Kyne Sara H, Schiesser Carl H, Matsubara Hiroshi
School of Chemistry, The University of Melbourne, Victoria, Australia 3010.
Org Biomol Chem. 2007 Dec 21;5(24):3938-43. doi: 10.1039/b714324a. Epub 2007 Nov 2.
Ab initio and DFT calculations reveal that oxyacyl radicals add to imines and electron-rich olefins through simultaneous SOMO-pi*, SOMO-pi and pi*-HOMO interactions between the radical and the radicalophile. At the BHandHLYP/aug-cc-pVDZ level, energy barriers of 20.3 and 22.0 kJ mol(-1) are calculated for the attack of methoxycarbonyl radical at the carbon and nitrogen ends of methanimine, respectively. In comparison, barriers of 22.0 and 8.6 kJ mol(-1) are calculated at BHandHLYP/aug-cc-pVDZ for reaction of methoxycarbonyl radical at the 1- and 2-positions in aminoethylene, respectively. Natural bond orbital (NBO) analysis at the BHandHLYP/6-311G** level of theory reveals that SOMO-pi*, SOMO-pi and pi*-LP interactions are worth 111, 394 and 55 kJ mol(-1) respectively in the transition state (8) for reaction of oxyacyl radical at the nitrogen end of methanimine; similar interactions are observed for the chemistry involving aminoethylene. These multi-component interactions are responsible for the unusual motion vectors associated with the transition states involved in these reactions.
从头算和密度泛函理论（DFT）计算表明，酰氧基自由基通过自由基与亲自由基试剂之间同时发生的单占据分子轨道-反键分子轨道（SOMO-π*）、单占据分子轨道-成键分子轨道（SOMO-π）和成键分子轨道-最高占据分子轨道（π*-HOMO）相互作用，加成到亚胺和富电子烯烃上。在BHandHLYP/aug-cc-pVDZ水平下，计算出甲氧基羰基自由基进攻亚甲基亚胺的碳端和氮端时的能垒分别为20.3和22.0 kJ·mol⁻¹。相比之下，在BHandHLYP/aug-cc-pVDZ水平下，计算出甲氧基羰基自由基与氨基乙烯中1位和2位反应的能垒分别为22.0和8.6 kJ·mol⁻¹。在BHandHLYP/6-311G理论水平下的自然键轨道（NBO）分析表明，在亚甲基亚胺氮端的酰氧基自由基反应的过渡态（8）中，SOMO-π、SOMO-π和π-孤对电子（LP）相互作用分别贡献111、394和55 kJ·mol⁻¹；对于涉及氨基乙烯的化学反应也观察到类似的相互作用。这些多组分相互作用导致了与这些反应所涉及的过渡态相关的异常运动矢量。
