Maleic Acid → 1,1'-[4-Methoxy-1,2-phenylenebis(methylene)]bispiperidine dimaleate

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Reaction Steps

The crude diamine base (3.0 g.) was then purified by dissolution in chloroform, followed by extraction of the latter solution with ice-cold 3 N aqueous hydrochloric acid. The combined acidified aqueous layers were then basified (with the aid of ice-cooling) and the resulting organic base back extracted into chloroform, using four-100 ml. portions of the latter solvent. After drying over anhydrous magnesium sulfate and filtering, there was ultimately obtained a clear chloroform solution that was subsequently concentrated in vacuo to afford 2.0 g. of pure 1,1'-[4-methoxy-1,2-phenylenebis(methylene)]bispiperidine as the free base in the form of a pale-colored residual oil. The pure diamine oil (2.0 g.) was then dissolved in diethyl ether (200 ml.) and filtered, and the filtered solution was subsequently added to a filtered solution of maleic acid (10 g.; 0.086 mole) dissolved in diethyl ether (600 ml.) to afford a pale yellow gum as the product. Recrystallization of the latter material twice from isopropyl alcohol/diethyl ether then gave analytically pure 1,1'-[4-methoxy-1,2-phenylenebis(methylene)]bispiperidine dimaleate, m.p. 124°-126° C. The yield of pure salt amounted to 1.99 g. (9.8%).

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