✍ Scribed by Branko S. Jursic; Zoran Zdravkovski
No coin nor oath required. For personal study only.
PM3 calculations of the pull-push dienes in the Diels-Alder reactions with acetonitrile and acrylonitrile are presented. Two of the pull-push dienes, Idimethylamino-I -iodoisoprene and I -fluoro-I -dimethylaminoisoprene where studied. In the iodo isomer the C-Z bond can be easily broken and the actual species considered in the calculation is the corresponding cation 3. Frontier orbitals and the energy barriers in the reactions were considered for all possible cases in the two step, as well as in the concerted mechanism. The frontier orbital calculations of the reactants correctly predict the products of the reactions. According to the calculated energy barriers for the CN addition of acrylonitrile to cation 3 the two step addition is preferred over the concerted mechanism. In the case of the Diels-Alder reaction of fluoroisoprene and acrylonitrile the concerted mechanism was favored. The PM3 energy barriers of all possible cases suggest that in the endo acrylonitrile addition, the CC double bond rather than the CN triple bond is added to the diene. The predicted PM3 products of the reactions are in full agreement with ones obtained experimentally.
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