Braña Pedro, Gimeno José, Sordo José A
Laboratorio de Química Computacional, Instituto de Química Organometálica Enrique Moles (Unidad asociada al CSIC), Facultad de Química, Universidad de Oviedo, Julián Clavería 8, 33006, Oviedo, Principado de Asturias, Spain.
J Org Chem. 2004 Apr 2;69(7):2544-50. doi: 10.1021/jo035346h.
A theoretical analysis allows for the rationalization of the recently reported unusual formation under mild conditions of a cyclobutylidene ring from a diastereoselective [2 + 2] intramolecular cycloaddition of two C=C systems. The reaction takes place by heating in dichloromethane the vinylidene complexes [Ru((eta(5),eta(3)-C(9)H(7))[=C=C(R)H]kappa(1)-(P)-PPh(2)(C(3)H(5))][BF(4)] (R = Ph, p-Me-C(6)H(4)) (1) yielding the bicyclic alkylidene complexes [Ru((eta(5),eta(3)-C(9)H(7))kappa(2)-(P,C)-(=CC(R)HCH(2)CHCH(2)-PPh(2)][BF(4)] (2). The proposed mechanism represents an alternative to the classical Woodward-Hoffmann's supra-antara approach.
理论分析使得近期报道的在温和条件下通过两个碳碳双键的非对映选择性分子内[2 + 2]环加成形成环丁叉环这一异常反应得以合理化。该反应是通过在二氯甲烷中加热亚乙烯基配合物[Ru((η⁵,η³-C₉H₇)[=C=C(R)H]κ¹-(P)-PPh₂(C₃H₅)][BF₄]（R = Ph，对甲基苯基）（1）进行的，生成双环亚烷基配合物[Ru((η⁵,η³-C₉H₇)κ²-(P,C)-(=CC(R)HCH₂CHCH₂-PPh₂][BF₄]（2）。所提出的机理代表了经典伍德沃德 - 霍夫曼的超 - antar方法的一种替代方案。
