Through-space interactions of double bonds by photoelectron spectroscopy
作者:Joseph B. Lambert、Liang. Xue、Richard J. Bosch、Kalulu M. Taba、Dale E. Marko、Shigeyuki. Urano、Pierre R. LeBreton
DOI:10.1021/ja00284a022
日期:1986.11
to the exocyclic doublebond. The NMR, UPS, and ab initio results provide an initial understanding of the three dimensionality of the n-electron steric effects. Nuclear magnetic resonance studies have shown that the doublebond interacts in a complex fashion with remote polar substituents.,-* A 3-axial substituent in a six-membered ring is more repulsive with an exocyclic doublebond than with a saturated
双键和远程极性取代基之间的空间效应,以前在核磁共振 (NMR) 光谱中表现出来,在紫外光电子光谱 (UPS) 中也很明显。通过缩醛基团(二甲基和亚乙基)在外型亚甲基环己烷的 3 轴位置引入醚官能团。3-轴醚基团通过空间相互作用使双键上的 7r 轨道不稳定 0.1-0.2 eV(3-赤道醚基团本身几乎没有影响或没有影响)。这种相互作用显然是 NMR 光谱观察到的 3-轴甲氧基比例降低的原因。相比之下,环己烯中的 4-轴醚官能团通过键电子撤回显示出 n 轨道的轻微稳定。这些结果也与核磁共振观察一致,因为环己烯的环内双键允许更大比例的 4-轴甲氧基。Ab initio 计算通过平行观察到的 r 轨道能量和提供电子密度来支持观察。尽管 3-轴甲氧基明显极化亚甲基环己烷中的双键,但 4-轴甲氧基对环己烯的电子密度几乎没有影响或没有影响,即使甲氧基更接近环内双键而不是环外双键。NMR、UPS 和 ab
Acid-Catalyzed Cyclization of Epoxyallylsilanes. An Unusual Rearrangement Cyclization Process
作者:Asunción Barbero、Pilar Castreño、Francisco J. Pulido
DOI:10.1021/ol035297v
日期:2003.10.1
synthesis of epoxyallylsilanes bearing the phenyldimethylsilyl group is reported that involves silylcupration of allene, conjugate addition to enones, and sulfur-ylide-mediated epoxidation. The Lewis acid-catalyzed cyclization of these substrates is presented. The expected normal products derived from 5-exo and/or 6-endo attack are not observed; instead, methylenecyclohexanols resulting from a tandem rea
Mechanistic Variations in Ionic Hydrogenation of Unsaturated Phosphine and Amine Boranes
作者:Timothy S. De Vries、Supriyo Majumder、Angela M. Sandelin、Guoqiang Wang、Edwin Vedejs
DOI:10.1021/ol2031203
日期:2012.2.3
Internal hydride transfer occurs when tethered carbocations are generated from unsaturated phosphine or phosphinite boranes. 3-Methylenecyclohexyl-derived boranes 12 or 18 react with MsOH to give ionic hydrogenation products with high syn-selectivity. With unsaturated amineboranes, initial hydrogen evolution gives BH2(OMs) complexes, but IH occurs using excess MsOH in a slower second stage. A diastereoselective
Synthesis of 3-Methylenecyclohexan-1-ols by Lewis Acid Catalyzed Cyclization of (Epoxy-allyl)silanes
作者:Francisco J. Pulido、Asunción Barbero、Pilar Castreño
DOI:10.1002/ejoc.200901263
日期:2010.3
A newroute for the synthesis of (epoxy-allyl)silanes bearing the PhMe 2 Si group has been developed and their acid-catalyzed cyclization studied. The so-called normal products derived from 5-exo or 6-endo attack were never obtained. On the contrary, an interesting tandem rearrangement/cyclization process was observed, which selectively led to 3-methylenecyclohexan-1-ols. A mechanism is proposed to
已经开发了一种合成带有 PhMe 2 Si 基团的(环氧-烯丙基)硅烷的新途径,并研究了它们的酸催化环化。5-exo 或 6-endo 攻击衍生的所谓正常产物从未得到过。相反,观察到了一个有趣的串联重排/环化过程,它选择性地产生了 3-亚甲基环己-1-醇。提出了一种机制来解释这种串联反应。环化过程的立体选择性取决于催化剂的性质。
Scope and limitations of the stereoselective homogeneous hydrogenation of methylenecyclohexanols by cationic rhodium complexes
作者:John M. Brown、Stephen A. Hall
DOI:10.1016/s0040-4039(01)80167-2
日期:1984.1
Homogeneous catalytic hydrogenation of 3-methylenecyclohexanol gives -3-methylcyclohexanol with 98% stereoselectivity. but low selectivity is observed for 2-methylenecyclohexanol and 2-methylenecyclohexanemethanol.