Diverse disubstituted and trisubstituted thioureas were synthesized by the condensation of dithiocarbamate TEA (or DABCO) salts and amines using cerium ammonium nitrate (CAN) as a catalyst in high yields at room temperature. It is a one-pot method and it is unnecessary to isolate isothiocyanates. This reaction probably took place through nucleophilic addition of amines to isothiocyanates, which were generated by oxidative coupling of dithiocarbamates and the following decomposition of bis(aminothiocarbonyl)disulfides. When secondary amines and CS2 served as the reactants, bis(aminothiocarbonyl)disulfides were obtained via tandem nucleophilic addition/oxidative coupling reactions in moderate to excellent yields. In all the coupling reactions, the oxidant was air and CAN possibly acted as an SET catalyst.
多种二取代和三取代
硫脲通过二
硫代
氨基甲酸TEA(或
DABCO)盐与胺在室温下使用
硝酸铈铵(CAN)作为催化剂进行缩合反应,以高产率合成。这是一种一步法,无需分离异
硫氰酸酯。该反应可能涉及胺对异
硫氰酸酯的亲核加成,异
硫氰酸酯是由二
硫代
氨基甲酸盐的氧化偶联以及随后双(
氨基
硫羰基)二
硫化物的分解产生的。当使用二级胺和CS2作为反应物时,通过串联的亲核加成/氧化偶联反应,以中等至优异的产率获得了双(
氨基
硫羰基)二
硫化物。在所有偶联反应中,氧化剂为空气,CAN可能作为单电子转移催化剂发挥作用。