Photochemical generation of stable o-xylylene derivatives by the electrocyclic ring opening of some polycyclic benzocyclobutene derivatives
Photochemical generation of stable o-xylylene derivatives by the electrocyclic ring opening of some polycyclic benzocyclobutene derivatives
复制标题
通过一些多环苯并环丁烯衍生物的电环开环光化学生成稳定的邻二甲苯衍生物
DOI：
10.1021/ja00442a032
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发表时间：
1976
影响因子：
15
通讯作者：
J. Michl
中科院分区：
文献类型：
--
作者：
Robert D. Miller;J. Kolc;J. Michl
通过在3-甲基戊烷玻璃（77 K）中辐照多环苯并环丁烯2b、3b和12，生成了在室温和无氧条件下在流体溶液中稳定的邻苯二甲撑1的简单取代衍生物。光化学开环需要刚性介质，并且可能涉及起始材料对两个光子的连续吸收。5 b的紫外和发射光谱的相似性，其中发色团被限制为共面性，与母体邻二甲苯1的相似性表明1接近于平面。CA的常规振动级数。在5 b的吸收光谱中看到的1500 cm-1表明在激发态中C= C键的长度普遍增加。虽然5 b在室温下静置时没有热再闭合的趋势，但在刚性介质或流体溶液中以350 nm照射导致快速非立体特异性再闭合以再生苯并环丁烯衍生物2b和3b。
Simple substituted derivatives of o-xylylene 1 which are stable and characterizable in fluid solution at room temper-ature in the absence of oxygen are generated by the irradiation of the polycyclic benzocyclobutenes 2b, 3b, and 12 in 3-methylpentane glass (77 K). The photochemical ring opening requires rigid media and may involve a successive absorption of two photons by the starting materials. The similarity of the UV and emission spectra of 5b, inwhich the chromophore is restricted to coplanarity, with those of the parent o-xylylene 1 suggests that 1 is close to planar. The regular vibrational progression of ca. 1500 cm-1 seen in the absorption spectrum of 5b indicates a general increase in the lengths of the C= C bonds in the excited state. While 5b shows no tendency to thermally reclose upon standing at room temperature, irradiation at 350 nm either in rigid media or in fluid solution leads to a rapid nonstereospecific reclosure to regenerate the benzocyclobutenederivatives 2b and 3b.