acid, pivaloylpyrotartaric acid, reactions with acylhydrazines.It is known that (het)aroylpyrotartaric acids, their esters and amides react with hydrazines to give derivatives of 5-(het)aryl-1H-pyrazol-3-carboxylic acid [1,2]. As the result of the reaction of pivaloylpyrotartaric acid 1 (2-hydroxy-5,5-dimethyl-4-oxo-2-hexenoic acid) the hydrazides of aromatic carboxylic acids under mild conditions we have obtained 2-aroylhydrazono-5,5-dimethyl-4-oxohexanoic acids (2a,b, hydrazone form A) in preparative yields, together with in solution the minor pyrazoline tautomer -1-aroyl-5-tert-butyl-5-hydroxy-4,5dihydro-1H-pyrazol-3-carboxylic acids (form B). The structures of the latter are in excellent agreement with those of 5-aryl-5-hydroxy-2-pyrazolin-3-carboxamides obtained previously [3].
Keywords: acetophenone, dibenzoylmethane, diethyl oxalate, ethyl acetate, ethyl esters of 2-hydroxy-3-oxo-2,3-dihydrofuran-2-ylacetic acids.2-Hydroxy-2,3-dihydrofuran-3-ones are successfully used in organic synthesis, especially for the preparation of biologically active compounds [1][2][3][4][5]. The known methods for the synthesis of 5-aryl-2-hydroxyfuran-3(2H)-ones generally include several stages and are not suitable for preparation [4,5]. We have developed a very simple and suitable one-step method for the synthesis of 2-hydroxy-3-oxo-2,3-dihydrofuran-2-ylacetate esters 1,2 by the reaction of ethyl acetate with diethyl oxalate and methyl ketones (for example, acetophenone or dibenzoylmethane) in the presence of sodium hydride with subsequent treatment of the mixture with hydrochloric acid: Me O EtO O O EtO OEt O R O H O O R O OEt 1) NaH 2) HCl -EtOH 1, 2 + + 1 R = H, 2 R = PhCOApart from compound 1, a secondary product -Z-2-hydroxy-4-oxo-4-phenyl-2-butenoic acid (benzoyltartaric acid) was isolated in 27% yield from the reaction mixture of ethyl acetate, diethyl oxalate, and acetophenone, which was identified by comparison with a known sample [6].
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Keywords: 3-hydroxy-3-(2-oxoethyl)-2,3-dihydropyridazin-4(1H)-ones, 2-(2-oxoethylidene)furan-3-(2H)-ones, reactions with benzoic and p-nitrobenzoic isopropylidenehydrazides.The reactions of 2-ylidenefuran-3(2H)-ones with hydrazine or arylhydrazines lead to the formation of hydrazino derivatives of 3-oxofuran [1], 3-acylpyrazoles [2-4], or 3-alkyl(ylidene)-substituted pyridazine-4(1H)-ones [4]. It is known that the action of aroylhydrazines on 3-oxofuran-2(3H)-ylideneacetates leads to the formation of 1-aroylamino-2-hydroxy-3-oxo-2,3-dihydro-1H-pyrrol-2-ylacetic esters [5]. Other reactions of acyl or ylidene derivatives of hydrazine with five-membered 2-ylidene-2,3-dihydro-3-oxo heterocycles had not been studied before our investigations.As a result of the reaction of methyl 3-oxo-5-phenylfuran-2(3H)-ylideneacetate (1a) or 2-[2-(4-chlorophenyl)-2-oxoethylidene]-5-phenylfuran-3(2H)-one (1b) with benzoic or p-nitrobenzoic isopropylidenehydrazides we unexpectedly obtained preparative yields of the previously unknown stable cyclic O,N-acetals -3-hydroxy-3-(2-oxoethyl)-6-phenyl-2,3-dihydropyridazin-4(1H)-ones 2a-d. Equilibrium tautomeric forms C (5) H (A) and C (5) H 2 (B) were detected in solutions of compounds 2c,d in DMSO-d 6 .When the isopropylidenehydrazides of carboxylic acids are brought into reaction with 2-(2-oxoethylidene)furan-3(2H)-ones 1 nucleophilic attack by the NH group of the equilibrium enamino form NH-CMe=CH 2 of the reagent probably occurs at the C (5) atom of the ring in the substrate 1 with subsequent intramolecular heterocyclization of the enehydrazinocarbonyl intermediate, hydrolytic elimination of a molecule of acetone, and the formation of 3-hydroxy-3-(2-oxoethyl)-6-phenyl-2,3-dihydropyridazin-4(1H)-ones 2. The regioselectivity of NH-nucleophilic attack by the hydrazides at the electron-deficient center C (5) of compounds 1 during the theoretically possible attack also at the C (2) , C (2') , or C (3) atoms confirms the probable orbital control of the reaction [6]. __________________________________________________________________________________________
In solution, the acylhydrazines (III) form a pyrazoline tautomer. -(KOZMINYKH, V. O.; GONCHAROV, V. I.; KOZMINYKH, E. N.; OBORIN, D. B.; Chem. Heterocycl. Compd. (N. Y.) 42 (2006) 5, 698-700; Perm' State Pedagog. Univ., Perm' 614990, Russia; Eng.) -C. Oppel
KOZMINYKH, E. N.; GONCHAROV, V. I.; OBORIN, D. B.; KOZMINYKH, V. O.; Chem. Heterocycl. Compd. (N. Y.) 43 (2007) 5, 658-659; Moscow State Univ. Technol. Manage., Perm' 614065, Russia; Eng.) -C. Cyrus 05-096
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