Maleic Acid → Pyridine-2,3-diyl-dimethylenebis(1,1'-piperidine) dimaleate

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Reaction Steps

The above crude product was then chromatographed over silica gel, using 25 g. of said siliceous material of 70-230 mesh size and eluting with 25 ml. fractions of ethyl acetate. In this manner, there was obtained 541 mg. of slightly impure product isolated in fraction Nos. 4-13. A second chromatography run was then made on the latter (i.e., partially purified) material, using 16 g. of silica gel of 70-230 mesh size and eluting this time with an ethyl acetate/triethylamine (9:1 by volume) mixture by taking 10 ml. fractions. The pure triamine was isolated in fractions Nos. 1-2 and these were subsequently combined to afford 358 mg. (13%) of pure pyridin-2,3-diyl-dimethylenebis(1,1'-piperidine) as the free base. Conversion of the latter triamine base compound to the corresponding crystalline hydrated dimaleate salt was then accomplished in the usual manner by treatment with excess maleic acid dissolved in diethyl ether, followed by recrystallization of the isolated salt product from isopropyl alcohol to give analytically pure pyridine-2,3-diyl-dimethylenebis(1,1'-piperidine) dimaleate 0.25 hydrate, m.p. 166°-167° C.

Provenance & Evidence