Kiesewetter Matthew K, Gard Matthew N, Reiter Richard C, Stevenson Cheryl D
Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, USA.
J Am Chem Soc. 2006 Dec 13;128(49):15618-24. doi: 10.1021/ja062846u.
The low temperature complete dehydrohalogenation of pentabromocyclododecene (C12H17Br5) with potassium tert-butoxide in THF followed by exposure to potassium metal leads to the formation of the anion radical of 1,5-di-trans-[12]annulene, which loses hydrogen and undergoes ring closure to form the anion radical of 11,12-dihydro-[8]annuleno-[6]annulene. This product can, in turn, be isolated as its neutral molecule via reoxidation with iodine. A [12]annulene obtained via the dimerization of 1,5-hexadiyne in the presence of 18-crown-6 and potassium tert-butoxide undergoes ring closure, with concomitant loss of hydrogen, to yield the heptalene anion radical. It follows that the heptalene anion radical precursor was the 1,7-di-trans isomer of [12]annulene.
在四氢呋喃中，用叔丁醇钾使五溴环十二烯（C₁₂H₁₇Br₅）进行低温完全脱卤化氢反应，随后与金属钾接触，会生成1,5 - 二反式 - [12]轮烯的阴离子自由基，该自由基失去氢并发生闭环反应，形成11,12 - 二氢 - [8]轮烯并[6]轮烯的阴离子自由基。通过用碘再氧化，该产物又可以作为其中性分子被分离出来。在18 - 冠 - 6和叔丁醇钾存在下，通过1,5 - 己二炔二聚反应得到的[12]轮烯发生闭环反应，同时失去氢，生成庚搭烯阴离子自由基。由此可知，庚搭烯阴离子自由基的前体是[12]轮烯的1,7 - 二反式异构体。
