Theoretical studies on the Bergman cyclizations of the enediyne and its N-substituted analogs
We have studied the Bergman cyclizations of the enediyne and its four N-substituted analogues [(Z)-pent-2-en-4-ynenitrile, 3-azahex-3-en-1,5-diyne, malenotrile, and 3,4-azahex-3-en-1,5-diyne] using the complete active space self-consistent field and multi-configurational second-order perturbation theory methods in conjunction with the atomic natural orbital basis sets. On the basis of our calculations, we concluded that the replacements of the terminal C atom(s) or the middle C atom(s) in the C=C bond by the N atom(s) increase or decrease the energy barrier values, respectively. And there exist stable ring biradical products on the T1 potential energy surfaces for the all reactions. However, on the S0 potential energy surfaces the ring biradical products exist only for the reactions of enediyne, (Z)-pent-2-en-4-ynenitrile, and 3-azahex-3-en-1,5-diyne.
The detailed results have been published in Journal of Computational Chemistry ( Hua Dong, Bo-Zhen Chen,* Ming-Bao Huang, and Roland Lindh, Journal of Computational Chemistry, 2012, 33, 537–549.)