Method of synthesizing 2-alkoxyl-4-methylphenol with 2-bromine-4-methylphenol

Abstract

The invention provides a method of synthesizing 2-alkoxyl-4-methylphenol with 2-bromine-4-methylphenol. The method comprises the step of allowing alkyl sodium alkoxide to react with 2-bromine-4-methylphenol in the presence of alkanol and in a near-critical state of alkanol. According to the method, a reaction condition of alkanol in the near-critical state is adopted; a catalyst and a promoter are substituted for catalyzed synthesis of 2-alkoxyl-4-methylphenol; the method is a green reaction technology; alkanol can be recovered in a simple distillation manner after reaction; an atom utilization ratio is higher; a conversion rate of the reactor, 2-bromine-4-methylphenol, can reach above 97.9% and 100% at most; and the selectivity of the product, 2-alkoxyl-4-methylphenol, can reach above 93.4%.

Description

technical field [0001] The invention relates to a method for synthesizing 2-alkoxy-4-methylphenol from 2-bromo-4-methylphenol in a near-critical state, belonging to the field of fine chemicals. Background technique [0002] 2-methoxy-4-methylphenol, also known as 4-methylguaiacol (2-Methoxy-4-Methyl Phenol, C 8 h 10 o 2 , Molecular weight: 138.16, CAS number: 93-51-6), is a colorless liquid, is an important spice, and is also an intermediate of many medicines and spices, especially an important intermediate for the synthesis of vanillin. Vanillin is a broad-spectrum spice widely used in food industry, pharmaceutical industry and organic synthesis. At present, the more advanced route of synthesizing vanillin on an industrial scale is to obtain 4-methylguaiacol by bromination and remethoxylation of p-cresol, and finally oxidize to obtain vanillin. Among them, the conversion rate and yield of 4-methylguaiacol prepared by alkoxylation are high, the pollution is small, and th...

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Problems solved by technology

[0011] CN101417931A discloses a synthetic method of ethyl vanillin and its derivatives, which includes the use of alkaline earth metal oxides instead of sodium alkyl alkoxide as an alkoxylation agent, but a large amount of promoter polar aprotic solvent is used for the reaction , difficult to recycle

[0012] CN101774897A discloses a preparation method of vanillin and its analogues. When the method is carrying out alkoxylation reaction, methyl formate or CO is used to replace the polar aprotic solvent as a cocatalyst, although the polar aprotic solvent can be solved. The solvent is difficult to recover, but the overall yield is low, and there is still a certain distance for industrial production

[0013] The above prior art documents have adopted sodium alkyl alkoxide as the alkoxylation reagent, and copper salt is the main reaction catalyst, and some have used polar aprotic solvent as cocatalyst, and polar aprotic solvent is under strong alkaline condition It breaks down easily and is difficult to recycle

Some use CO 2 , methyl formate, CO, etc. instead of polar aprotic solvents as cocatalysts, but the yield is low and it is difficult for industrial production

[0014] The main problems of the alkoxylation of the above inactive brominated aromatic compounds are: (1) the reduction reaction of debromination will occur in the reaction process, and the reaction selectivity needs to be improved; (2) the methoxylation reaction cannot be quantitatively thorough The product needs to be separated from the raw material by rectification; (3) ethoxylation and higher-level alkoxylation cannot be effectively implemented, and the conversion rate and yield are greatly reduced; (4) the use of dimethyl Formamide is as solvent or co-catalyst, and dimethyl formamide is easy to decompose in reaction process, and remainder recovery is also more difficult; (5) if use carbon dioxide or methyl formate as co-catalyst, reaction is not thorough enough under enlarged scale; ( 6) Using copper salt as a homogeneous catalyst, recovery is difficult, the operation is extremely complicated, and the utilization rate of atoms is not high

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