四同芳香性转烯及其羰基硼衍生物

Tetrahomoaromatic Hypostrophene and Its BCO-analogues

运用G03W程序,在高精度理论水平(B3P86/6-311+G**)下,对母体转烯(Hypostrophene)及其BCO衍生物的单态、三态、开壳层单态的Cope重排体系进行了理论研究:对体系进行了相应的结构优化和频率计算,并进一步计算了体系的重排势垒、反应能量、核独立化学位移值等理论参数.文中首次提出具有四同芳香性的实例:转烯的Cope重排过渡态.计算同时表明BCO取代CH的行为使得进行Cope重排的反应物和过渡态的离域性、芳香性以及稳定性都得到很大的促进,这可以从前线轨道的成键以及延伸方面得到合理的解释.所得结果进一步验证了BCO基团的稳定性效应.

Calculations on the normal singlet, triplet and open-shell singlet of hypostrophene, its BCO-analogues and the theoretical transition states for the Cope rearrangement at the B3P86/6-311 ＋G^＊＊ level have been done with G03W program. By discussing the geometries of the hypostrophene and its BCO-analogues, nucleus independent chemical shifts （NICS）, the Cope barriers and the molecule orbitals, we got some interesting information. The transition state for the hypostrophene was the first neutral tetrahomoaromaticity case in recent papers. In the hypostrophene system, the replacements of CH by BCO caused theoretical transition states to be delocalized and aromatic energy minimized, resulting in enhancement of delocalization, aromaticity and stability of both reactants and transition states, which confirmed the BCO stabilization effects further.