可以 (pi) 6 + (pi) 4 = 10? 探索向高度不和的10个成员环的循环加法路径
Roger W Alder1, Jeremy N Harvey, Guy C Lloyd-Jones
1School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK. rog.alder@bristol.ac.uk
Journal of the American Chemical Society
|June 1, 2010
概括
本研究探讨了合成10个环的6pi + 4pi循环加法,发现它们可以用替代剂来克服重新排列问题. 这些反应为新的不和循环系统和双循环结构提供了途径.
科学领域:
- 有机化学 有机化学
- 计算化学计算化学
- 合成化学 合成化学
背景情况:
- 在有机化学中,研究中型环的新型合成路径至关重要.
- 了解 (pi) 6 + (pi) 4循环添加的可行性,以构建10个成员的环是关键.
- 探索各种不和系统为新的分子架构提供了潜力.
研究的目的:
- 通过 (pi) 6 + (pi) 4 循环加法来确定形成无桥梁的 10 个环的可行性.
- 为了确定这些循环添加反应的潜在合成挑战和解决方案.
- 预测新型,高度不和的循环化合物的形成.
主要方法:
- 使用密度函数理论 (DFT) 的计算.
- G3 ((MP2) 计算用于评估反应能量和障碍物.
- 探索各种6pi和4pi二烯和二烯系统.
主要成果:
- 确定了30种外热 (pi) 6 + (pi) 4循环添加物.
- 发现产品的拉伸能量与循环甲相比.
- 竞争反应和应对重组是主要障碍,但替代剂可以减轻这些障碍.
- 具体条件 (例如,使用 (E) - hexa-1,3,5-triene) 和结构锁定衍生品显示出有希望.
- 预测至少11个新型不和循环系统的合成.
结论:
- 无的10个环可以通过 (pi) 6 + (pi) 4循环加法来合成.
- 替代物效应和反应物立体化学对于成功合成至关重要.
- 这些反应可以进入多样化,高度不和的循环和双循环结构.
- 复杂分子的立体控制合成的潜力.
相关概念视频
Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
Frost Circles for Different Conjugated Systems
The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
Stereoisomerism of Cyclic Compounds
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...

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