In the presence of 60 equivalents of HMPA, the condensation of the racemic allenylzinc derived from 1-chloro-3-trimethylsilylpropyne onto enantiopure non-alpha-branched N-tert-butanesulfinimines was proven to give access to the corresponding cis-ethynylaziridines as the major products. The good cis selectivity observed presumably resulted from a high kinetic resolution with the allenylzinc being partially configurationally labile with respect to the time scale defined by the rate of the reaction. Both single crystal X-ray analysis and semiempirical calculations conducted at the MM2 and AM1 levels of theory proved that the reaction certainly occurred through a preferred synclinal transition state in a supra- or antarafacial S(E)2' process. In all cases, chromatographic purification over silica gel allowed the cis-ethynyl-N-tert-butanesulfinylaziridines to be obtained as diastereo- and enantiomerically pure compounds (dr >98:2 and ee >99%).
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http://dx.doi.org/10.1002/chem.200500268 | DOI Listing |
J Org Chem
September 2009
UPMC-Univ Paris 06, CNRS UMR 7201, Institut Parisien de Chimie Moléculaire (FR 2769), case 183, 4 place Jussieu, F-75005 Paris, France.
An efficient methodology for the synthesis of sphingoid-type bases is reported. It involves the stereoselective addition of a racemic 3-alkoxy allenylzinc to enantiopure N-tert-butylsulfinyl imines and a cross-metathesis reaction as the key steps. It has been successfully applied to the syntheses of sphinganine and naturally occurring bioactive related compounds, among which the hydrolysis product of clavaminol H and two spisulosines.
View Article and Find Full Text PDFOrg Lett
February 2009
UPMC Univ Paris 06, UMR7611, Laboratoire de Chimie Organique, Institut de Chimie Moléculaire (FR2769), case 183, 4 place Jussieu, F-75252 Paris Cedex 05, France.
The high-yielding and highly efficient stereoselective synthesis of enantiopure anti,anti and syn,anti acetylenic 2-amino-1,3-diol stereotriads from alpha-alkoxy-tert-butanesulfinylimines bearing a stereocenter alpha to the imino group is reported. The stereoselectivity of the reaction of these tert-butanesulfinyl (tBS)-imines with allenylzinc (+/-)-1 was found to be controlled only by the configuration of the tBS group. An excellent kinetic resolution of the racemic allenylzinc species was observed, allowing a high stereocontrol no matter what the configuration or the protecting group of the alpha-alkoxy group.
View Article and Find Full Text PDFChemistry
September 2005
Laboratoire de Chimie Organique, UMR 7611, Université Pierre et Marie Curie, Tour 44-45, 2ème étage, Boîte 183, 4 place Jussieu, 75252 Paris Cedex 05, France.
In the presence of 60 equivalents of HMPA, the condensation of the racemic allenylzinc derived from 1-chloro-3-trimethylsilylpropyne onto enantiopure non-alpha-branched N-tert-butanesulfinimines was proven to give access to the corresponding cis-ethynylaziridines as the major products. The good cis selectivity observed presumably resulted from a high kinetic resolution with the allenylzinc being partially configurationally labile with respect to the time scale defined by the rate of the reaction. Both single crystal X-ray analysis and semiempirical calculations conducted at the MM2 and AM1 levels of theory proved that the reaction certainly occurred through a preferred synclinal transition state in a supra- or antarafacial S(E)2' process.
View Article and Find Full Text PDFJ Org Chem
November 2004
UMR 7611, Laboratoire de Chimie Organique, Université Pierre et Marie Curie, Tour 44-45, Case 183, 4 Place Jussieu, 75252 Paris Cedex 05, France.
Enantiopure trans-ethynyl N-tert-butanesulfinylaziridines (R(S))-6 were prepared in good to excellent yields by the condensation of the racemic allenylzinc species 1 derived from 3-chloro-1-trimethylsilylpropyne onto the corresponding enantiopure N-tert-butanesulfinimines (R(S))-5. The absolute stereochemistry of enantiopure N-tert-butanesulfinylaziridines (R(S))-6 was shown to be (R(S),2R,3R) and results from a chelate-type transition state in which the zinc atom of allenylzinc 1 is coordinated by both the nitogen and the oxygen atoms of the imine. Further removal of the N-tert-butanesulfinyl auxiliary of alkyl 3-substituted and 3,3-disubstituted ethynyl N-tert-butanesulfinylaziridines (R(S))-6 could be achieved by treatment with HCl in MeOH affording the corresponding deprotected aziridines (2R,3R)-9 and (2R)-9 respectively as enantiomerically pure compounds.
View Article and Find Full Text PDFJ Org Chem
December 2000
Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA.
Allenylzinc and indium reagents were generated in situ through Pd(0)-catalyzed metalation of (R)- and (S)-3-butyn-2-ol methanesulfonate with Et(2)Zn and InI. These reagents add to the benzyl and TBS ethers of (S)-lactic aldehyde to afford diastereomeric stereotriads in moderate to high yield. The (S)/(S) combination afforded the anti,anti adducts with 94:6-100:0 diastereoselectivity.
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