Triplet Diphenylcarbenes Protected by Trifluoromethyl and Bromine Groups. A Triplet Carbene Surviving a Day in Solution at Room Temperature
作者:Tetsuji Itoh、Yoshimaru Nakata、Katsuyuki Hirai、Hideo Tomioka
DOI:10.1021/ja056575j
日期:2006.1.1
Two types of diphenyldiazomethanes having two trifluoromethyl and two bromine groups at the ortho positions, either in unsymmetrical or in symmetrical fashion, that is, (2,6-dibromo-4-phenylphenyl)[4-phenyl-2,6-bis(trifluoromethyl)phenyl]diazomethane (U-1-N2) and bis(2-bromo-4-phenyl-6-trifluoromethylphenyl)diazomethane (S-1-N2), are prepared. Triplet diphenylcarbenes (U-(3)1 or S-(3)1) are generated
在邻位具有两个三氟甲基和两个溴基团的两种类型的二苯基重氮甲烷,以不对称或对称方式,即 (2,6-二溴-4-苯基苯基)[4-苯基-2,6-双(三氟甲基) )苯基]重氮甲烷(U-1-N2)和双(2-溴-4-苯基-6-三氟甲基苯基)重氮甲烷(S-1-N2)。三重联苯卡宾(U-(3)1 或 S-(3)1)由这些前体生成,并通过低温下的 ESR、UV/vis 光谱以及室温下的时间分辨 UV/vis 光谱进行表征。这些卡宾的反应性比迄今为止已知的最稳定的三线态二苯基卡宾,即双(2,6-二溴-4-苯基苯基)卡宾低至少两个数量级。还表明,即使 S-(3)1 具有相同的两种取代基,S-(3)1 也比 U-(3)1 稳定得多。怀疑两个最庞大的基团的垂直排列是比平面组更有效地屏蔽碳烯中心的方法。通过这种方式,首次实现了在室温下在溶液中存活近一天的三重取代二苯卡宾。