Generation and Reactivities of Triplet Diphenylcarbenes Protected by Bulky Groups as para Substituents
Generation and Reactivities of Triplet Diphenylcarbenes Protected by Bulky Groups as para Substituents
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大基团作为对位取代基保护的三重态二苯基碳烯的生成和反应性
DOI：
10.1002/poc.1898
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
and Hideo Tomioka
中科院分区：
文献类型：
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作者：
Katsuyuki Hirai;Keiji Hatanaka;Tsuyoshi Yamaguchi;Akiko Miyajima;Toshikazu Kitagawa;and Hideo Tomioka
合成了4，4 ′-位含10-（4-叔丁基-2，6-二甲基苯基）-2，7-二（苯乙炔基）-9-蒽基乙炔基的双（2，6-二甲基苯基）重氮甲烷（1b-N2）。通过前体的光解生成了三重态二苯基卡宾31 b，并通过低温下的电子自旋共振和紫外-可见光谱以及室温下的激光闪光光解技术对其进行了表征。在77 K下照射2-甲基四氢呋喃基质中的1b-N2，得到归因于三重态卡宾31 b的电子自旋共振信号。通过在相同条件下照射1b-N2获得31 b的UV-Vis光谱。1b-N2在脱气苯溶液中的激光闪光光解产生了归因于31 b的瞬态吸收带，其以一级方式衰减，速率常数为0.46 s-1。该卡宾的反应性低于在4，4 ′-位具有9-蒽基乙炔基的三重态双（2，6-二甲基苯基）卡宾（31 a），其以二级方式衰变，速率常数（2k/εl）为0.69 s-1。三重态卡宾31 b被氧捕获生成酮氧化物1b-O，速率常数为1.9 × 107 M-1 s-1，也被1，4-环己二烯捕获，速率常数为1.2 M-1 s-1。类似的研究表明，在4，4 ′-位上分别具有大体积取代基的10-（4-叔丁基-2，6-二甲基苯基）-2，7-双[3，5-二（苯乙炔基）苯乙炔基]-9-蒽基乙炔基和10-（4-叔丁基-2，6-二甲基苯基）-2，7-双（9-三丁基乙炔基）-9-蒽基乙炔基的二苯基重氮甲烷（1c-N2和1d-N2）的相应三重态卡宾31 c和31 d比31 b更持久。在脱气的苯中稳态辐照1a-N2、1c-N2和1d-N2，分别以83%、50%和51%的产率得到四芳基乙烯2a、2c和2d。版权所有© 2011约翰威利父子有限公司.
Bis(2,6‐dimethylphenyl)diazomethane (1b‐N2) having 10‐(4‐tert‐butyl‐2,6‐dimethylphenyl)‐2,7‐di(phenylethynyl)‐9‐anthrylethynyl groups at the 4,4′‐positions was synthesized. Triplet diphenylcarbene31b was generated by photolysis of the precursor and was characterized by electron spin resonance and UV–Vis spectroscopies at low temperature, and laser flash photolysis techniques at room temperature. Irradiation of 1b‐N2in a 2‐methyltetrahydrofuran matrix at 77 K gave electron spin resonance signals ascribable to triplet carbene31b. UV–Vis spectra of31b were obtained by irradiating 1b‐N2under identical conditions. The laser flash photolysis of 1b‐N2in a degassed benzene solution gave transient absorption bands ascribable to31b, which decayed in a first‐order fashion with a rate constant of 0.46 s–1. The carbene was shown to be less reactive than the triplet bis(2,6‐dimethylphenyl)carbene (31a) having 9‐anthrylethynyl groups at the 4,4′‐positions, which decayed in a second‐order fashion with a rate constant (2k/εl) of 0.69 s–1. Triplet carbene31b was trapped by oxygen to generate ketone oxide 1b‐O with a rate constant of 1.9 × 107M–1s–1and also by 1,4‐cyclohexadiene with a rate constant of 1.2 M–1s–1. Similar studies with diphenyldiazomethanes (1c‐N2and 1 d‐N2) having bulky substituents, 10‐(4‐tert‐butyl‐2,6‐dimethylphenyl)‐2,7‐bis[3,5‐di(phenylethynyl)phenylethynyl]‐9‐anthrylethynyl and 10‐(4‐tert‐butyl‐2,6‐dimethylphenyl)‐2,7‐bis(9‐triptycylethynyl)‐9‐anthrylethynyl groups at the 4,4′‐positions respectively indicated that the corresponding triplet carbenes31c and31 d were more persistent than31b. Steady‐state irradiation of 1a‐N2, 1c‐N2, and 1 d‐N2in degassed benzene afforded tetraarylethenes 2a, 2c, and 2d in 83, 50, and 51% yield, respectively. Copyright © 2011 John Wiley & Sons, Ltd.