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Computational investigations on the general reaction profile and diastereoselectivity in sulfur ylide promoted aziridination

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Title Computational investigations on the general reaction profile and diastereoselectivity in sulfur ylide promoted aziridination
 
Creator JANARDANAN, D
SUNOJ, RB
 
Subject density-functional theory
corey-chaykovsky reaction
catalytic asymmetric aziridination
polarizable continuum model
stereoselective-synthesis
n-sulfonylimines
enantioselective aziridination
stereocontrolled synthesis
thermodynamic preference
regioselective-synthesis
aziridination
density functional calculations
diastereoselectivity
reaction mechanisms
ylides
 
Description Mechanism and diastereoselectivity of sulfur ylide promoted aziridination reactions were studied by density functional theory with inclusion of solvent effects through the continuum solvation model. The general reaction pathway was modeled for the addition of substituted sulfur ylides (Me2S+ CH-R) to an aldimine ((E)-methyl ethylidenecarbamate, MeHC=NCO2Me). The nature of the substituents on the ylidic carbon atom substantially affects the reaction profile. The stabilized (R=COMe) and semistabilized (R=Ph) ylides follow a cisoid addition mode leading to trans aziridines via anti betaine intermediates. The simplest model ylide (unstabilized, R=H) underwent cisoid addition in a similar fashion. In the case of stabilized ylides product diastereoselectivity is controlled by the barriers of the elimination step leading to the 2,3-trans aziridine, whereas it is decided in the addition step in the case of semistabilized ylides. The importance of steric and electronic factors in diastereoselective addition (2 and 5) and elimination (5) transition states was established. Comparison of results obtained with the gas-phase optimized geometries and with the fully optimized solvent-phase geometries reveals that the inclusion of solvent effects does not bring about any dramatic changes in the reaction profiles for all three kinds of ylides. In particular, diastereoselectivity for both kinds of ylides was found to be nearly the same in both these approaches.
 
Publisher WILEY-V C H VERLAG GMBH
 
Date 2011-09-01T15:07:55Z
2011-12-26T12:59:42Z
2011-12-27T05:52:22Z
2011-09-01T15:07:55Z
2011-12-26T12:59:42Z
2011-12-27T05:52:22Z
2007
 
Type Article
 
Identifier CHEMISTRY-A EUROPEAN JOURNAL, 13(17), 4805-4815
0947-6539
http://dx.doi.org/10.1002/chem.200700303
http://dspace.library.iitb.ac.in/xmlui/handle/10054/12807
http://hdl.handle.net/10054/12807
 
Language en