由4-联苯甲酰胺合成4-联苯腈

Preparation of Biphenyl-4-carbonitrile from Biphenyl-4-carboxamide

研究了在二氯乙烷中4-联苯甲酰胺合成4-联苯腈的脱水工艺,考察了氯化亚砜用量和二甲基甲酰胺(DMF)用量等因素对该反应的影响,由此获得了较佳的反应参数:DMF的用量为4-联苯甲酰胺摩尔数的1/2,氯化亚砜为4-联苯甲酰胺摩尔数的4倍,反应时间5h,反应温度为80°C,如此可以75.8%的收率得到4-联苯腈。在氨气氛围中,不使用任何脱水剂,4-联苯甲酰胺可在高温(240°C)时转化成4-联苯腈,通过减压蒸馏(2～3mmHg)可以70%收率得到产物。在此反应中,温度是关键的影响因素,当温度低于220°C时,反应进展缓慢;温度高于240°C时,对提高反应速度的意义不大。

Biphenyl-4-carbonitrile can be obtained from biphenyl-4-carboxamide by dehydrating reaction in dimethylformamide （DMF） by using thionyl chloride as dehydrating agent at low temperature （5℃）; But DMF is difficult to be recovered because it is soluble in water, so the above reaction is not so friendly to the environment. However biphenyl-4-carbonitrile could be obtained from biphenyl-4-carboxamide in dichloroethane by using thionyl chloride as dehydrating agent. The factors affecting the reaction was investaged, and the optimal reaction parameters were obtained as follows： the molar ratios of DMF to biphenyl-4-carboxamide and thionyl chloride to biphenyl-4-carboxamide are 1：2 and 4：1, respectively, the reaction time and temperature are 5 h and 80℃, respectively. Under above reaction conditions, the biphenyl-4-carbonitrile yield of 75.8% could be obtained. Meanwhile the biphenyl-4-carboxamid could also be converted to biphenyl-4-carbonitrile at high temperature in ammonia atmosphere without any dehydrating agent and after distillation under reduced pressure （2-3 mmHg）, the biphenyl-4-carbonitrile yield of 70% could obtained. For above process, the temperature is the key factor, when the temperature is lower than 220℃, the reaction rate is very low; however when the temperature is higher than 240℃, the acceleration effect of the temperature on the reaction rate is not so obviously.