3-[4′-(Diethylboryl)phenyl]pyridine: Exclusive Crystallization of the Cyclic Tetramer
作者:Shigeharu Wakabayashi、Natsu Sugiyama、Yasuhiro Ohki、Takahito Itoh、Toshikazu Kitagawa
DOI:10.1002/asia.201801698
日期:2019.2.15
spectroscopy of precipitates of compound 1 suggested that precipitation from acetone and toluene each afforded mixtures of the cyclic trimer and the cyclic tetramer, whereas precipitation from benzene exclusively furnished the cyclic tetramer. Therefore, it appeared that crystallization readily shifted the equilibrium towards the cyclic tetramer in benzene. The thermodynamic parameters for the equilibrium between
3– [4'-(二乙基硼基)苯基]吡啶(1)在丙酮中于0°C时在溶液中以环状三聚体为主要成分的低聚物混合物形成结晶,得到共结晶的环状四聚体与溶剂分子。类似地,化合物1在10°C的甲苯中和在8°C的苯中的溶液分别为环状四聚体提供了甲苯和苯分子的结合,因此表明环状四聚体是次要成分。化合物1沉淀物的13 C CP / MAS NMR光谱提示从丙酮和甲苯中沉淀可分别得到环状三聚体和环状四聚体的混合物,而从苯中沉淀仅可提供环状四聚体。因此,似乎结晶容易使平衡向苯中的环状四聚体移动。根据van't Hoff图确定,[D 6 ]苯中这两种低聚物之间平衡的热力学参数为ΔH °= -8.8 kcal mol -1和ΔS °= -23.7 cal mol -1 K -1,与先前报道的计算和观察结果一致。