The Catalytic Oxidation Of 3-Phenyl-1-propene Compounds With Molecular Oxygen

Oxidation is a very important reaction, traditional methods of oxidation generally require an equivalent amount of inorganic oxide, inorganic acid, elemental halogen, etc. which is not only expensive, but also causes great pollution to the environment. Ketone compounds resulting from the cleavage of the double-bounds of aromatic alkenes are important intermediates in organic synthesis. Therefore, exploring a mild catalytic oxidation system to oxidize the double-bound of aromatic alkene is particularly important.A series of Schiff base- metal complexes were synthesized, which served as catalysts for the catalytic oxidation of double-bond of aromatic hydrocarbon using oxygen as oxidant. Since Schiff base and porphyrin ligands have same features regarding planar structures and electrochemical properties, high-activity Salen metal complexes were chosen as catalysts for the oxidation of aromatic hydrocarbons.Using MnSalen as catalyst, the catalytic oxidation of double-bound of benzene propylene hydrocarbons, such as cinnamic acid, styrene, and cinnamic acid ethyl ester, using molecular oxygen showed a relatively mild reaction condition and high selectivity. Under optimized conditions, with oxygen as the oxidant, MnSalen catalyst, and tert-butyl hydroperoxide co-catalyst, the catalytic oxidation of styrene-acrylic olefin compound generally proceed with >99% selectivity. After optimization, the optimal condition for catalytic oxidation of styrene was 1eq. TBHP, 1 mol% MnSalen, 165°C and 0.4 MPa oxygen pressure, which reached 91% conversion rate after two hours’ reaction under mild condition. The selectivity rate can be >99% with benzaldehyde.Applying diverse Schiff base-metal complexes while using CoSalen catalyst, NHPI co-catalyst and oxygen oxidizer, benzoyl enol ethyl acetate and ethyl benzoylacetate can be generated by the catalytic oxidation of ethyl cinnamate. Finally the optimal reaction condition was obtained as 15 mL 1,4- dioxane as solvent 2.5 mol% of NHPI, 0.5 mol% of CoSalen as catalyst, reaction temperature of 120°C, and 0.4 MPa oxygen pressure. Thyl benzoylacetate and its variant benzoyl enol ethyl acetate was obtained with around 82.4% yields from the catalytic oxidation of ethyl cinnamateIn summary, several synthetic Schiff base- metal complexes were synthesized. Applying these complexes as catalysts, with oxygen as the oxidant, the styrene-acrylic olefin can be transferred into benzaldehyde directly in mild reaction conditions. The selectivity of aromatic aldehyde is good.