4-Hydroxybenzoic Acid → 4-hydroxy-benzoic acid, compd. with (2S,4E)-N-methyl-5-[5-(1-methylethoxy)-3-pyridinyl]-4-penten-2-amine (1:1)

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Reaction Steps

p-Hydroxybenzoic acid (2.62 g, 19.0 mmol) was added in portions to a stirred solution (2S)-(4E)-N-methyl-5-(5-isopropoxy-3-pyridinyl)-4-penten-2-amine (4.79 g of 93% pure, 19.0 mmol) in isopropyl acetate (50 mL). During the addition, crystallization of salt was evident. After complete addition of the p-hydroxybenzoic acid, the suspension was heated near its boiling point as isopropanol was slowly added. After 15 mL of isopropanol had been added, complete dissolution was obtained. Cooling of the solution to ambient temperature (overnight) resulted in deposition of a crystalline mass, which was collected by suction filtration and air dried (4.03 g). A second crop (0.82 g) was isolated from the concentrated filtrate, by addition of acetone. The two crops of crystals were combined and recrystallized from acetone (50 mL). The solid was collected by suction filtration and dried in the vacuum oven (50° C.) for 18 h. This left 4.24 g (60.0%) of white crystals (98+% pure by both GCMS and LCMS; m.p. 99-101° C.).

Provenance & Evidence