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Zicāne, Daina; Ravina, I.; Tetere, Z.; Rijkure, I.; Петрова, М. В.; Kalejs, U.

doi:10.1023/a:1020641922707

Cited by 4 publications

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“…These findings led us to study the synthesis of 1-acyl-5-amino-4-ethoxycarbonylpyrazoles from ethyl ethoxymethylenecyanoacetate (1) and monohydrazides of 2-(4-R-phenyl)-4-cyclohex-4-ene-1,1-dicarboxylic acids 2a-e described in our previous work [7]. Similar syntheses have been described in the literature.…”

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confidence: 58%

“…This reaction carried out in pyridine gives 1-acyl-5-amino-4-ethoxycarbonylpyrazoles. Pyrazole derivatives such as antipyrine, phenylbutazone, oxyphenbutazone, and sulfinpyrazole are used as nonsteroidal analgesics and antipyretics [1][2][3][4].The introduction of acyl and aracyl groups into indomethacin and ketophenylbutazone significantly enhances their therapeutic activity and lipid solubility [5,6].These findings led us to study the synthesis of 1-acyl-5-amino-4-ethoxycarbonylpyrazoles from ethyl ethoxymethylenecyanoacetate (1) and monohydrazides of 2-(4-R-phenyl)-4-cyclohex-4-ene-1,1-dicarboxylic acids 2a-e described in our previous work [7]. Similar syntheses have been described in the literature.…”

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confidence: 99%

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Synthesis of 1-Acyl-5-amino-4-ethoxycarbonylpyrazoles from Monohydrazides of Cyclohexenedicarboxylic Acids and Ethyl Ethoxymethylenecyanoacetate

Zicāne

Tetere

Ravina

et al. 2005

Chem Heterocycl Compd

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Heating monohydrazides of cyclohexenedicarboxylic acids with ethyl ethoxymethylenecyanoacetate at reflux gives the corresponding N-substituted hydrazides. This reaction carried out in pyridine gives 1-acyl-5-amino-4-ethoxycarbonylpyrazoles. Pyrazole derivatives such as antipyrine, phenylbutazone, oxyphenbutazone, and sulfinpyrazole are used as nonsteroidal analgesics and antipyretics [1][2][3][4].The introduction of acyl and aracyl groups into indomethacin and ketophenylbutazone significantly enhances their therapeutic activity and lipid solubility [5,6].These findings led us to study the synthesis of 1-acyl-5-amino-4-ethoxycarbonylpyrazoles from ethyl ethoxymethylenecyanoacetate (1) and monohydrazides of 2-(4-R-phenyl)-4-cyclohex-4-ene-1,1-dicarboxylic acids 2a-e described in our previous work [7]. Similar syntheses have been described in the literature. Despite the presence of three reaction sites in ester 1, the condensation of this compound with hydrazides occurs exclusively at the ethoxymethylene group. The prolonged heating of ethyl ester 1 with hydrazides of substituted benzoic acids in methanol at reflux in the presence of catalytic amounts of glacial acetic acid gave 5-amino-1-aroyl-4-ethoxycarbonylpyrazoles [10,11].Brief heating of ester 1 and 4(2)-methoxyhydrazides of benzoic acids at reflux gave the corresponding hydrazones, which, according to Bagrov [9], are incapable of further cyclization.We have found that both linear and cyclic products may be formed in the reaction of enol ester 1 with hydrazides of cyclohexenedicarboxylic acids 2a-e, depending on the reaction conditions. The linear intermediate can undergo cyclization. Heating enol ester 1 with hydrazides 2a-e in ethanol at reflux for 1 h gives Nsubstituted hydrazides 3a-e [12], while heating the reaction components in pyridine at reflux for 1 h leads to pyrazoles 4a-e (Scheme 1).The products, 1-acyl-5-amino-4-ethoxycarbonylpyrazoles 4a-e, are stable crystalline compounds. The reaction of pyrazoles 4a-e with formamide under conditions for the synthesis of pyrazolopyrimidines [8] leads to amides 5a-e [13], while the alkaline hydrolysis of these compounds according to Schmidt and Drye [8] gave previously unreported cyclohexenecarboxylic acids 6a-e [14] instead of the expected pyrazolecarboxylic acids.

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confidence: 58%

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confidence: 99%

Synthesis of 1-Acyl-5-amino-4-ethoxycarbonylpyrazoles from Monohydrazides of Cyclohexenedicarboxylic Acids and Ethyl Ethoxymethylenecyanoacetate

Zicāne

Tetere

Ravina

et al. 2005

Chem Heterocycl Compd

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“…Previously, 7-alkyl substituted pyridopyrimidines analogs [22] were isolated from the 2-pyridylamino-or 5-methyl-2-pyridylaminomethyleneisopropylidene malonates by also melting them.…”

Section: J Heterocyclic Chem 43 229 (2006)mentioning

confidence: 99%

New efficient approach for the synthesis of 2‐alkyl(aryl) substituted 4H‐pyrido[1,2‐a]pyrimidin‐4‐ones

Bonacorso

Righi

Rodrigues

et al. 2006

Journal of Heterocyclic Chem

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A new, efficient and easy route for the preparation of a series of 2-alkyl(aryl) substituted 4-oxo-4H-pyrido-[1,2-a]pyrimidines, where alkyl = CH 3 ; aryl = C 6 H 5 , 4-FC 6 H 4 , 4-ClC 6 H 4 , 4-BrC 6 H 4 , 4-CH 3 C 6 H 4 , 4-OCH 3 -C 6 H 4 , 4-NO 2 C 6 H 4 in 45 -80 % yield from the reaction of β-alkoxyvinyl trichloromethyl ketones with 2-aminopyridine under mild conditions, is then reported.J. Heterocyclic Chem., 43, 229 (2006).In the last years, the introduction of a trifluoro-or trichloromethyl group into an acyclic or cyclic compound have widely been studied and reviewed [1,2]. Consequently, these new organic structures can bring about remarkable changes in their physical, chemical and biological properties.Recently, we have also reported an addition/elimination sequence leading to trifluoroacetyl and trichloroacetyl acyclic enamines from the reaction of o-phenylenediamine [3], o-aminophenol [4], 1-naphthylamine [5] and S,Sdimethylsulfoximide [6] with 4-alkyl(aryl)-1,1,1-trihalo-4-alkoxyalken-2-ones. The acyclic enaminones, derived from o-phenylenediamine and o-aminophenol, were submitted to in vitro anti-tumor screens. It was observed that the trichloromethylated compounds exhibited a superior activity if compared to trifluoromethylated analog compounds. The best activity was obtained when the structure was derived from o-aminophenol and it presents a trichloroacetyl-and a p-bromophenyl substituent bound at the carbon-2 and -1, respectively [4].β-Alkoxyvinyl trichloromethyl ketones 1 proved also to be useful building blocks for the synthesis of five-, six-, and seven-, member trichloromethylated heterocycles [2] due to the fact that one of the best methods to introduce a trichloromethyl group into heterocycles is based on the trichloromethylated building block approach. This approach relies on the trichloroacetylation of enol ethers or acetals to give, in one step and good yields, the above cited ketones 1. On the other hand, the classical haloform reaction in which the trichloromethyl substituent is a leaving group is well developed [7] and systematic studies, involving the usefulness of the leaving group ability of the trichloromethyl in many synthetic transformations, were reported [2,[8][9][10][11][12][13][14]. However, just a few references from the literature report the use of the trichloromethyl substituent as a good leaving group in heterocyclic synthesis [15]. Furthermore, the synthetic strategy involving the ketones 1 and 2-aminopyridine was never applied in attempt to obtain regiospecificaly 2-alkyl(aryl)substituted 4H-pyrido[1,2-a]pyrimidin-4-ones under relative mild conditions.Although some researches, up to 1951, considered that the heterocycle obtained from the reaction of 2-aminopyridine with ethyl acetoacetate was 4-methyl-2H-pyrido[1,2-a]pyrimidin-2-one, Antaki and Petrow [16] showed (in 1951), that the product was, in fact, the 2-methyl-4-keto isomer. To prove this hypothesis, 2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one was obtained from the reaction of 2-bromopyridine with ethyl β-amin...

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“…We have used this scheme with monohydrazides of 2-arylcyclohexenyl-1,1-dicarboxylic acids 2a-e, which we had synthesized previously [5]. The hydrazides 3a-e were obtained in 60-70% yields by boiling an ethanol solution of the components.…”

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Synthesis of N′-cyclohexenecarbonyl-substituted hydrazides of 2-aminobenzoic acids and preparation of 3-cyclohexenyl-amido-1,2-dihydroquinazolin-4-ones based on them

Zicāne

Ravina

Tetere

et al. 2007

Chem Heterocycl Compd

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Cited by 4 publications

References 4 publications

Synthesis of 1-Acyl-5-amino-4-ethoxycarbonylpyrazoles from Monohydrazides of Cyclohexenedicarboxylic Acids and Ethyl Ethoxymethylenecyanoacetate

Synthesis of 1-Acyl-5-amino-4-ethoxycarbonylpyrazoles from Monohydrazides of Cyclohexenedicarboxylic Acids and Ethyl Ethoxymethylenecyanoacetate

New efficient approach for the synthesis of 2‐alkyl(aryl) substituted 4H‐pyrido[1,2‐a]pyrimidin‐4‐ones

Synthesis of N′-cyclohexenecarbonyl-substituted hydrazides of 2-aminobenzoic acids and preparation of 3-cyclohexenyl-amido-1,2-dihydroquinazolin-4-ones based on them

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