Study On The Preparation Of Corresponding Carbonyl Compounds By Catalytic Oxidation Of Fluorene And Benzyl Alcohol With Molecular Oxygen

Aromatic carbonyl compounds have important uses and are widely used as intermediates in organic chemical industry.Catalytic oxidation is one of the most important methods for the synthesis of aromatic carbonyl compounds.The inorganic oxidants,such as Potassium Permanganate,are still being used in large quantities,and a large amount of waste residue has been produced.Therefore,the development of green synthesis of aromatic carbonyl compounds is of great significance.Molecular oxygen is cheap and easy to obtain.The by-product of oxidation reaction with molecular oxygen is water.As a green and clean oxidant,it attracts more and more attention.In this paper,fluorene and benzyl alcohol are selected as the representative compounds,and molecular oxygen is used as oxidant to develop a new system of high efficient catalytic oxidation.Our purpose is to study the activation oxidation of aromatic side chain C-H,and to synthesize the corresponding carbonyl fluorenone and benzaldehyde.In this paper,a new phosphate catalyst was developed to replace the traditional potassium hydroxide and other strong bases,and a new system for the preparation of fluorenone was established by using molecular oxygen as the oxygen source.With 5 mol%potassium phosphate as a catalyst,dimethyl sulfoxide as solvent,70?,3 h,and atmospheric oxygen,the fluorene was completely converted and the selective of fluorenone was>99%.The effects of different solvents on the reaction were investigated,in which the catalytic activity was higher in the dipolar solvent?such as dimethyl sulfoxide and N,N-Dimethylformamide?.There was a positive correlation between the conversion rate of fluorene and the dielectric constant of the solvent in the commonly used solvents investigated.The oxidation process of fluorene was investigated by means of in situ infrared spectroscopy.In order to make the catalyst easy to separate and recycle,we prepared K₃PO₄/Al₂O₃ supported catalysts.We found that water was not the cause of K₃PO₄/Al₂O₃ inactivation.This paper provides a reference for the oxidation of methylene over side chain of benzene rings and a new idea for the application of phosphate.In the process of oxidation of benzyl alcohol,the assumption that two benzyl ether was formed and then oxidized to benzaldehyde was proposed in the oxidation of benzyl alcohol by oxidation of benzyl alcohol as a model reaction with the difference in the energy of C-H bond linked to oxygen in the molecules of alcohol and the corresponding ether molecules.A new system was developed for the catalyst of p-toluene sulfonic acid and copper nitrate under solvent free conditions,and the catalytic activity of different acids,nitrates and copper salts were investigated.With 15 mol%p-toluene sulfonic acid and 5 mol%copper nitrate as catalysts,100?,1 h,and atmospheric oxygen,benzyl alcohol was completely converted and the selective of benzaldehyde was 96%.The possible reaction path of benzyl alcohol to benzaldehyde under the action of copper nitrate and toluene sulfonic acid was verified by the experiment on the separate action of the catalyst component and the path of benzyl ether as the substrate.The catalytic oxidation of benzyl alcohol to benzaldehyde was achieved by using p-toluene sulfonic acid and copper nitrate as catalysts without solvent.The reaction path from alcohol to ether to aldehyde provides a theoretical reference for other oxidation reactions,without the use of solvents in accordance with the principle of green chemistry.