The Cubane Cage – A Sensitive Probe for Assessing Substituent Effects on a Four-Membered Ring, Part II
作者:Hermann Irngartinger、Stefan Strack、Frank Gredel、Andreas Dreuw、Ernest W. Della
DOI:10.1002/(sici)1099-0690(199905)1999:5<1253::aid-ejoc1253>3.0.co;2-m
日期:1999.5
found to depend on the orientation. The cage bond antiperiplanar to the methyl group is shortened, while the cage bonds in gauche orientation to this group are lengthened. As seen in the case of the halogen-substituted derivatives, the bonds bearing the acetoxy substituent are shortened due to the σ-acceptor property of this group. Ab initio calculations on compounds 1, 2, 4, and 5 performed at the 6-31G*
4-甲氧基立方烷-1-羧酸甲酯 (1), 1-乙酰氨基-4-氟立方烷 (2), 4-乙酰氧基立方烷-1-羧酸甲酯 (3), 1,4-二氟立方烷 (4), 1, 的晶体结构4-二氯立方烷 (5) 和 N,N-二异丙基立方烷-1,4-二甲酰胺 (6) 已通过 X 射线衍射分析进行了研究。氟和氯取代基会导致连键缩短,如 4-haloccubane-1-carboxylates 中所见。笼键与酯取代基相邻,在该基团的 π 受体影响方面具有有利的取向,变得比 CH-CH 键长。此外,已经通过实验研究了该基团相对于立方烷骨架内的键的取向对键长的影响。还发现甲氧基的影响取决于取向。与甲基基团反面的笼键缩短,而与该基团呈gauche 方向的笼键加长。正如在卤素取代衍生物的情况下所见,由于该基团的 σ 受体性质,带有乙酰氧基取代基的键被缩短。在 6-31G* 水平下对化合物 1、2、4 和 5 进行的从头算计算证实了实验结果。