Studies On Selective Oxidation Of Alcohols Catalyzed By TEMPO

The selective oxidation of alcohols to the corresponding aldehydes or ketones is a fundamental reaction in organic synthesis and plays a central part in industrial production. Recently,of particular interest are the use of molecular oxygen and air,which have several benefits,including low cost,improved safety,abundance,and water as the sole byproduct. In this dissertation,valuable explorations have been carried out on selective oxidation of alcohols to corresponding aldehydes and ketones using molecular oxygen as primary oxidant.The ionic liquid immobilized TEMPO(TEMPO-IL)was prepared and used in TEMPO-IL/CuCl catalytic system,which was applied for the aerobic oxidation of alcohols using[bmim]PF₆ as solvent or under solvent-free conditions.The system exhibits favorable catalytic activity for benzylic and allylic alcohols,whereas in the case of heterocyclic and aliphatic alcohols the catalytic activity is poor even even after prolonged reaction time.The catalytic system was easily recovered and reused in the reaction.In the case of the oxidation of benzyl alcohol,the catalyst was recovered and reused for 5 times with no significant loss of catalytic activity.The catalytic mechanism of TEMPO-IL/CuCl was discussed.To improve the catalytic activity of TEMPO/CuCl,base promoted alcohol oxidation was studied.It was found that most inorganic and organic bases speed up the reaction except sodium bicarbonate,and the promotion effect of pyridine,N-methylimidazole and ethanol solution of sodium hydroxide was remarkable.Because of the loss of TEMPO and base in the extraction process,the TEMPO/CuCl/pyridine system can not be recycled and reused. TEMPO-IL and 3A molecular sieve(MS3A)were used to replace TEMPO and base respectively.The TEMPO/CuCl/3AMS catalytic system also have similar reaction with the TEMPO/CuCl/pyridine system,and the catalyst can be easily recovered and reused.The aerobic oxidation of alcohols can be achieved by TEMPO/CuCl catalytic system in water,in spite of the low conversion and selectivity.With the addition of base and surfactant, the conversion and selectivity can be improved.The recycling of ionic liquid and silica immobilized TEMPO was investigated.Because of the break of the bond between TEMPO and supporter,the recycling of the catalytic system was difficult.