平面 N-杂环卡宾二芳基硼翁离子的合成：通过阳离子硼化反应和与路易斯碱的反应。
Planar N-heterocyclic carbene diarylborenium ions: synthesis by cationic borylation and reactivity with Lewis bases.
机构信息
Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Ontario, M5S 3H6 (Canada).
出版信息
Angew Chem Int Ed Engl. 2015 Apr 20;54(17):5214-7. doi: 10.1002/anie.201500198. Epub 2015 Mar 10.
The NHC-borane adduct (IBn)BH3 (1) (NHC= N-heterocyclic carbene; IBn=1,3-dibenzylimidazol-2ylidene) reacts with [Ph3 C][B(C6 F5 )4 ] through sequential hydride abstraction and dehydrogenative cationic borylation(s) to give singly or doubly ring closed NHC-borenium salts 2 and 3. The planar doubly ring closed product [C3 H2 (NCH2 C6 H4 )2 B][B(C6 F5 )4 ] is resistant to quaternization at boron by Et2 O coordination, but forms classical Lewis acid-base adducts with the stronger donors Ph3 P, Et3 PO, or 1,4-diazabicyclo[2.2.2]octane (DABCO). Treatment of 3 with tBu3 P selectively yields the unusual oligomeric borenium salt trans-[(C3 H2 (NCH2 C6 H4 )2 B)2 (C3 H2 (NCHC6 H4 )2 B)][B(C6 F5 )4 ] (7).
NHC-硼烷加合物 (IBn)BH3（1）（NHC= 杂环卡宾；IBn=1,3-二苄基咪唑-2-亚基）通过顺序氢化物抽提和脱氢阳离子硼化反应与 [Ph3 C][B(C6 F5 )4 ] 反应，得到单环或双环闭合的 NHC-硼翁盐 2 和 3。平面双环闭合产物 [C3 H2 (NCH2 C6 H4 )2 B][B(C6 F5 )4 ] 不易被 Et2 O 配位季铵化，但可与更强的供体 Ph3 P、Et3 PO 或 1,4-二氮杂双环[2.2.2]辛烷 (DABCO) 形成经典的路易斯酸碱加合物。用 tBu3 P 处理 3 可选择性地得到不寻常的齐聚硼翁盐反式-[(C3 H2 (NCH2 C6 H4 )2 B)2 (C3 H2 (NCHC6 H4 )2 B)][B(C6 F5 )4 ]（7）。
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