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Face-selective diels-alder reactions between unsymmetrical cyclohexadienes and symmetric trans-dienophile: an experimental and computational investigation

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Title Face-selective diels-alder reactions between unsymmetrical cyclohexadienes and symmetric trans-dienophile: an experimental and computational investigation
 
Creator LAHIRI, S
YADAV, S
BANERJEE, S
PATIL, MP
SUNOJ, RB
 
Subject secondary orbital interactions
density-functional theory
ab-initio
danishefskys diene
endo/exo selectivity
facial stereoselectivity
cycloaddition reactions
pentadienyl acrylates
maleic-anhydride
state geometries
 
Description [GRAPHICS] A combined experimental and theoretical study of the Diels-Alder reactions between 2-trimethylsiloxy-1,3-cyclohexadiene (2-11) and (E)-1,4-diphenylbut-2-ene-1,4-dione (1) is reported. Two diastercomeric products, 5-endo-6-exo- (nx) and 5-exo-6-endo- (xn) dibenzoyl derivatives, are possible with symmetric trans-dienophile (1). While in many cases 5-endo-6-exo product is preferred over the corresponding 5-exo-6-endo product, the product ratio nx:xn is found to vary with the position of substituents on the diene. The density functional theory studies with the mPWIPW91/6-31G* as well as the 133LYP/631G* levels reveal that the electrostatic repulsion between the oxygen lone pairs on the diene and the dienophile is critical to the observed product selectivities. The optimized transition state geometries though appeared to involve secondary orbital interactions, careful examination of the frontier Kohn-Sharn orbitals as well as calculations with the natural bond orbital (NBO) analyses confirm the absence of SOI in these transition states. In the case of methyl-substituted dienes, a cumulative effect of steric and electrostatic interactions between the diene and the dienophile is found to be the controlling element toward the observed selectivity.
 
Publisher AMER CHEMICAL SOC
 
Date 2011-10-15T07:01:41Z
2011-12-15T09:16:23Z
2011-10-15T07:01:41Z
2011-12-15T09:16:23Z
2008
 
Type Review
 
Identifier JOURNAL OF ORGANIC CHEMISTRY,73(2)435-444
0022-3263
http://dx.doi.org/10.1021/jo701884d
http://dspace.library.iitb.ac.in/xmlui/handle/10054/13942
http://hdl.handle.net/100/3135
 
Language en