THE EFFECT OF META-CYANO OR PARA-CYANO SUBSTITUTION ON THE REACTIVITY OF THE RADICAL CATIONS OF ARYLALKENES AND ALKANES - RADICAL IONS IN PHOTOCHEMISTRY .34.
THE EFFECT OF META-CYANO OR PARA-CYANO SUBSTITUTION ON THE REACTIVITY OF THE RADICAL CATIONS OF ARYLALKENES AND ALKANES - RADICAL IONS IN PHOTOCHEMISTRY .34.
复制标题
DOI：
10.1139/v95-042
复制
发表时间：
1995-03-01
期刊：
影响因子：
--
通讯作者：
CHEN, J
中科院分区：
文献类型：
--
作者：
ARNOLD, DR;DU, XY;CHEN, J
本文研究了吸电子取代基Meta氰基或对氰基对芳基烯烃和烷烃阳离子自由基反应活性的影响。自由基阳离子通过单电子转移（SET）到电子接受光敏剂产生。研究了三种反应：（i）将亲核试剂加成到芳基烯烃的自由基阳离子上，（ii）裂解芳基烷烃的自由基阳离子的苄基碳-碳键;和（iii）芳基烷烃的自由基阳离子的苄基碳-氢键的去质子化。自由基阳离子4-（1-苯基乙烯基）苯甲腈（1b），3-（1-苯基乙烯基）苯甲腈（1c），4（2-甲氧基-1-苯基乙基）苄腈（2b），3-（2-甲氧基-1-苯基乙基）苯甲腈（2c）、顺式-和反式-5-氰基-2-甲氧基-1-苯基茚满在乙腈-甲醇溶液中，通过单电子转移到1，4-二氰基苯（3）的最低激发单重态，生成6-氰基-3-苯基茚（7 b）和6-氰基-3-苯基茚（6 b-cis and -trans）。1b、1c和7 b的自由基阳离子与甲醇反应生成反马尔科夫尼科夫加合物（2b、2c和6 b-顺式和6 b-反式）。2b、2c和6 b-反式的自由基阳离子在苄基碳-碳键处裂解，得到由自由基和碳阳离子片段衍生的产物。自由基阳离子的6 b-顺式去质子化从苄基的位置，随后形成的非对映体，6 b-trans. This行为可以解释/预测的基础上提出的这些反应的机制。分子轨道计算（AM 1）支持的结论。
The effect of electron-withdrawing substituents, meta- or para-cyano, on the reactivity of the radical cation of arylalkenes and alkanes has been determined. The radical cations were generated by single electron transfer (set) to an electron-accepting photosensitizer. Three reactions were studied: (i) the addition of nucleophile to the radical cation of arylalkenes, (ii) cleavage of the benzylic carbon-carbon bond of the radical cation of arylalkanes; and (iii) the deprotonation of the benzylic carbon-hydrogen bond of the radical cation of arylalkanes. The radical cations of 4-(1-phenylethenyl)benzonitrile (1b), 3-(1-phenylethenyl)benzonitrile (1c), 4(2-methoxy- 1-phenylethyl)benzonitrile (2b), 3-(2-methoxy- l-phenylethyl)benzonitrile (2c), cis- and trans-5-cyano-2-methoxy- 1-phenylindane (6b-cis and -trans), and 6-cyano-3-phenylindene (7b) were generated, by single electron transfer to the lowest excited singlet state of 1,4-dicyanobenzene (3), in acetonitrile-methanol. The radical cations of 1b, 1c, and 7b react with methanol to yield the anti-Markovnikov adducts (2b, 2c, and 6b-cis and 6b-trans). The radical cations of 2b, 2c, and 6b-trans cleave at the benzylic carbon-carbon bond to give products derived from the radical and carbocation fragments. The radical cation of 6b-cis deprotonates from the benzylic position with subsequent formation of the diastereomer, 6b-trans. This behaviour can be explained/predicted on the basis of the proposed mechanisms for these reactions. Molecular orbital calculations (AM1) support the conclusions.