Preparation, structural properties and thermal isomerization of hex-3-ene-1,5-diyne bridged [2.2]paracyclophanes.
Preparation, structural properties and thermal isomerization of hex-3-ene-1,5-diyne bridged [2.2]paracyclophanes.
复制标题
己-3-烯-1,5-二炔桥联[2.2]对环芳烷的制备、结构性质和热异构化。
作者：
I. Dix;L. Bondarenko;P. Jones;L. Ernst;K. Ibrom;J. Grunenberg;R. Boese;H. Hopf
[2.2]对环芳烷部分用作连接己-3-烯-1，5-二炔单元末端的间隔基，这是一种π-系统，在热交换器上通常环芳构化为苯环（Bergman环化）。为了制备假偕桥连体系9，将二乙炔3扩链成二醇16，其在转化成假偕二溴化物17后通过用LiHMDS/HMPA处理闭环成[2.2]对环芳烷烯二炔9。假邻位双醛24的McMurry偶联导致形成己二烯炔桥连的环蕃27，而假邻位桥连的烃11是通过首先由24制备二醇28，将后者转化成二氧戊环29，在最后一步中通过用Tf 2 O/EtN（iPr）2处理得到烯烃11而得到的。假宝石桥连己烯二炔9的真实Bergman产物10通过常规顺序从乙炔基甲酰基底物18开始合成。由于假邻位烯二炔桥连烃11是热不稳定的，因此制备其苯并稠合衍生物34。没有经典的Bergman环化反应，可以观察到任何的[2.2] paracyclophane桥连己烯二炔在这里制备。在假宝石系列的富烯14和15是唯一的产品，可以确定在热条件下（麦克默里耦合）; benzannelated基板34得到苯并富烯桥环蕃36光解。伯格曼环化反应产生富烯衍生物是极其罕见的。用柔顺常数讨论了9和34的环化反应机理。在这项研究中合成的烃的结构归属是基于光谱研究以及9，10，11，27和34的X-射线结构分析。
The [2.2]paracyclophane moiety is used as a spacer to connect the ends of a hex-3-ene-1,5-diyne unit, a π-system that on thermolysis usually cycloaromatizes to a benzene ring (Bergman cyclization). For the preparation of the pseudo-geminally-bridged system 9, the diacetylene 3 was chain-extended to the diol 16, which after conversion to the pseudo-geminal dibromide 17 was ring-closed by treatment with LiHMDS/HMPA to the [2.2]paracyclophane enediyne 9. Whereas the McMurry coupling of the pseudo-ortho bisaldehyde 24 resulted in the formation of the hexadienyne-bridged cyclophane 27, the pseudo-ortho-bridged hydrocarbon 11 was obtained by preparing first the diol 28 from 24, converting the latter into the dioxolane 29, which in the last step furnished the olefin 11 by treatment with Tf2 O/EtN(iPr)2 . The authentic Bergman product 10 of the pseudo-gem-bridged hexenediyne 9 was synthesized by a conventional sequence starting from the ethynyl formyl substrate 18. Since the pseudo-ortho-enediyne-bridged hydrocarbon 11 is thermally labile, its benzannelated derivate 34 was prepared. No classical Bergman cyclization reactions could be observed for any of the [2.2]paracyclophane-bridged hexenediynes prepared here. In the pseudo-gem-series the fulvenes 14 and 15 were the only products that could be identified under thermal conditions (McMurry coupling); the benzannelated substrate 34 gave the benzofulvene-bridged cyclophane 36 on photolysis. Bergman cyclizations yielding fulvene derivatives are extremely rare. The mechanism of the cyclization of 9 and 34 is discussed, using compliance constants. The structure assignments of the hydrocarbons synthesized in this study are based on spectroscopic studies as well as X-ray structural analyses for 9, 10, 11, 27, and 34.