Synthesis Research Of O-nitrobenzaldehyde

o-Nitrobenzaldehyde is a very important organic intermediate and widely used in medicine, pesticide and fine chemicals, i.e., it can be used to prepare cardiovascular drugs such as nitro-pyridine and NESO. There are several methods such as Bromination and direct oxidation to synthesize o-nitrobenzaldehyde, and bromination-hydration-oxidation process is applied in industrial scale manufacture. Unfortunately, this process has some defects such as harsh reaction conditions, high toxicity, special requirement to production equipment and heavy pollution.A new and green method was developed to synthesize o-nitrobenzaldehyde in this dissertation including base-catalyzed condensation of o-nitrotoluene with ethyl oxalate and oxidation. In the firstly step, alkali alcoholate was used as the strong basic catalyst in the condensation reaction and unreacted o-nitrotoluene could be simply recovered. The next step involved oxidation by KMnO4 and H2O2. The optimized reaction conditions was achieved by factor and orthogonal experiments. o-Nitrobenzaldehyde was indentified by GC-MS, IR, H-NMR, etc.The optimized reaction conditions of the condensation were as follows:reaction catalyzed by the C2H5OK, n(o-nitrotoluene): n(diethyl oxalate):n(C2H5OK)=1:1.5:1.5, reaction temperature 80℃and reaction time 30 min. Under these conditions, the conversion of o-nitrotoluene comes up to 84.7%. Using KMnO4 as the oxidant, cyclohexane as the solvent, the optimum conditions of the oxidation were as follows:n(KMnO4): n(o-nitrotoluene)=2:3, reaction temperature 10℃, pH 10, and reaction time 30 min, o-nitrobenzaldehyde could be obtained in a yield of 40.7%, and if H2O2 was used as the oxidant and Na2WO4 as the catalyst, o-nitrobenzaldehyde could be obtained in a higher yield of 43.2% when reacting at pH 11 and 15℃.The new process avoids the bromination step involving high toxic bromine and tetrachloromethane, and H2O2 was used as the oxidant in the final step. Totally, this process has some exciting merits such as simple operation, low cost, no There are some advantage such as a bit simple process, no special requirement to production equipment, recyclable substrate and environmentally friendly, which makes it more prospective for practical applicatoin.