Notable Effect of an Electron-Withdrawing Group at C3 on the Selective Formation of Alkylidenecyclobutanes in the Thermal Denitrogenation of 4-Spirocyclopropane-1-pyrazolines. Nonstatistical Dynamics Effects in the Denitrogenation Reactions
observed for the denitrogenation of 6 and 10a. The contradiction between the experimental and standard computational results was solved by considering nonstatistical dynamics effects in the concerted denitrogenation reactions. Although the energy minimum pathway from the transitionstates of the concerted denitrogenation of the 3-carboalkoxy-substituted 1-pyrazolines involves generation of the corresponding