School of Engineering and Physical Sciences, Chemistry - William H. Perkin Building, Heriot-Watt University, Edinburgh EH14 4AS, UK.
Org Biomol Chem. 2012 Jun 14;10(22):4433-40. doi: 10.1039/c2ob25183c. Epub 2012 May 4.
Density functional theory calculations have been employed to investigate the mechanism of gold(I)-catalysed rearrangements of cyclopropenes. Product formation is controlled by the initial ring-opening step which results in the formation of a gold-stabilised carbocation/gold carbene intermediate. With 3-phenylcyclopropene-3-methylcarboxylate, the preferred intermediate allows cyclisation via nucleophilic attack of the carbonyl group and hence butenolide formation. Further calculations on simple model systems show that substituent effects can be rationalised by the charge distribution in the ring-opening transition state and, in particular, a loss of negative charge at what becomes the β-position of the intermediate. With 1-C(3)H(3)R cyclopropenes (R = Me, vinyl, Ph), ring-opening therefore places the substituent at the β-position.
密度泛函理论计算被用来研究环丙烯的金（I）催化重排反应的机理。产物的形成受到初始开环步骤的控制，该步骤导致形成金稳定的碳阳离子/金卡宾中间体。对于 3-苯基环丙基-3-甲酯，首选的中间体允许通过羰基的亲核攻击进行环化，从而形成丁烯内酯。对简单模型体系的进一步计算表明，取代基效应可以通过开环过渡态中的电荷分布来合理化，特别是在中间体的β位失去负电荷。对于 1-C(3)H(3)R 环丙烯（R = Me、vinyl、Ph），开环因此将取代基置于β位。
