Preparation Of Heterogeneous Catalyst TEMPO/CPS And Its Catalytic Propertyin Molecular Oxygen Oxidation Of Alcohols

The selective oxidation of alcohols to the corresponding aldehydes or ketones is one of the most important functional group transfer process in organicsynthesis, occupies very important position in fine chemical production. However, most alcohol oxidation methods currently used existence some problems, such as, harsh reaction condition and reaction process to produce a large number of environmental pollutants. So development of green environmental and economicmolecular oxygen oxidation technology is attracted to wide attention, and the oxidation catalysis system of 2,2,6,6-tetramethyl-piperidinyl-1-oxy(TEMPO) which has a high catalytic activity was used as catalyst and molecular oxygen as oxidation get a strong develop. Meanwhile, to come true the cycle apply of catalyst, achieve the immobilization of TEMPO, make homogeneous catalysis to heterogeneous is one of the major direction of the green chemistry. Though molecular design, this study used the crosslinked polystyrene microspheres(CPS) as the supporter, though the simple polymer reaction to achieve the immobilization of TEMPO, and solid catalysts TEMPO/CPS was preparation successfully. Then catalysts microspheres were combined with transition metal compounds, and combinational catalysts were constituted. The combinational catalysts were used in the oxidation process of cinnamyl alcohol and 1-phenyl ethanol with molecular oxygen as oxidant. The catalytic properties and catalytic mechanisms of the different co-catalyst were investigated in depth, valuable results are obtained. Obviously, this research to promote green catalytic oxidation has obvious scientific significance and important application value in the field of organic synthesis.In this work, the anhydrous aluminium trichoride(AlCl3) was selected as Lewis catalyst and chlorobutyryl chloride(CBC) was used as acylation reagent, though the Friedel-Craftsacylation reaction between CBC and the benzene ring of CPS microspheres surface, achieved the microspheres CB-CPS which containing chlorobutyryl in surface. Then 4-hydroxy-2,2,6,6-tetramethyl-piperidinyl-1-oxy(4-OH-TEMPO) was used as nucleophilic reagent reacted with the halogen alkyl group of CB-CPS microspheres to realize the immobilization of TEMPO, and the heterogeneous catalyst microspheres TEMPO/CPS were obtained successfully. Infrared spectrum(FT-IR), scanning electron microscope(SEM) was used to characterizethe chemical structure of TEMPO/CPS microspheres. The influence of main factors on the Friedel-Craftsacylation reaction was investigated. The experimental results show when AlCl3 was used as the Lewis acid catalyst, chloroform as suitable solvent, and response for 5 h at 75 ℃, the microspheres of CB-CPS was obtained which the bonding amount of chlorinated butyl acyl bond was 2.84 mmol/g, then get the solid catalyst microspheres TEMPO/CPS which solid loads of TEMPO was 1.78 mmol/g.Immobilized microspheres TEMPO/CPS was used as dominated catalyst, then TEMPO/CPS was combined with two kinds of transition metal compounds, for which one group contains high valence state metal ion with weaker oxidizability than NO3- ion, and for another group the corresponding high valence state metal ion has stronger oxidizability than NO3- ion, and combinational catalysts were constituted. The combinational catalysts were used in the oxidation process of cinnamyl alcohol with molecular oxygen as oxidant. The catalytic properties and catalytic mechanisms of these combinational catalysts were investigated in depth. The study results indicate that the some combinational catalysts constituted by some transition metal salts with TEMPO/CPS microspheres could effectively catalyze the oxidation reaction of cinnamyl alcohol to cinnamyl aldehyde as sole product. When the transition metal nitrate salt was used asco-catalysts, if the corresponding high valence state metal ion has weaker oxidizing ability than NO3- ion, for example, Fe(NO3)3 and Cu(NO3)2, the positive and negative ions will work together in the catalytic process. If the oxidizability of the corresponding high valence state metal ion is stronger than NO3- ion, for example, Co(Ⅲ) and Mn(Ⅲ) ions corresponding to Co(NO3)2 and Mn(NO3)2, the metal ion will alone play a role of the co-catalyst and NO3- ion does not work. So Co(NO3)2 and Co(OAc)2 or Mn(NO3)2 and Mn(OAc)2 have same co-catalyst properties. The experimental results show that among several transition metal salts, Fe(NO3)3 is the best co-catalyst, and under mild conditions(at 55 ℃ and with O2 at ordinary pressure) cinnamyl alcohol can be highly effectively transformed into cinnamyl aldehydewith aconversion of 92 %. The suitable solvent is ethyl acetate and the suitable molar ratio of the main catalyst TEMPO/CPS to the co-catalyst Fe(NO3)3 is 1:1.2, when the content of TEMPO in dominated catalyst is proportion to 11 mol% for substrate, the catalyst result is best.The combinational catalysts which were constituted by TEMPO/CPS and transition metal compounds were used in the oxidation process of 1-phenyl ethanol with molecular oxygen as oxidant. The catalytic properties and catalytic mechanisms of these combinational catalysts were investigated in depth, and theinfluence of main reaction conditions of oxidation wasinvestigated. The study results indicate that the transition metal nitrate salt was used asco-catalysts, if the corresponding high valence state metal ion has weaker oxidizing ability than NO3- ion, the positive and negative ions will work together in the catalytic process. If the oxidizability of the corresponding high valence state metal ion is stronger than NO3- ion, the metal ion will alone play a role of the co-catalyst and NO3- ion does not work. The experimental results show that among several transition metal salts, Fe(NO3)3 is the best co-catalyst, and under mild conditions(at 55 ℃ and with O2 at ordinary pressure) 1-phenyl ethanol can be highly effectively transformed into acetophenonewith aconversionof 96 %. The suitable solvent is acetic acid and the suitable molar ratio of the main catalyst TEMPO/CPS to the co-catalyst Fe(NO3)3 is 1:1.2, when the content of TEMPO in dominated catalyst is proportion to 11 mol% for substrate, the catalyst result is best. The TEMPO/CPS catalyst has excellentre cyclability.