Reactivities of Stable Rotamers. XXXIX. Thermal Decomposition of<b><i>t</i></b>-Butyl 3-Methyl-3-(substituted 9-triptycyl)peroxybutanoate Rotamers
作者:Michinori Oki、Ichiro Fujino、Daisuke Kawaguchi、Kazumasa Chuda、Yoko Moritaka、Yasunori Yamamoto、Shingo Tsuda、Tadashi Akinaga、Michihiko Aki、Hiroharu Kojima、Nobuhiro Morita、Makoto Sakurai、Shinji Toyota、Yasuhiro Tanaka、Toshihiro Tanuma、Gaku Yamamto
DOI:10.1246/bcsj.70.457
日期:1997.2
The ap and sc rotamers of the title compound, where substituents are 1,4-dimethyl, 1,4-dimethoxy, 1,2,3,4-tetrafluoro, and 1,2,3,4-tetrachloro, were thermolyzed in toluene solutions to examine the effects of interactions between the radical center and the substituent. The rates of thermolyses were affected neither by the substituent nor by the rotameric positions, but the product distributions showed dependence on the substituent. In the ap-forms, the effectively bulkier the substituent at the 1-position, the higher the yields of the 5-membered ring compound. This was attributed to the degree of the tilting of the 9-substituent, which forces the radical center to be pushed into the triptycene skeleton. For the sc-forms, the chloro and the methyl substituents exhibited special effects, the former affording a colligation product between benzyl and 2-(1,2,3,4-tetrachloro-9-triptycyl)-2-methylpropyl radicals and the latter showing a tendency of radical migration to the benzylic position. Comparison of the results of thermolyses of the 1,4-dimethyl peroxyester with those of 2(1H)-thioxo-1-pyridyl 3-(1,4-dimethyl-9-triptycyl)-3-methylbutanoate indicates that, although it is believed that these precursors afford the same 2-(1,4-dimethyl-9-triptycyl)-2-methylpropyl radicals, the product distributions were significantly different from each other. These results were attributed to the stabilizing effects of the sulfur compound on the radical in the solvent cage in the latter.
在甲苯溶液中对取代基为 1,4-二甲基、1,4-二甲氧基、1,2,3,4-四氟和 1,2,3,4-四氯的标题化合物的 ap 和 sc 转聚体进行热解,以考察自由基中心与取代基之间相互作用的影响。热解速率既不受取代基的影响,也不受转子位置的影响,但产物分布却与取代基有关。在 ap 型化合物中,1 位上的取代基越大,5 元环化合物的产量就越高。这是因为 9-取代基的倾斜程度迫使自由基中心挤入三庚烯骨架。对于 sc 形式,氯和甲基取代基显示出特殊效果,前者在苄基和 2-(1,2,3,4-四氯-9-三辛基)-2-甲基丙基自由基之间产生碰撞产物,后者则显示出自由基向苄基位置迁移的趋势。将 1,4-二甲基过氧化酯的热解结果与 2(1H)-硫酮-1-吡啶基 3-(1,4-二甲基-9-三甲苯基)-3-甲基丁酸酯的热解结果进行比较后发现,虽然认为这些前体产生的 2-(1,4-二甲基-9-三甲苯基)-2-甲基丙基自由基相同,但产物分布却明显不同。这些结果归因于硫化合物对后者溶剂笼中自由基的稳定作用。