Methylparaben → 4-(2-Piperidinoethoxy)benzoic acid hydrochloride

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To two 125 mL 3 neck flasks with mechanical stirring, condensers, and a heating apparatus consisting of an RTD probe in the flask hooked via a temperature controller to a heating mantle the following were added: 7.61 g of methyl 4-hydroxybenzoate, 11.05 g of β-chloroethylpiperidine hydrochloride, 16.59 g of powdered potassium carbonate, and 60 mL of amyl acetate. The flasks were placed in an ambient oil bath and heated under nitrogen to 95° C.-100° C. The reaction was allowed to proceed until HPLC indicated 8% unreacted methyl 4-hydroxybenzoate in A, 12% unreacted in B. The flasks were then cooled to less than 50° C. 40 mL deionized water was added with stirring to dissolve solids. The aqueous layer was separated and discarded. The water wash was repeated and the aqueous layer was separated and discarded. HPLC of organic layers showed 6% 4-hydroxybenzoate remains in A, 3% in B. 25 mL of 8N hydrochloric acid was added with stirring to extract the intermediate. The layers were separated and the acid layers returned to reaction flasks. The acid solutions were heated at about 95° C. for about 4 hours. The flasks were then cooled to less than 40° C. and 25 mL of acetone was added. The mixture was then cooled to 0° C.-5° C. for 1 hour. The mixture was filtered and the cakes rinsed with approximately 25 mL of acetone and dried. A=11.50 g (80.5%), B=10.5 g (73.8%)

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