H₂SO₄-SiO₂Catalyzed Synthesis Oftetrazoles And Its Antifungal Activities

Tetrazoles are five heterocyclic compounds containing four nitrogen atoms. They arewidely found in nature such as purine, pyrimidine, and many other natural products, alsomany synthetic drugs contain tetrazole groups. Its metal salts (or complexes) can be used inimportant class of energetic materials as high-energy propellant and explosives.The most direct synthesis of tetrazoles is the addition of the azide to nitriles via [2+3]cycloaddition. According to the literature research, the conventional method of synthesizingtetrazoles has many drawbacks. Therefore we are looking for another method for the synthesisof tetrazoles. It has a H₂SO₄-SiO₂as the solid acid catalyst for the first time, lower thetemperature, and the optimized processing conditions. Finally we get a series of tetrazolecompounds in good yield. The main results were as follows:1. Three different proportions of H₂SO₄-SiO₂solid acids were prepared by sol-gelmethods. We optimize the experimental conditions with benzonitrile and sodiumazide as thesubstrates. The optimal reaction conditions results show that the ratio of H₂SO₄-SiO₂is0.5:1,the solvent is DMF. Catalyst can be reused for three cycles with consistent activity.2. Work up with alkaline solution to form the tetrazole salts, other impurities wereremoved by washing with organic solvent. And then acidification the alkaline solution withhydrochloric acid, followed by extracted with ethyl acetate. At last the organic phase wasdried and tetrazoles were got by recrystallization. Finally we generated12different groupsderivatives, yield of70%～90%, all of these confirmed by NMR, MS, IR.3. Apply mycelium growth rate method,12compounds were determined by antifungalactivity of five plant pathogenic fungi. We choose the Botrytis cinerea,Alternaria solani,Fusarium solani, Pyricularia grisea, Colletotrichum gloeosporioide as testedphytopathogenic fungi, choose the acetone as control. Compounds2d,2i have satisfactoryinhibitory in all of five tested fungi, the inhibition rates reached20%～50%, However theantibacterial effects of other compounds is not obvious.