Excited- and Ground-State Versions of the Tri-π-methane Rearrangement: Mechanistic and Exploratory Organic Photochemistry<sup>1</sup>
作者:Howard E. Zimmerman、Vladimír Církva
DOI:10.1021/jo001601b
日期:2001.3.1
Since both three-ring and five-ring photoproducts often are found to be produced, it was important to establish that the observed photochemistry was really the result of a true single-step tri-pi-methane rearrangement and not the consequence of two sequential rearrangements, first to form a vinyl cyclopropane which subsequently ring expanded to the cyclopentene. The general situation has three species-A
现在已经很好地确定了具有两个连接到单个碳上的可导致pi取代的环丙烷的pi-基的di-pi-甲烷重排。本研究的目标是探索具有三个pi部分与sp(3)杂化原子连接的pi系统的分子系统,以寻求三pi-甲烷重排。实际上,已发现此类系统确实进行了光化学重排以提供环戊烯。然而,还确定了在直接辐射下乙烯基环丙烷环膨胀成环戊烯。由于经常发现同时产生三环和五环光产物,因此重要的是要确定观察到的光化学确实是真正的单步三-pi-甲烷重排的结果,而不是两次连续重排的结果,首先形成乙烯基环丙烷,然后环膨胀成环戊烯。一般情况下,对应于三-pi-甲烷反应物A,乙烯基环丙烷光产物B和环戊烯光产物C的物质分别为A,B和C三种。涉及三个速率常数,即A-> B的k(1),对于A-> C,k(2);对于B-> C,k(3)。将动力学应用于两个示例,并提供了避免差异光吸收的规定。利用单线敏化。已经确定,环戊烯光产物的直接形成比环扩