Green Synthesis Of Carbohydrazide And Its Related Heterocyclic Derivatives

Green chemistry is the chemistry that makes use of chemical technologies and methodologies to reduce or eliminate the use and generation of hazardous substances such as hazardous feedstocks, catalysts, solvents, reagents, products and by-products, and tries to prevent the pollution from beginning. Its goal is no longer to use nocuous substances, no longer to produce and dispose wastes. Green raw materials are a very important content for green chemistry. Dimethyl carbonate is a new kind of eco-friendly chemical material. It is called as "new foundation stone of organic chemistry".Carbohydrazide is widely used as a chemical deoxidant, metal corrosion inhibitor, boiler cleaning medium, resin finishing agent, antioxidant and solid reducing agent. Carbohydrazide is also used as component of propellant and crosslink agent of elastic fibre. Its derivatives have extensive applications in the area of analytic chemistry, material science and so on. Furthermore, carbohydrazide and its derivatives are important intermediates in organic synthesis. In addition, acylthiosemicarbazides, 1,3,4-thiadiazoles, 1,2,4-triazoles, 1,3,4-oxadiazoles and l,2,4-triazolo[3,4-6]-l,3,4-oxadiazoles have extensive biological activities. Therefore they have also been applied to many fields, for instance, medicine, agronomy, biology, etc.In this thesis, carbohydrazide and its derivatives, 1,5-diacyl carbohydrazides were first eco-friendly synthesized using nontoxic "green" reagent, dimethyl carbonate, as starting material. Then, a series of new compounds and their heterocyclic derivatives were further synthesized using carbohydrazide and 1,5-diacyl carbohydrazides as intermediates. In all of these new compounds, active moieties such as acylthiosemicarbazide, 1,3,4-thiadiazole, 1,2,4-triazole, and 1,3,4-oxadiazole are included respectively. The structures of all compounds were confirmed by IR, ~1H NMR, MS and elemental analysis. The experimental methodologies, results and possible mechanism were also proposed in this thesis.This thesis includes five chapters:Chapter 1: The development of carbohydrazide in synthesis, properties and applications.A brief introduction of green chemistry and "green" reagent, dimethyl carbonate, was first given. And then, we introduced the properties of carbohydrazide, expounded and compared its traditional and "green" preparation methods, and summarized its applications in chemical synthesis and industry.Chapter 2: Synthesis of sym-l,5-diacyl carbohydrazides.Carbohydrazide was first synthesized by reaction of nontoxic "green" reagent, dimethyl carbonate, with hydrazine hydrate. Then carbohydrazide readily reacted with a variety of acyl chlorides via several different methods to afford sixteen 1,5-diacyl carbohydrazides in high yield. This eco-friendly strategy efficiently avoids the use of extremely toxic phosgene, and has features of mild condition, short reaction period, and simple work-up procedure. Furthermore, synthetic methods were also discussed, and the structures of all compounds were confirmed by IR, ~1H NMR, MS and elemental analyses.Chapter 3: Synthesis of carbonyl bis(4-aroylthiosemicarbazide)s .Fifteen new carbonyl bis(4-aroylthiosemicarbazide)s were synthesized under phase transfer catalysis condition in high yield by two-step reactions: a variety of acyl chlorides first reacted with ammonium thiocyanate, then with carbohydrazide. The structures of all compounds were confirmed by IR, ~1H NMR, MS and elemental analyses.Chapter 4: Synthesis of l-(5'-arylcarboxamido-l',3',4'-thiazol-2'-yl)-4-aroyI-thiosemicarbazides.On the foundation of chapter 3, carbonyl bis(4-aryolthiosemicarbazide)s were cyclized to afford eleven new l-(5'-arylcarboxamido-l',3',4'-thiazol-2'-yl)-4-aroylthiosemicarbazides in the presence of glacial acetic acid. The structures of all compounds were confirmed by IR, 'H NMR, MS and elemental analyses.Chapter 5: Synthesis of 3,6-disubstituted-l,2,4-triazolo[3,4-b]-l,3,4-oxadiazoles.On the foundation of chapter 2, 1,5-diacyl carbohydrazides were dehydrated and cyclized further to afford fourteen n...