The Studies Of Transition-Metal-Free System Catalyzed Aerobic Oxidation Of Sulfides And Alcohols

The selective oxidations of sulfides to sulfoxides and alcohols to aldehydes or ketones are both momentous functional group conversion reactions, which are of important significance in the development of green, mild, efficient and selective oxidations. It is much accounted for the economical and environmentally friendly feature by the use of moleculer oxygen (air) as the oxygen source for the oxidation. This research has overcome the shortcoming brought by the use of transition metal, and methods for the green, mild, efficient and selective aerobic oxidations based on transition-metal free catalysts has been developed.Firstly, the system of transition-metal free aerobic oxidation catalysts has been developed with NaNO2as the oxygen activator, and Br2/NaNO2/O2was adapted for investigation of selective oxidation of sulfides to sulfoxides. With thioanisole as the model substrate translated into sulfoxide, the100%conversion rate of thioanisole and96%production yield of methyl phenyl sulfoxide were obtained in the condition of0.015mL Br2(mole ratio3x) and0.0345g NaNO2(mole ratio5x) at room temperature and atmosphere pressure. Based on the previous research, another oxidation system of DBDMH/NaNO2/O2was designed by substitution of1,3-dibromo-5,5-dimethylhydantoin (DBDMH) for Br2as a class of more efficient bromine source. The effect of reaction parameters such as catalyst dosage, reaction temperature, reaction time and reaction pressure was investigated. Finally, the conversion rate100%and the production yield95%were obtained, when0.0572g DBDMH (mole ratio2x),0.0345g NaNO2(mole ratio5x),1MPa,100℃and1h were conducted as the optimum reaction parameters. A number of substrates with different function groups were inspected by the oxidation systems described above. The result indicated that substrates which contain electron-donating groups were more easily converted into sulfoxides than those contain electron withdrawing groups. The products were identified by IR,1H NMR,13C NMR and MS after separation, and the mechanism was studied also.Secondly, two transition-metal free catalysts aerobic oxidations were developed with TBN as the oxygen activator, and selectivity of HBr/TBN/O2catalytic system was investigated. Thioanisole was still used as the model substrate. For the system HBr/TBN/O2, substrate translated into sulfoxide by the conversion rate100%in the condition of0.03mL40%HBr (mole ratio5x),0.04mL TBN (mole ratio3x), for the other one, substrate translated into sulfoxide by the conversion rate100%in the condition of0.0572g DBDMH (mole ratio2x), 0.05mL TBN (mole ratio4x) under the pressure0.8MPa and the temperature50℃. Different substrates had been tested by the two systems above and the products were identified by IR,1H NMR,13C NMR and MS.Thirdly, transition-metal free catalysts alcohols selective aerobic oxidation system TEMPO/TBN/O2was set up with TEMPO and TBN as the oxygen activator. The orthogonal experiment has been designed in order to investigate the effect of the catalyst dosage, reaction time, oxygen pressure and the reaction temperature in aqueous solution. The best reaction condition is:1mol%TEMPO and1mol%TBN under80℃and the oxygen pressure0.1MPa for1hours, by which the conversion rate of benzyl alcohol can reach to100%and the yield of benzaldehyde is96%. Under the condition of room temperature and atmospheric pressure, the selective catalytic oxidation of alcohols can be carried out in this system. But the dosage of catalyst and the reaction time should be increased. Further, the oxidations of alcohols with N-contained heteroatom functional group, aromatic alcohol, fatty primary alcohol or fatty secondary alcohol to aldehydes or ketones correspondingly were studied. The conversion rate of alcohols reached100%and the production yield of aldehydes or ketones reached93%-98%. The mechanism related has been discussed.Fourthly, the transition-metal free catalysts aerobic oxidation with PSB-TEMPO-NOx as the oxygen activator has been set up. PSB-TEMPO was obtained by bonding4-oxo-TEMPO to porous silica bead (PSB). After NOx was adsorbed in the pores of PSB, the preparation of the catalyst PSB-TEMPO-NOx was finished. It could successfully catalyzed1mmol benzyl alcohol oxidation under the dosage0.5g in4hours. The results indicated that different fatty alcohols, aromatic alcohols and heterocyclic alcoholic compounds containing O were suit for this system, and can converted into corresponding aldehydes or ketones efficiently and selectively. However, it showed activity after been used10times. The reaction mechanism was conjectured by element analysis, IR, nitrogen adsorption-desorption, NOx programmable heating desorption, TEM and XRD.