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Density functional theory investigations on sulfur ylide promoted cyclopropanation reactions: insights on mechanism and diastereoselection issues

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Title Density functional theory investigations on sulfur ylide promoted cyclopropanation reactions: insights on mechanism and diastereoselection issues
 
Creator JANARDANAN, D
SUNOJ, RB
 
Subject polarizable continuum model
p-tolyl sulfoxide
catalytic asymmetric cyclopropanation
highly enantioselective synthesis
stabilized sulfonium ylids
tandem oxidation processes
amino-acids
stereoselective cyclopropanation
alpha,beta-unsaturated esters
mediated cyclopropanation
 
Description [graphics] The mechanism and diastereoselectivity of synthetically useful sulfur ylide promoted cyclopropanation reactions have been studied using the density functional theory method. Addition of different substituted ylides (Me2S+CH-R) to enone ((E)-pent-3-en-2-one, MeHCCH-COMe) has been investigated. The nature of the substituent on the ylidic carbon brings about subtle changes in the reaction profile. The stabilized (R = COMe) and semistabilized (R = Ph) ylides follow a cisoid addition mode, leading to 1,2-trans and 1,2-cis cyclopropanes, respectively, via syn and anti betaine intermediates. The simplest and highly reactive model ylide (R = H) prefers a transoid addition mode. Diastereoselectivity is controlled by the barrier for cisoid-transoid rotation in the case of stabilized ylides, whereas the initial electrophilic addition is found to be the diastereoselectivity-determining step for semistabilized ylides. High selectivity toward trans cyclopropanes with stabilized ylides are predicted on the basis of the relative activation energies of diastereomeric torsional transition states. The energy differences between these transition states could be rationalized with the help of weak intramolecular as well as other stereoelectronic interactions.
 
Publisher AMER CHEMICAL SOC
 
Date 2011-10-14T12:29:57Z
2011-12-15T09:16:22Z
2011-10-14T12:29:57Z
2011-12-15T09:16:22Z
2007
 
Type Review
 
Identifier JOURNAL OF ORGANIC CHEMISTRY,72(2)331-341
0022-3263
http://dx.doi.org/10.1021/jo061198u
http://dspace.library.iitb.ac.in/xmlui/handle/10054/13924
http://hdl.handle.net/100/3129
 
Language en