Novel Process For The Synthesis Of Pyridine N-oxides

Pyridine N-Oxides are important intermediates of fine chemicals,such as Omeprazole,Pyrithione Zinc,Acetamiprid,Forchlofenuron.Traditional CH₃COOH-H₂O₂ chemical oxidation method is reported for the synthesis of pyridine N-Oxides,which suffers from the high producting cost,high energy wastage,complex post-processing of product,heavy corrosion of devices and much wastewater.This dissertation has developed two catalytic oxidation process based on collective references for the synthesis of pyridine N-Oxides such as Titanium Silicalite-hydrogen peroxide catalytic oxidation process and Phosphomolybdic acid-hydrogen peroxide catalytic oxidation process.The optimized process parameters have been obtained to synthesize pyridine N-oxides.The main contents are as follows:Part 1:A variety of methods for the synthesis and application of pyridine N-oxides have been summarized.Part 2:Pyridine N-Oxides Titanium Silicalite-hydrogen peroxide catalytic oxidation process:pyridine and 35%H₂O₂ were used as substrates with Titanium Silicalite as the catalyst.The molar ratio between pyridine and hydrogen peroxide was 1:1.2,and the mass ratio between pyridine and catalyst was 1:0.01.They reacted at 55?for 3hours using t-BuOH as solvent.The reaction yield was 92.4%and the purity of pyridine N-oxide was 99.6%.Under the optimum condition,a variety of pyridine derivants were oxidized to the corresponding N-oxides,such as 2-methylpyridine,3-methylpyridine,4-methylpyridine,2,6-dime-thylpyridine,3-acetylpyridine,3-carbamolypyridine,4-cyanopyridine,4-methoxypyridine,2-chloropyridine,2-bromopyridine.The purity of pyridine N-oxides were 98.2-99.7%,and the yield were 26.2-87.1%,respectively.Part 3:Pyridine N-Oxides Phosphomolybdic acid-hydrogen peroxide catalytic oxidation process:pyridine and 35%H₂O₂ were used as substrates with Phosphomolybdic acid as the catalyst.The molar ratio between pyridine and hydrogen peroxide was 1:1.8,and the mass ratio between pyridine and catalyst was 1:0.02.They reacted at 60?for 3hours using t-BuOH as solvent.The reaction yield was 88.6%and the purity of pyridine N-oxide was 99.5%.Under the optimum condition,a variety of pyridine derivants were oxidized to the corresponding N-oxides,such as 2-methylpyridine,3-methylpyridine,4-methylpyridine,2,6-di-methylpyridine,3-acetylpyridine,3-carbamolypyridine,4-cyanopyridine,4-methoxypyridine,2-chloropyridine,2-bromopyridine,quinoline and2-methylquinoline.The purity of pyridine N-oxides were 98.4-99.2%,and the yield were 29.2-86.7%,repectively.In summary,two effective,simple and mild catalytic oxidation process have been developed for the synthesis of pyridine N-Oxides.The production cost,energy wastage and corrosiveness of devices were decreased and the wastewater discarge were reduced.So,these two process have great value of industrialization.