(1) Hydroquinone route
Using hydroquinone and tert-butanol, using phosphoric acid as a catalyst, in 101. The neutral form of tert-butylhydroquinone was prepared by reacting at C, and then tert-butylhydroquinone and dimethyl sulfate were heated and refluxed for 18 hours in a nitrogen atmosphere. After cooling, they were extracted with benzene. The liquid is washed with hot water, and benzene is evaporated to remove the crude product, which is then distilled under reduced pressure to obtain butylhydroxyanisole.
(2) Parachlorophenol route
Using parachlorophenol as raw material, mix it with isobutylene and react in the presence of phosphoric acid. The obtained product is a mixture of 4,2~CI(Me.OC.H.OH and 4,2,6-C1(Me.C):C.H.OH. The former reacts with CH.ONa in a methanol solution. , the product 3-BHA is obtained,
(3) p-methoxyphenol route
The key to the synthesis of p-methoxyphenol lies in the combination of tert-butyl group and benzene ring, so The choice of condensation catalyst is the most important. Earlier processes used protonic acids as catalysts, such as concentrated sulfuric acid, phosphoric acid, hydrofluoric acid, etc., but the reaction conditions were harsh and required high temperatures. According to Japanese patent reports, ion exchange was used. The resin is used as the catalyst, the reaction temperature is 65-75°C, the total yield can reach 68.5%, of which the 3-BHA content is 51.8%, and the 3-BHA in the obtained product is 90%, according to another Japanese patent report. The content of 3-BHA is as high as 82.3%, and the conversion rate of p-methoxyphenol is 87%, which cannot be achieved by ordinary inorganic acid catalysts.
(4) Para-aminoanisole route.
First synthesize p-hydroxyanisole, p-methoxyphenol, and then prepare BHA through alkylation reaction. The specific process is as follows: under stirring in an ice bath, add p-aminoanisole and methoxyphenol. Sodium nitrate (molar ratio 1:1.15) is used for diazotization reaction in the presence of sulfuric acid. After the reaction is completed, it is filtered with insulation and the filtrate is added dropwise to the hot hydrolysis reaction solution for hydrolysis to generate p-hydroxyanisole. It can be stripped with steam, and the condensed p-hydroxyanisole solution is extracted with an organic solvent. After concentration and distillation to remove the solvent, p-hydroxyanisole can be obtained with an average yield of 84.7%.
(5) Parahydroxyanisole route
Heat and dissolve parahydroxyanisole, tert-butanol and solvent, then add this mixed reagent to the preheated catalyst, and mix well The reaction is carried out in the reactor, and the reaction is completed after 15 minutes. Take a sample and measure the unreacted tert-butanol by high-performance liquid chromatography. When the sampling test result is qualified, the reaction can be stopped and the organic matter is collected and removed by distillation. The organic solvent was distilled under high vacuum and reduced pressure to obtain BHA product with a yield of 77.8%.