Br?nsted Acid Catalyzed Tert-butylation Of 3-methyl-catechol

Tert-butyl phenolic compounds,which can be synthesized through Friedel-Craftsreaction,are important in organic synthesis,industry and academia research.Hindered phenolic compounds can serve as antioxidants and important intermediates for various fine chemical products.General procedures containing Bronsted or Lewis acid as the catalysts for the synthesis of tert-butyl phenols always suffered from corrosiveness,low selectivity,separation problem,pollution or other issues.To overcome the above defects,different research groups have reported novel heterogeneous catalyst systems such as Bronsted acidic ionic liquids,solid supported acids,and ion exchange resins in recent years.Many reactions keep good selectivities and activities after recycling for several times.However,the application of those heterogeneous catalysts were hindered because of relatively complex preparing procedure,remarkable decrease in activity or selectivity during reuse and irreversible impurities produced.In this paper,t-butyl substituted 3-methyl catechols were prepared using 3-methyl catechol as the substrate and tert-butyl alcohol or isobutylene as the tert-butylation reagents.The reaction parameters,such as the catalyst,reaction temperature,the amount of tert-butyl alcohol and catalyst and the reaction time were optimized.The regioselectivity of this alkylation process could be controlled under different conditions: When the molar ratio of dodecylbenzenesulfonic acid,tert-butanol,and 3-methylcatechol is 0.6:1.1:1,5-tert-butyl-3-methyl catechol is prepared in 97% yield at 75°C;while 6-tert-butyl-3-methyl catechol is obtained in 75% yield following similar conditions except that employ PTSA as the catalyst and perform the reaction at 47 °C;3,5-di-tert-butyl-6-methyl catechol could be reached in 44% yield at 47 °C with Ts OH as the catalyst and more tert-butyl alcohol(2.0eq.).The catalyst could be recycled for 10 times without significant loss of its activity,and pure product could be easily separated from the reaction mixture through filtration in quantitative yield.