2.4- dimethyl-3-acetylpyrrole

Pivalaldehyde added at 35° to a soln. of 2,4-dimethyl-3-acetylpyrrole in HI and acetic anhydride containing hypophosphorous acid, and stirred 10 min. 2,4-dimethyl-3-acetyl-5-neopentylpyrrole. Y 93%. F. e., also isocyclics, and reagents s. B. V. Gregorovich et al.. Can. J. Chem. 46, 3291 (1968). 

To 9.5 g of 3-acetyl-2,5-hexanedione in 50 ml of benzene, 7.7 g of p-chloroaniline are added and the mixture is refluxed for 5 h with azeotropic removal of the water formed. The excess solvent is evaporated and residue is vacuum stripped 12.0 g (yield 80%) of l-p-chlorophenyl-2,5-dimethyl-3-acetylpyrrole as an orange oil which rapidly crystallizes are thus obtained, boiling point 144°-146°C. Melting point of it 80°-81°C (recrystallization from hexane). 

To 5.0 g of the l-p-chlorophenyl-2,5-dimethyl-3-acetylpyrrole, 0.7 g of sulfur and 2.7 ml of morpholine are added and the mixture is refluxed for 5 h. Then, 20 ml of an aqueous solution of 20% are added and the mixture is refluxed for 4 h. The mixture is washed with ether, acidified with 20% HCI, and then extracted with ether. The organic phase is extracted with a 10% sodium bicarbonate solution which is acidified with 5% HCI. The solid obtained is filtered and recrystallized several times from a diethyl ether-pentane mixture. 1.1 g (yield 20%) of l-p-chlorophenyl-2,5-dimethyl-3-pyrroleacetic acid are thus obtained, melting point 100°-103°C. 

In the presence of sulfur compounds (e.g. cysteine) pentoses and methylpentoses produce, in addition to 4-hydroxy-5-methyl-2H-furan-3-one and 4-hydroxy-2,5-dimethyl-2ff-furan-3-one, respectively, related compounds containing sulfur in the molecule. Many of these compounds resemble the aroma of cooked or roasted meat. In the presence of primary amines, 1-deoxyhexo-2,3-diuloses derived from disaccharides yield pyridinium betaines and, further, pyrid-4-ones and isomeric 2-acetylpyrroles. The reaction with secondary amines leads to N-substituted... 

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