Kinetics and mechanism of desulfurization reaction of 1-methyl-2-(substituted phenyl)-quinazoline-4(1H)-thiones in sodium methoxide solutions have been studied, giving the corresponding 1-methyl-2-(substituted phenyl)quinazolin-4(1H)-ones. The reaction proceeds in two steps. The first step involves splitting off of sulfur in the form of SH- and is much faster than the second step, whose rate is almost independent of the concentration of water in methanol. At lowest concentrations of methoxide, the rate of the first step increases linearly, but at higher concentrations a gradual decrease in the rate takes place. The rate of the second step, i.e. the transformation of the intermediate formed In into 1-methyl-2-(substituted phenyl)quinazolin-4(1H)-one (2a-2e), is independent of the methoxide concentration but increases with increasing concentration of water in methanol. On the basis of the kinetic dependences, the mechanism for both steps of desulfurization and the structure of intermediate In were proposed.
研究了1-甲基-2-(取代苯基)-喹唑啉-4(1H)-硫醇在甲醇钠甲醇溶液中脱硫反应的动力学和机理,得到相应的1-甲基-2-(取代苯基)喹唑啉-4(1H)-酮。该反应分为两步进行。第一步涉及以SH-形式脱离硫,比第二步快得多,其速率几乎不受甲醇中水的浓度影响。在甲醇最低甲醇浓度下,第一步的速率线性增加,但在较高浓度下,速率逐渐降低。第二步的速率,即将中间体In转化为1-甲基-2-(取代苯基)喹唑啉-4(1H)-酮(2a-2e),与甲醇中甲醇浓度无关,但随着水浓度的增加而增加。根据动力学依赖关系,提出了脱硫的两个步骤的机理和中间体In的结构。