The B(C6F5)3 Boron Lewis Acid Route to Arene-Annulated Pentalenes
The B(C6F5)3 Boron Lewis Acid Route to Arene-Annulated Pentalenes
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DOI：
10.1002/asia.201400096
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发表时间：
2014-06-01
影响因子：
4.1
通讯作者：
Erker, Gerhard
中科院分区：
文献类型：
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作者：
Chen, Chao;Harhausen, Marcel;Erker, Gerhard
4，5-二甲基-1，2-双（1-萘乙炔基）苯（12）在用强硼刘易斯酸B（C6 F5）（3）处理时经历快速的多环闭合反应，得到多环平面共轭体系13（50%产率）。在该反应过程中，C6 F5基团从硼转移到碳。用CH 3B（C6 F5）（2）处理12类似地进行，得到13（C6 F5-转移）和产物15的混合物，产物15通过CH 3-基团转移形成。类似地，1，2-双（苯基乙炔基）苯（8a）与CH 3B（C6 F5）（2）反应，得到相应的C6 F5-和CH 3-取代的二苯并环戊二烯10a和16的混合物。该反应被认为通过表现出乙烯基阳离子反应性的两性离子中间体进行。一些B（C6 F5）（3）-取代的物质（26，27）因此通过在用受抑刘易斯对B（C6 F5）（3）/P（邻甲苯基）（3）处理相应的1，2-双（炔基）苯原料（24，8）时原位去质子化而形成。C6 F5取代产物的整体形成形式上需要在中间脱硼步骤中HB（C6 F5）（2）裂解。这在含噻吩基乙炔基的起始材料21与B（C6 F5）（3）的反应中得到证实，其得到相应的环化并环戊二烯产物23，其具有1，4-加成到其噻吩环上的HB（C6 F5）（2）部分。化合物12 -14、23和26通过X射线衍射表征。
4,5-Dimethyl-1,2-bis(1-naphthylethynyl)benzene (12) undergoes a rapid multiple ring-closure reaction upon treatment with the strong boron Lewis acid B(C6F5)(3) to yield the multiply annulated, planar conjugated -system 13 (50% yield). In the course of this reaction, a C6F5 group was transferred from boron to carbon. Treatment of 12 with CH3B(C6F5)(2) proceeded similarly, giving a mixture of 13 (C6F5-transfer) and the product 15, which was formed by CH3-group transfer. 1,2-Bis(phenylethynyl)benzene (8a) reacts similarly with CH3B(C6F5)(2) to yield a mixture of the respective C6F5- and CH3-substituted dibenzopentalenes 10a and 16. The reaction is thought to proceed through zwitterionic intermediates that exhibit vinyl cation reactivities. Some B(C6F5)(3)-substituted species (26, 27) consequently formed by in situ deprotonation upon treatment of the respective 1,2-bis(alkynyl)benzene starting materials (24, 8) with the frustrated Lewis pair B(C6F5)(3)/P(o-tolyl)(3). The overall formation of the C6F5-substituted products formally require HB(C6F5)(2) cleavage in an intermediate dehydroboration step. This was confirmed in the reaction of a thienylethynyl-containing starting material 21 with B(C6F5)(3), which gave the respective annulated pentalene product 23 that had the HB(C6F5)(2) moiety 1,4-added to its thiophene ring. Compounds12-14, 23, and 26 were characterized by X-ray diffraction.