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submitted on 19.12.2019 and posted on 23.12.2019by Veejendra Yadav, Dasari L V K Prasad, Arpita Yadav, Kedar Yadav
quantum chemical calculations, the Diels-Alder cycloaddition reaction of maleic
anhydride with furan favors the endo-isomer kinetically in the gas phase. This
preference, however, changes in favor of the exo-isomer on inclusion of solvent
effects. For example, in acetonitrile, the exo-isomer was calculated to form twice
as fast as the endo-isomer at room temperature, an observation that corroborates
well with the experiments. The free energy change of the reaction is such that
it allows faster reversal of the endo-isomer to the reactants in an equilibrium
process and, thus, the predominance of the more stable exo-isomer eventually.
The reaction of maleimide with furan is similar to that of maleic anhydride. However,
it favors predominantly endo selectivity at temperatures below 320 K which is
in excellent agreement with the experimental studies of temperature dependence of
this DA reaction. Further, a gedanken calculation of the DA reaction of
cyclopropene with furan has been investigated to delineate the effect of the retro-pathway
on the stereoselectivity.