作者:Xavier Creary、Andrea Losch、William Sullivan
DOI:10.1021/jo071114x
日期:2007.10.1
rearrangements occur via the (n,π*) triplet state, which fragments the strained cyclopropane bond. Intersystem crossing followed by ring closure gives the observed products. No photoreduction is seen in i-PrOH. Potential Norrish type II processes are also bypassed. It is suggested that the cyclopropane bond fragmentation dissipates the triplet energy and that the new intermediates are not energetic enough
当用350 nm的光照射时,某些含有羰基取代基的1,1-二甲基-2-芳基-3-亚甲基环丙烷会发生重排。这些重排通过(n,π*)三重态发生,该三重态分裂了应变的环丙烷键。系统间相交,然后环闭合,得到观察到的产物。没有光还原被认为是在我-PrOH 潜在的Norrish II型流程也被绕过了。建议环丙烷键断裂会耗散三重态能量,并且新的中间体的能量不足以分子内方式或从溶剂中提取氢原子。硝基取代的系统会经历类似的光引发重排。萘,联苯,苯乙烯和苯乙炔类似物的苯甲酮敏化也可能导致重排,大概是通过三重态的敏化产生。当三重态不能通过直接辐射或敏化过程获得时,不会发生亚甲基环丙烷重排。二茂铁基类似物是一个例外,它不进行光重排,这可能是由于三重态中间体的寿命很短。