Kinetics and mechanism of methanolysis and cyclization of 1-acyl-3-(2-halo-5-nitrophenyl)thioureas
作者:Miloš Sedlák、Jiří Hanusek、Michal Holčapek、Vojeslav Štěrba
DOI:10.1002/poc.351
日期:2001.3
The kinetics of methoxide ion-catalysed solvolysis of 1-acyl-3-(2-halo-5-nitrophenyl)thioureas and cyclization of fluoro derivatives were studied in methanol at 25 °C. The cyclization involved the substitution of fluorine by sulphur anion of thiourea and proceeded in two steps. With the acetyl derivative, the first step is methanolysis and the second step is much slower cyclization of the 2-fluoro
在25°C的甲醇中研究了甲氧基离子催化1-酰基-3-(2-卤代5-硝基苯基)硫脲的溶剂分解动力学和氟衍生物的环化反应。环化涉及用硫脲的硫阴离子取代氟,并分两步进行。对于乙酰基衍生物,第一步是甲醇分解,第二步是形成2-氟-5-硝基-1,3-苯并噻唑的2-氟-5-硝基苯基硫脲阴离子的环化慢得多。对于苯甲酰基衍生物,第一步涉及苯甲酰基的平行甲醇解和环化成2-苯甲酰基氨基-5-硝基-1,3-苯并噻唑。当甲醇钠的浓度高于约0.01 mol l -1时,所有酰基卤代硫脲的溶剂分解速率都会降低,而当浓度高于约0.4 mol l时-1除环化产物外,其他产物的形成也有所增加。加入18-crown-6后,未形成副产物,并且大大加速了氟衍生物的环化。溶剂分解反应的减慢和环化反应的加速最有可能是由于二价阴离子的形成。版权所有©2001 John Wiley&Sons,Ltd.