Study On The Green Synthesis Process Of Dimethyl Carbodithiocyanamate

Dimethyl carbodithiocyanamate is an important organic synthesis intermediate which is mainly used as a synthetic intermediate for cimetidine,statin and other drugs.It is also widely used in the synthesis of pesticides and fungicides.At present,the production process of dimethyl carbodithiocyanamate is mainly using dimethyl sulfate as a methylation reagent.However,dimethyl sulfate is hypertoxic,and it can cause serious harm to the human body when it is touched or inhaled by the skin.At the same time,it also has a strong toxic pollution effect on the environment.Because of the corrosive effect on the equipment,the traditional synthesis process of dimethyl carbodithiocyanamate is increasingly incompatible with the requirements of social development.In recent years,dimethyl carbonate has been widely welcomed by scholars at home and abroad because of its excellent environmental protection and specific reactivity.Therefore,it plays an extremely important role in improving the synthesis process of dimethyl carbodithiocyanamate by using dimethyl carbonate instead of dimethyl sulfate as methylation reagent.In this paper,environmentally friendly reagent dimethyl carbonate was used as methylation reagent,and a new green synthesis process of dimethyl carbodithiocyanamate was introduced in detail.Meanwhile,in order to solve the problem of low yield of methylation reaction of dimethyl carbonate,two kinds of zirconium catalysts were prepared with zirconium as the core:One was solid super-acid zirconium dioxide(SO₄^2-/ZrO₂)and the other was zirconium-based metal organic framework material?UIO-66?.The catalytic effects of two catalysts on the synthesis of dimethyl carbodithiocyanamate were studied,and the factors affecting the methylation reaction of dimethyl carbonate were investigated.The results show that SO₄^2-/ZrO₂ has the best catalytic effect on the reaction,and the higher acid strength of the catalyst,the stronger catalytic ability of methylation reaction of dimethyl carbonate.In addition,the green synthesis process of dimethyl carbodithiocyanamate was optimized.Salt formation and methylation reactions were investigated by single factor method and the best process was:In the synthesis of N-cyanoimido-S,S-dithiocarbonate salt,deionized water as solvent,the mass ratio of solvent to calcium cyanamide was 4:1,and the molar ratio of calcium cyanamide,carbon disulfide to potassium hydroxide was 1:1:2.1.PEG-400 was used as phase transfer catalyst,the mass ratio of PEG-400 to calcium cyanamide was 0.12:1,the reaction temperature was kept at 40°C,the reaction time was kept at 5 h,the reaction was continuously stirred,and the final yield was 83.0%;In the synthesis of dimethyl carbodithiocyanamate,emulsion?water,ethylene glycol,OP-10 and turkey red oil in a mass ratio of 12:1:1:0.5?as solvent,the mass ratio of solvent to N-cyanoimido-S,S-dithiocarbonate is 3:1,the molar ratio of N-cyanoimido-S,S-dithiocarbonate salt to dimethyl carbonate was1:12,the SO₄^2-/ZrO₂ prepared at 600°C calcination conditions was used as catalyst,and PEG-400 was used as phase transfer catalyst,the mass ratio of N-cyanoimido-S,S-dithiocarbonate salt,SO₄^2-/ZrO₂ and PEG-400 was 1:0.04:0.06,the reaction temperature was maintained at 180°C,the reaction time was maintained at 8 h,continuous stirring and reflux reaction,and the final yield was 39.2%.In this optimal process,the overall yield of dimethyl carbodithiocyanamate was 32.5%which slightly higher than the actual yield of the process used in the current plant.