an enantiomerically pure alkylmagnesium β-aminoalkoxide. This worked best when the alkoxide stemmed from a dialkylmagnesium reagent and an equimolar amount of N-methyl-(–)-ephedrine. This second activation mode allowed sulfinylations of what was originally the dialkylzinc reagent with diaryl sulfoxides. This generated alkyl aryl sulfoxides with enantiomeric ratios up to 93:7 in up to 100 % yield.
- Ruppenthal, Simon,Brückner, Reinhard
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supporting information
p. 2518 - 2530
(2018/06/11)
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- The Reductive Cleavage of Cyclic Aminol Ethers to N,N-Dialkylamino-derivatives: Modifications to the Eschweiler-Clarke Procedure
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The reductive cleavage of cyclic aminol ethers to give N-alkylamino-derivatives in very high yields can be achieved using chlorotrimethylsilane in the presence of sodium cyanoborohydride: in the case of cyclic aminol ethers derived from formaldehyde the Eschweiler-Clarke reaction can be carried out in formic acid heated under reflux in the absence of formaldehyde.
- Page, Philip C. Bulman,Heaney, Harry,Rassias, Gerasimos A.,Reignier, Serge,Sampler, Edward P.,Talib, Salem
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p. 104 - 106
(2007/10/03)
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- Nitriles under palladium-catalyzed hydrogenation conditions as substitutes for aldehydes in the reaction with 1,2-amino alcohols: Formation of 1,3-oxazolidines and reductive N-alkylation
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At room temperature, the presence of hydrogen and catalytic amounts of Pd/C induced the formation of 1,3-oxazolidines from nitriles and 1,2-amino alcohols. The subsequent reductive cleavage of the NC-O bond of these heterocycles occurred under the same conditions. Thus, this methodology provides a new one-pot N-alkylation of 19-amino alcohols using nitriles as reagents with yields up to 98%.
- Henin, Francoise,Letinois, Stephane,Muzart, Jacques
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p. 7187 - 7190
(2007/10/03)
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- Reactions of (-)-Ephedrine, (+)-Norpseudoephedrine and Derivatives with N,N-Dimethylacetamid-dimethylacetal and N,N-Dimethylformamid-dimethylacetal
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The reactivity of (-)-ephedrine (2) and (+)-norpseudoephedrine (3) towards the amid-acetals 1 a/b has been studied.Both 2 and 3 were acetylated resp. formylated at first at the amino group.Nevertheless, derivatives of 2 and 3 possessing a trisubstituted amino group react with 1 a in a sigmatropic rearrangement to ortho substituted dimethylcarbamoylmethyl derivatives.By subsequent reduction with lithiumaluminiumhydride the aromatic compounds 8, 13, and 18 with two aminoethyl groups are easily available.In contrast to these results 1 b did not furnish any rearrangement products. Keywords. (-)-Ephedrine; (+)-Norpseudoephedrine; N,N-Dimethylacetamid-dimethylacetal; N,N-Dimethylformamid-dimethylacetal; Sympathomimetic effects; Sigmatropic rearrangements.
- Koehl, M,Spreitzer, H.,Fleischhacker, W.
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p. 911 - 918
(2007/10/02)
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