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首页> 外文期刊>Chemistry: A European journal >Aryl Cation and Carbene Intermediates in the Photodehalogenation of Chlorophenols
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Aryl Cation and Carbene Intermediates in the Photodehalogenation of Chlorophenols

机译：氯酚光脱卤中的芳基阳离子和碳中间体

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摘要

The photochemistry of 2,6-dimethyl-4-chlorophenol(6)has been studied in methanol and trifluoroetha-nol(TFE)through product studies and transient absorption spectroscopy.Chloride loss from triplet 6 gave triplet hydroxyphenyl cation 14,which equilibrated with triplet oxocyclohexadieny-lydene 15 within a few tens of nanoseconds;the cation can,however,be selectively trapped by allyltrimethylsilane(k_(ad)= 10~8-10~9 M~(-1)s~(-1))to give a pheno- nium ion and the allylated phenol.In neat alcohols,14 and 15 are reduced through different mechanisms,namely by hydrogen transfer through radical cation 17 and via phenoxyl radical 16,respectively.The mechanistic rationalization has been substantiated by the parallel study of an O-silylated derivative.The work shows that the chemistry of the highly(but selectively)reactive phenyl cation 14 can not only be discriminated from that of the likewise highly reactive carbene 15,but also exploited for synthetically useful reactions,as in this case with alkenes.Photolysis of electron-donating substituted halobenzenes may be the method of choice for the mild generation of some classes of phenyl cations.
机译：通过产物研究和瞬态吸收光谱法研究了2,6-二甲基-4-氯苯酚（6）在甲醇和三氟乙基-醇（TFE）中的光化学作用。三重态6的氯离子流失产生了三重态羟基苯基阳离子14，与三重态平衡。氧代环己二烯基-lydene 15在几十纳秒内;但是阳离子可以被烯丙基三甲基硅烷（k_（ad）= 10〜8-10〜9 M〜（-1）s〜（-1））选择性捕获在纯醇中，14和15通过不同的机理被还原，即分别通过自由基阳离子17和苯氧自由基16进行氢转移。这项工作表明，高（但选择性）反应性苯基阳离子14的化学不仅可以与同样具有高反应性的卡宾15区别开来，而且还可以用于合成上有用的反应，在这种情况下与alk给电子取代的卤代苯的光解可能是温和生成某些类别的苯基阳离子的一种选择方法。

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