3,5-Dihydroxybenzoic Acid → Benzoic acid, 3,5-dihydroxy-, ethyl ester

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Reaction Steps

Synthesis of monomers was achieved from 3,5-dihydroxybenzoic acid or 3,5-dihydroxybenzyl alcohol as shown in above scheme. Commercially available 3,5-dihydroxybenzoic acid 1 was dissolved in ethanol along with catalytic amount of concentrated sulfuric acid and refluxed for 12 h to obtain ethyl-3,5-dihydroxybenzoate 1a. The ester 1a was then treated with one equivalent of alkyl halide to afford the mono alkylated ester 3 and 4. The yield of this reaction was rather low, because of the disubstituted byproduct obtained in the reaction along with the product as a statistical mixture. Compounds 3 and 4 were then reduced using LiAlH4 in dry THF under ambient temperature to give the monoalkylated phenols 3a and 4a. Compounds 2a and 5a were prepared by the reaction of 3,5-dihydroxybenzyl alcohol with 1 equivalent of alkyl halide under alkylation conditions. The phenols 2a-5a were then treated with tert-butylbromoacetate and sodium iodide to give compounds 2b-5b, which upon oxidation by PCC afforded the corresponding aldehydes 2c-5c. Treatment of aldehydes with methyl triphenylphosphonium bromide and potassium tert-butoxide under THF afforded the monomers 2d-5d. Polymers 2e-5e (n>1) was synthesized by nitroxide mediated living polymerization, using unimolecular intiator. The polymers were then hydrolyzed using potassium hydroxide as the base to afford carboxylic acid polymers 2f-5f.

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