The present invention provides a catalyst for synthesizing a cyclic carbonate and a preparation method and use thereof. A diamine compound X, a salicylaldehyde-containing compound and a metal source M are subjected to reaction, and then added with a phenothiazine compound Y for continuous reaction to obtain a phenothiazine metal Schiff base catalyst. The formation of phenothiazine free radicals by phenothiazine compounds with a central metal can protect the central metal in the course of reaction and inhibit inactivation caused by the self-polymerization of the central meta, thus improving the activity and stability of a catalyst. Phenothiazine compounds can be present as a polymerization inhibitor to inhibit the generation of by-products such as polycarbonates and polyethylene glycol and enhance the selectivity of the catalyst during the reaction. The phenothiazine compounds are alkaline and can adsorb and activate carbon dioxide during reaction, which helps to improve the reaction efficiency. The phenothiazine metal Schiff base catalyst prepared in the present invention has high activity, strong stability and good selectivity and thus, can achieve the efficient catalyzed synthesis of cyclic carbonates under mild conditions.

Disclosed are processes for preparing 5-bromo-3,4-dimethylpyridin-2-amine and 6-bromo-7,8-dimethyl-[1,2,4]triazolo[1,5-a]pyridine: (I), (VI).

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A catalyst composition process for olefin oligomerization is provided. The catalyst composition includes a chromium compound, wherein the chromium compound has at least one substituted or unsubstituted phosphate ligand, a ligating compound, and a cocatalyst. The catalyst composition for olefin oligomerization of the disclosure includes a specific chromium compound (such as a chromium-containing phosphate compound).

Methods, systems, and compositions for oxidation are provided. The method comprises combining a macrocyclic ligand and metal complex catalyst, an electrolyte, the substrate, and water to form an aqueous composition. The method comprises applying an electrical voltage to the aqueous composition and oxidizing the substrate in the presence of the catalyst.