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Diels–Alder Reactions of Symmetrically 1,4‐Disubstituted Dienes: Theoretical Study on the Influence of the Configuration of the Double Bonds on the Regio‐ and Endoselectivity
Author(s) -
Baki Samira,
Maddaluno Jacques,
Derdour Aïcha,
Chaquin Patrick
Publication year - 2008
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200701082
Subject(s) - chemistry , regioselectivity , stereocenter , double bond , steric effects , reactivity (psychology) , diene , computational chemistry , stereochemistry , ethylene , selectivity , transition state , organic chemistry , catalysis , medicine , natural rubber , alternative medicine , pathology , enantioselective synthesis
Abstract It was experimentally shown in Diels‐Alder reactions that symmetrically 1,4‐disubstituted dienes exhibit high regio‐ and endoselectivity induced by the ( E , Z ) configuration of the double bonds. In order to understand the origin of this selectivity, the transition states associated with the reaction between a series of such dienes (R = OMe, CH 3 , NH 2 , F, CN) on substituted ethylene (R′ = CO 2 Me, CN, F, OMe) were determined by DFT calculations. If the regioselectivity confirmed by a single‐point MP2 calculation is predicted to be good in most cases, its direction remains difficult to predict; the R′ group of the dienophile can orient itself toward either the ( Z ) or the ( E ) side of the diene. Neither primary nor secondary frontier orbital interactions appear to be able to rationalize these results. They are more likely explained by a delicate balance between steric and electrostatic interactions. This hypothesis is further supported by the calculated reactivity of the ( E , E ) and ( Z , Z ) corresponding dienes. In any case, a standard DFT calculation, confirmed by a single‐point MP2 step, is likely to provide a reliable guideline for a synthesis strategy that allows the control of up to four stereogenic centres in a single reaction step.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)