Boron tribromide as a reagent for anti-Markovnikov addition of HBr to cyclopropanes
作者:Matthew H. Gieuw、Shuming Chen、Zhihai Ke、K. N. Houk、Ying-Yeung Yeung
DOI:10.1039/d0sc02567d
日期:——
Although radical formation from a trialkylborane is well documented, the analogous reaction mode is unknown for trihaloboranes. We have discovered the generation of bromine radicals from boron tribromide and simple proton sources, such as water or tert-butanol, under open-flask conditions. Cyclopropanes bearing a variety of substituents were hydro- and deuterio-brominated to furnish anti-Markovnikov
尽管由三烷基硼烷形成自由基的记载已得到充分证明,但对于三卤硼烷而言,类似的反应模式尚不清楚。我们发现在开放烧瓶条件下,三溴化硼和简单的质子源(例如水或叔丁醇)会生成溴自由基。带有多种取代基的环丙烷被氢溴和氘代溴化,以高度区域选择性的方式提供了反马尔可夫尼科夫产品。NMR机理研究和DFT计算指向自由基途径,而不是BBr 3预期的常规离子机理。