Question

Consider the following compound: 3,5-dimethylphenol. Using the protecting group strategy, propose a synthetic route for converting 3,5-dimethylphenol to 3,5-dimethylbenzoic acid. Include all necessary reagents and reaction conditions.

Answer 1

To convert 3,5-dimethylphenol to 3,5-dimethylbenzoic acid, we can use the following synthetic route:1. Protect the phenol group:Reagent: tert-Butyldimethylsilyl chloride  TBDMSCl , imidazoleSolvent: Dry dimethylformamide  DMF Temperature: Room temperatureDuration: 2-4 hoursThis step will protect the phenol group by converting it to a tert-butyldimethylsilyl ether, which is stable under a variety of reaction conditions.2. Oxidation of the methyl group to a carboxylic acid:Reagent: Potassium permanganate  KMnO4 Solvent: Aqueous solution  water Temperature: Room temperatureDuration: 2-4 hoursThis step will oxidize the methyl group at the para position to the phenol group to a carboxylic acid, forming the desired 3,5-dimethylbenzoic acid with a protected phenol group.3. Deprotection of the phenol group:Reagent: Tetra-n-butylammonium fluoride  TBAF Solvent: Tetrahydrofuran  THF Temperature: Room temperatureDuration: 1-2 hoursThis step will remove the tert-butyldimethylsilyl protecting group, regenerating the phenol group and yielding the final product, 3,5-dimethylbenzoic acid.Overall, the synthetic route is as follows:3,5-dimethylphenol -- TBDMSCl, imidazole, DMF --> 3,5-dimethylphenol-TBDMS -- KMnO4, H2O --> 3,5-dimethylbenzoic acid-TBDMS -- TBAF, THF --> 3,5-dimethylbenzoic acid