The Thermal Rearrangement of an NHC‐Ligated 3‐Benzoborepin to an NHC‐Boranorcaradiene
The Thermal Rearrangement of an NHC‐Ligated 3‐Benzoborepin to an NHC‐Boranorcaradiene
复制标题
NHC 的热重排 - 连接 3 - 苯并硼平与 NHC - 硼烷二烯
DOI：
10.1002/ange.201912234
复制
发表时间：
2019
影响因子：
--
通讯作者：
Taniguchi, Tsuyoshi
中科院分区：
文献类型：
--
作者：
Shimoi, Masaki;Kevlishvili, Ilia;Watanabe, Takashi;Maeda, Katsuhiro;Geib, Steven J.;Curran, Dennis P.;Liu, Peng;Taniguchi, Tsuyoshi
通过苯并[3，4]环-3-烯-1，5-二炔与N-杂环卡宾硼烷的双自由基氢化反应，合成了桥联结构的N-杂环卡宾连接的3-苯并苯并[3，4]环-3-烯-1，5-二炔。NHC连接的钻柱在150 °C下的热反应生成了可分离的NHC-硼杂二烯。实验和密度泛函理论计算支持这样一种机制，即通过热6π电环反应，钻柱最初重排为硼碳二烯。然后是1，5-硼位移，得到重排的硼或卡拉二烯。这种转变是通过具有开壳双自由基性质的过渡态在硼上发生的立体反转而发生的。这是第一个从钻柱的热反应中分离出硼碳二烯的例子。
An N‐heterocyclic‐carbene‐ligated 3‐benzoborepin with a bridged structure has been synthesized by double radicaltrans‐hydroboration of benzo[3,4]cycloundec‐3‐ene‐1,5‐diyne with an N‐heterocyclic carbene borane. The thermal reaction of the NHC‐ligated borepin at 150 °C gives an isolable NHC‐boranorcaradiene. Experiments and density functional theory calculations support a mechanism whereby the borepin initially rearranges to a boranorcaradiene by a thermal 6π‐electrocyclic reaction. This is followed by 1,5‐boron shift to give a rearranged boranorcaradiene. This shift occurs with stereoinversion at boron through a transition state with open‐shell diradical character. This is the first example of the isolation of a boranorcaradiene from a thermal reaction of a borepin.