Novel process for synthesizing high-steric-hindrance bromobenzene

Abstract

The invention relates to a novel process for synthesizing high-steric-hindrance bromobenzene. A preparing method of aryl bromide includes the steps of conducting reaction on aniline hydrobromide and inorganic nitrite in a two-phase or multi-phase system formed by water and one or more inert solvents in the presence of an additive with the pH value smaller than 7, and conducting reaction on ortho-single-substitution or double-substitution high-steric-hindrance aniline hydrobromide and directly-added inorganic nitrite to be converted into corresponding bromobenzene. By means of the process, thecatalysis of heavy metal salt is not needed, no alkyl nitrite intermediate needs to be separated, no diazonium salt or a solution of diazonium salt needs to be separated, after-reaction treatment is completed through conventional methods of water adding, phase separating, rectifying and the like, a small amount of aromatic phenol generated in the reaction can be washed away through alkaline water,and the novel process is suitable for industrial production.

Description

technical field [0001] The invention relates to the technical field of fine chemicals, in particular to a new process for synthesizing brominated benzene with high steric hindrance. Background technique [0002] It is well known that highly sterically hindered bromobenzenes are key intermediates of 2-aryl-malononitriles (eg WO2004050607) or phenyl-substituted acetoacetates (eg Tetrahedron Letters 45, pages 4261-4264 (2004), both of which The compounds are key intermediates of acaricides (eg DE4216814), insecticides (eg WO199805638), and herbicides (eg WO200480962, WO199947525, WO200078881). [0003] Usually the synthesis of aryl halides is accomplished by diazotization of the corresponding arylamine followed by decomposition of the diazonium salt (Sandmeyer reaction). In general, no catalyst is needed in the reaction for aryl iodides (eg Organic Syntheses, Coll. Vol. 2, page 351), while for the formation of aryl chlorides and aryl bromides, the reaction usually requires Ca...

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Problems solved by technology

[0004] The presence of steric hindrance at the ortho position reduces the selectivity of the Sandmeyer reaction and often leads to the corresponding phenol becoming the main product. Therefore, in the P1 example of patent WO2000078712, 1-bromo-2,6-diethyl The yield of base-4-methylbenzene is 71%, while in embodiment P9, the yield of 1-bromo-2,6-diethyl-4-methylbenzene is only 44%. In patent WO2006084663 describes a method for the synthesis of 1-bromo-2,6-diethyl-4-methylbenzene in approximately 90% purity by adding alkyl nitrites to the reaction organic solvent system in crude yields of approximately It is 83-90%, but this method has its disadvantages. The alkyl nitrite is unstable, and its handling method is dangerous, and the alkyl nitrite needs to be prepared separately. In addition, the 1- The purity of bromo-2,6-diethyl-4-methylbenzene is difficult to improve, because the product of this method contains not only 2,6-diethyl-4-methylphenol, but also the corresponding ether compound , such as isopentyl-2,6-diethyl-4-methylphenyl ether, the boiling point of this type of ether compound is close to that of the product, and it is difficult to separate it by rectification

[0005] Patent WO2010102761 describes another synthesis process. In this process, an aqueous solution of iron ion or ferrous ion salt is used as a catalyst for the Sandmeyer reaction. The crude yield of the reaction can reach 73-90%, but this process requires a separate Synthesis of diazonium salts, as we all know, the synthesis and treatment of such dangerous diazonium salts requires not only a strong freezing system, but also a highly diluted aqueous phase system, which will lead to a large amount of wastewater

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