Ring closure of 2,2-dimethyloct-7-en-3-yl radical: a system exhibiting unusual solvent dependence
作者:L.J. Athelstan、Matthew D. Cliff、Carl H. Schiesser
DOI:10.1016/s0040-4020(01)81238-2
日期:1992.1
The ring closure of the 2,2-dimethyloct-7-en-3-yl radical (1) has been studied. In hexane at 25°C, reaction of the radical precursor, O-(2,2-dimethyloct-7-en-3-yl)-O-phenylthionocarbonate (8) with tri-n-butyltin hydride (AIBN initiator) proceeds to give -1-tert-butyl-2-methylcyclopentane (10) as the major ring closed product (/ = 3.1). The rate constant for the -mode of ring closure was found to be
已经研究了2,2-二甲基辛-7-烯-3-基的闭环(1)。在25°C的己烷中,自由基前体O-(2,2-二甲基辛-7-烯-3-基)-O-苯硫代碳酸氢盐(8)与氢化三正丁基锡(AIBN引发剂)的反应进行至给-1-叔丁基-2-甲基环戊烷(10)作为主要环封闭产物(/ = 3.1)。发现在25°C时,闭环-模式的速率常数为8.7×10 4 s -1,活化能为5.5 kcal.mol -1,而环化-模式的相应值为2.8× 10 4 s -1和8.7 kcal.mol-1。立体选择性显示通常的温度依赖性。令人惊讶地,当溶剂极性(增加的立体选择性也提高/ 1-丙醇= 5.9在25℃),这种现象以前没有鉴定。