Crossley Daniel L, Cid Jessica, Curless Liam D, Turner Michael L, Ingleson Michael J
School of Chemistry, University of Manchester , Manchester M13 9PL, United Kingdom.
Organometallics. 2015 Dec 28;34(24):5767-5774. doi: 10.1021/acs.organomet.5b00857. Epub 2015 Dec 8.
The addition of AlCl to four-coordinate boranes of the general formula (C-N-chelate)BCl results in halide abstraction and formation of three-coordinate borenium cations of the general formula [(C-N-chelate)BCl]. The latter react with both arylstannanes and arylsilanes by boro-destannylation and -desilylation, respectively, to form arylated boranes. Catalytic quantities of AlCl were sufficient to effect high-yielding arylation of (C-N-chelate)BCl. Boro-destannylation is more rapid than boro-desilylation and leads to double arylation at the boron center, whereas in reactions with arylsilanes either single or double arylation occurs dependent on the nucleophilicity of the arylsilane and on the electrophilicity of the borenium cation. The electrophilicity of the borenium cation derived from 2-phenylpyridine was greater than that of the benzothiadiazole analogues, enabling the boro-desilyation of less nucleophilic silanes and the direct electrophilic borylation of 2-methylthiophene.
向通式为(C-N-螯合物)BCl的四配位硼烷中加入AlCl会导致卤化物夺取，并形成通式为[(C-N-螯合物)BCl]的三配位硼正离子。后者分别通过硼脱锡反应和硼脱硅反应与芳基锡烷和芳基硅烷反应，形成芳基化硼烷。催化量的AlCl足以实现(C-N-螯合物)BCl的高产率芳基化。硼脱锡反应比硼脱硅反应更快，并导致硼中心的双芳基化，而在与芳基硅烷的反应中，单芳基化或双芳基化的发生取决于芳基硅烷的亲核性和硼正离子的亲电性。源自2-苯基吡啶的硼正离子的亲电性大于苯并噻二唑类似物的亲电性，这使得亲核性较低的硅烷能够进行硼脱硅反应以及2-甲基噻吩能够进行直接亲电硼化反应。
