Research On Synthesis And Properties Of Heterocyclic Phenothiazine Antioxidants

Phenothiazine derivatives are widely used in various fields. They can be used as lubricating oil antioxidant,livestock anthelmintics, fruit pesticide. Otherwise, they can also be used for the synthesis of pharmaceuticals, dyes, moreover, they can become auxiliaries during the synthesis process. In recent years, the application of phenothiazine derivatives in the field of lubricating oil additives and biopharmaceutical field is more prominent and popular.In this paper, phenothiazine and its derivatives was studied from four aspects as follows:The classic synthesis method of Phenothiazine(160) is vulcanization cyclization of diphenylamine by catalysts. When the catalyst is Iodine, the improved purification process are as follows. Firstly, activated carbon decolorization was under reflux. Secondly, toluene was used to wash the crude product with stirring at room temperature for 2.5 h, collect filter cake, otherwise, the operation was repeated twice. The optimized conditions are as follows, m(activated carbon)=m(crude product)*6.25%, m(toluene)≈m(crude product)*5.2. When the catalyst is a novel solid acid, the optimized conditions are as follows. The molar ratio of diphenylamine to sulfur is 1.00:1.25, the solid acid catalyst D accounts for 25.0wt% of diphenylamine, reaction time is 6 hours.3,7-bis-(1-methyl-1-phenylethyl)-10H-Phenothiazine(165) and 3,7-bis(1,1,3,3-tetramethybutyl)-10H-Phenothiazine(166) were one pot synthesis in solvent-free conditions.The synthetic products were determined and characterized by the melting point, purity test, FT-IR, 1H-NMR, 13C-NMR, MS. The characterization results above confirm that the products are respectively160, 165, 166 which are target structures.Finally, the antioxidant properties and thermal stability of DPA, YP011, YP013, 160, 165, 166 were tested by PDSC and TG. The results show that the thermal stability of phenothiazine products have been greatly improved than the corresponding diphenylamine raw materials. Compared with 160, 165 and 166 can be used in high temperature working conditions. When the added amount is 0.0076 mmol/g in the base oil YuBase6, the oil sample containing 160 shows better antioxidation performance. But never mind, 165, 166 have good oil solubility. When the adding dosage is increasing, the oil samples adding 165, 166 shows better antioxidation performance. These provide references for their use in lubricating oil at high temperature.