Polarity Reversal Catalysis in Radical Reductions of Halides by N-Heterocyclic Carbene Boranes
作者:Xiangcheng Pan、Emmanuel Lacôte、Jacques Lalevée、Dennis P. Curran
DOI:10.1021/ja300416f
日期:2012.3.28
ineffective radical reductions of alkyl and aryl halides by N-heterocyclic carbene boranes (NHC-boranes) are catalyzed by thiols. Reductions and reductive cyclizations with readily available 1,3-dimethylimidazol-2-ylidene borane and a water-soluble triazole relative are catalyzed by thiophenol and tert-dodecanethiol [C(9)H(19)C(CH(3))(2)SH]. Rate constants for reaction of the phenylthiyl (PhS•) radical with
否则,N-杂环卡宾硼烷(NHC-硼烷)对烷基和芳基卤化物的缓慢或完全无效的自由基还原由硫醇催化。使用容易获得的 1,3-二甲基咪唑-2-亚基硼烷和水溶性三唑相关物的还原和还原环化反应由苯硫酚和叔十二烷硫醇催化 [C(9)H(19)C(CH(3))(2 )SH]。苯硫基 (PhS•) 自由基与两个 NHC 硼烷反应的速率常数已通过激光闪光光解实验测量为 ~10(8) M(-1) s(-1)。对现有证据的分析表明极性反转催化的作用。