Ammonium Hydroxide → 6-methyl-5-(n-propanoyl)-2(1H)-pyridinone

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C-6. 6-Methyl-5-(n-propanoyl)-2(1H)-pyridinone (and 5-Acetyl-6-ethyl-2(1H)-pyridinone)--A mixture containing 50 g of 2,4-hexanedione, 100 ml of ethanol and 50 ml of concentrated aqueous ammonium hydroxide was allowed to stand at room temperature overnight and then concentrated on a rotary evaporator at 50°-60° C. to a constant weight of 48.8 g, a pale yellow oil that solidified on standing at room temperature. The nmr spectrum of this solid in CDCl3 indicated it to be a mixture of 5-amino-4-hexen-3-one and 4-amino-3-hexen-2-one in a weight ratio of 65:35. The mixture of amino-hexen-ones was dissolved in 100 ml of dimethylformamide and treated with methyl 2-propynoate and the resulting mixture was first gently heated with stirring on a steam bath for 2 hours and then refluxed for 24 hours. The reaction mixture was allowed to cool to room temperature and allowed to stand at room temperature overnight. The crystalline material that separated was collected, washed with isopropyl alcohol and dried in vacuo at 90°-95° C. to yield 11.9 g of 6-methyl-5-(n-propanoyl)-2(1H)-pyridinone, m.p. 173°-175° C. The mother liquor was concentrated on a rotary evaporator and the residue was crystallized from isopropyl alcohol, washed with ether and dried to yield another 10.4 g of 6-methyl-5-(n-propanoyl)-2(1H)-pyridinone, m.p. 173°-175° C. (The filtrate was concentrated in vacuo to yield 57.8 g of an oily residue which was chromatographed on silica gel (700 g) using ether as eluant. Evaporation of the ether fractions yielded 22.4 g of the least polar component, an oily material, a middle fraction of 16.4 g, a viscuous gummy oil, and as the most polar component, 7.8 g, a solid which was recrystallized from isopropyl alcohol to yield a white amorphous powder, m.p. 140°-145° C., whose nmr spectrum showed it to consist of 90% 5-acetyl-6-ethyl-2(1H)-pyridinone. Six further recrystallizations of this product resulted in 1.5 g of pure 5-acetyl-6-ethyl-2(1H)-pyridinone, m.p. 162°-164° C., as shown by its nmr spectrum.)

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