Department of Chemistry, University of Idaho , 875 Perimeter Drive, Mail Stop 2343, Moscow, Idaho 83844-2343, United States.
J Org Chem. 2017 Apr 21;82(8):4136-4147. doi: 10.1021/acs.joc.7b00043. Epub 2017 Apr 11.
The low activation barrier to the Cope rearrangement of semibullvalenes has been attributed to the inherent ring-strain of this nucleus. Appropriate, Dewar-Hoffmann, substitution of semibullvalene results in the stabilization of the transition state and a further lowering of the Cope barrier. An alternative proposal for lowering/eliminating this barrier is the use of strain to destabilize the localized semibullvalene. Using density functional and Hartree-Fock calculations, we predict that additionally straining the semibullvalene nucleus, by small ring annelations, will lead to a lowering of the Cope barrier and ultimately to ground state neutral homoaromatics.
半环辛二烯的 Cope 重排的低活化势垒归因于该核的固有环张力。适当的 Dewar-Hoffmann 取代半环辛二烯导致过渡态稳定，并进一步降低 Cope 势垒。降低/消除该势垒的另一种方法是利用应变使局部半环辛二烯失稳。使用密度泛函和 Hartree-Fock 计算，我们预测通过小环稠合进一步应变半环辛二烯核，将导致 Cope 势垒降低，并最终导致基态中性同芳香烃。
