Picrolonic acid, methylation

Analytical applications of pyrazolones have been reviewed by Busev et al. (65RCR237). Organic bases are easily characterized by formation of highly crystalline salts with picrolonic acid (l-(4-nitrophenyl-3-methyl-4-nitro-5-hydroxypyrazole). The last-named compound is used as a reagent for alkaloids, tryptophan, phenylalanine and for the detection and estimation of calcium (B-76MI40404). 

As expected, heterocyclic enols and potential enols (i.e, compounds existing mainly in the CH form) behave toward diazomethane similarly to the open chain and isocyclic enols, i.e. they form enol methyl ethers by reactions of the SnI type (cf. footnote 29). Examples of this behavior are barbituric acid, picrolonic acid, dchydroacetic acid (64), 3-methyl-l-phenylpyrazolin-5-one, 1-phenylpyrazoli-dine-3,5-dione, 1,2-diphenylpyrazolidine-3,5-dionc, 3-hydroxy-... 

Picrolonic Acid [l-(4-Nitro-phenyl)-4 nitro-3-methyl-Pyrazolone-(5)]. 

Picrolonic acid (or l-p-nitrophenyl-3-methyl-4-nitro-5-pyrazolone) reagent... 

Only a few 4-nitro-2-pyrazolin-5-ones are known. They are listed in Table XXIX. The best-known of these compounds is picrolonic acid, which is 4-nitro-3-methyl-l-(4-nitrophenyl)-2-pyrazolin-5-one. This compound is widely used to form salts of basic compounds for isolation or identification. The hydrogen atom at C-4 is acidic in the 4-nitro-2-pyrazolin-5-ones because of the two adjacent electron-withdrawing groups. This hydrogen is easily replaced by metals when treated with metal alkoxides1642 and reacts with diazomethane.478... 

The alkylation of 4-nitro-2-pyrazolin-5-ones at C-4 with diazomethane478 has already been mentioned. This hydrogen atom is also replaceable with bromine.1642 Reduction of the nitro group with stannous chloride forms the corresponding amine.478,480 Picrolonic acid condenses with itself to form a bis(2-pyrazolin-5-one) connected by a double bond at the 4,4 -position, with elimination of two moles of nitrous acid.690 Condensation also occurs in the presence of phenyl-hydrazine, but 4,4 -bis[3-methyl-l-(4-nitrophenyl)-2-pyrazolin-5-one] is formed.690... 

In order to decrease the stereochemical possibilities in the final product as a result of working with racemic modifications, the acid XLIX was resolved through the quinidine salt. Both forms of the acid were obtained and a similar series of reactions was carried out using the Zei orotatory /3-methyl-5-TO-nitrobenzoylaminovaleric acid. There was thus obtained optically active l-methyl-7-ketopyrrolizidine (XXXIII) which could not consist of a mixture of more than two forms. Like the product from the racemic acid, this was an oil. When treated with hydroxylamine, however, a single, pure optically active oxime was isolated. This proved to be identical in melting point, crystalline form as observed under the microscope, and specific rotation with retronecanone oxime, and the melting points of mixtures of the two compounds showed no depression. The picrates of the aminoketoximes obtained from natural and synthetic sources were also found to be identical and showed no depression of melting-decomposition point when mixed. Likewise, the picrolonates of the oximes were identical. 

C-methyl groups. The picrate (m.p. 179-180°) and the picrolonate (m.p. 172°) have the composition of two moles of base to three moles of acid. Distillation of the alkaloid with zinc dust afforded an oily base, C12H16N2, which contained one iNT-methyl and one C-methyl group. Its formyl derivative upon reduction wdth lithium aluminum hydride formed iV,l, 7-trimethyltryptamine. When folicanthine is allowed to remain for several days in concentrated hydrochloric acid, it suffers hydrolysis to 1,7-di-methyltryptamine and a compound, C12H16O2N2, which is regarded as having structure III. On the basis of this evidence structure IV was... 

New syntheses of wopelletierine and its N-methyl derivative have been provided by Wibaut et a . " " by an extension of the process used for the preparation of di-pelletierine acetal. By the action of acetic anhydride on lithium picolyl in nitrogen, an acetyl group was inserted in the methyl group of a-picoline and the resulting -2-pyridylpropane-/S-one (a-picolyl methyl ketone), C5H4N. CHg. CO. CH3, b.p. 92°/l-5 nun., characterised as the picrate, m.p. 140-140-5°, and picrolonate, m.p. 179-5-181°, was hydrogenated in acetic acid with platinie oxide as catalyst, to dl-isopelletierine, C5H10N. CHj. CO. CH3, b.p. 62°/0-8 mm., identified as the picrate, m.p. 147-5-148-5°, and picrolonate, m.p. 177-9°. 

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