Pseudohelical and Helical Primary Structures of 1,2-Spiroannelated Four- and Five-Membered Rings: Syntheses and Chiroptical Properties
作者:Tien Widjaja、Lutz Fitjer、Aritra Pal、Hans-Georg Schmidt、Mathias Noltemeyer、Christian Diedrich、Stefan Grimme
DOI:10.1021/jo7017558
日期:2007.11.1
The pseudohelical hydrocarbons (R)-6, (S)-7, and (R)-8 and the helical hydrocarbon (P)-9, formally derived from the helical hydrocarbon (P)-4 by stepwise replacement of each of the four-membered rings by a five-membered ring, have been prepared. Their optical rotations vary systematically, both in magnitude and sign. Of the extremes, (P)-4 represents the usual case of a right-handed dextrorotatory
伪螺旋烃(R)-6,(S)-7和(R)-8和螺旋烃(P)-9是通过逐步置换四种烃的形式正式衍生自螺旋烃(P)-4的五元环的五元环已经准备好了。它们的旋光度在大小和符号上都有系统的变化。在极端情况下,(P)-4代表右旋右旋螺旋的通常情况,而(P)-9代表代表右旋左旋螺旋的异常情况。为了使这些事实合理化,DFT计算了(P的旋转功率)已完成三元,四元和五元环的螺旋。结果表明,三元环的刚性螺旋与实验数据非常吻合,并且始终显示四元和五元环的柔性螺旋的正确符号和量级,Boltzmann平均旋光度为最多必须使用六个conformer。在后者的共形体中,内球键的一组大二面角对应于高的比旋度,而一组小二面角对应于低的比旋度。结果,玻尔兹曼平均值明显取决于所涉及的构象异构体的几何形状和重量。