Synthesis of Important New Pyrrolo[3,4‐c]Pyrazoles and Pyrazolyl‐Pyrrolines from Heterocyclic β‐Ketonitriles

Amer, F. A.; Hammouda, M.; El-Ahl, Abdel-Aziz S.; Abdel‐Wahab, Bakr F.

doi:10.1002/jccs.200700217

Cited by 28 publications

(8 citation statements)

References 11 publications

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“…For example, in the pyrazole ring system C (4) is the most electron rich carbon, thus, H (4) in is expected to appear at higher field at δ 6.31 ppm. On the other hand, H (5) is linked to the carbon attached to nitrogen atom and thus it's deshielded to appear in the region δ 7.5 -8.5 ppm [26][27][28]. The 1 H NMR spectra of isolated reaction products revealed, in each case, a singlet signal at δ 8.5 ppm which indicates the presence of the pyrazole H (5) rather than H (4) in the structure of the isolated products.…”

Section: Resultsmentioning

confidence: 96%

Reactivity of 1-methylisoquinoline synthesis of pyrazolyl triazoloisoquinoline and thia-diazolyl isoquinoline derivatives

Hassaneen¹,

Mohammed²

2011

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The reaction of 1-methylisoquinoline 1 with hydrazonoyl halides 2 in ethanol in the presence of chitosan under microwave irradiation affords triazoloisoquinoline 4. Product 4 reacts with dimethylformamide-dimethylacetal to give enaminones 7 which react with hydrazonoyl halides to give pyrazolyl triazoloisoquinoline 13. Also, 1-methylisoquinoline 1 reacts with arylisothiocyanate to give thioanilide 15 which reacts with hydrazonoyl halides to give the corresponding thiadiazolyl isoquinoline derivatives 20, 24.

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Section: Resultsmentioning

confidence: 96%

Reactivity of 1-methylisoquinoline synthesis of pyrazolyl triazoloisoquinoline and thia-diazolyl isoquinoline derivatives

Hassaneen¹,

Mohammed²

2011

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“…The latter reaction products were assumed to be formed via initial 1,3-dipolar cycloaddition of the nitrilimines 5a-m to the activated double bond in compound 3 to afford the non-isolable cycloadducts 6a-m which undergoes loss of dimethylamine yielding the final pyrazole derivatives 7a-m. [44][45][46] The 1 H NMR spectra of the isolated products 7a-m revealed, in each case a singlet signal in the region of 8.40-8.72 ppm which indicates the presence of the pyrazole H-5 rather than H-4. This conclusion was further confirmed chemically by the reaction compounds 7a,d,g with hydrazine hydrate, to afford pyrazolo[3,4-d]pyridazines 8a-c, respectively (Scheme 2).…”

Section: Methodsmentioning

confidence: 97%

Enaminones as Building Blocks in Heterocyclic Preparations: Synthesis of Novel Pyrazoles, Pyrazolo[3,4-d]pyridazines, Pyrazolo[1,5-a]pyrimidines, Pyrido[2,3-d]pyrimidines Linked to Imidazo[2,1-b]thiazole System

Gomha¹,

Abdel‐Aziz²

2012

HETEROCYCLES

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The unreported 2-[E-3-(N,N-dimethylamino)acryloyl]-3-methyl-5,6diphenylimidazo[2,1-b]thiazole 3 was prepared via the reaction of 2-acetyl-3methyl-5,6-diphenylimidazo[2,1-b]thiazole 2 with dimethylformamide dimethyl acetal (DMF-DMA). Enaminone 3 underwent regioselective 1,3-dipolar cycloaddition with nitrilimines 5a-f, to afford the corresponding pyrazoles 7a-f.The reaction of 7a,d,g with hydrazine hydrate, afforded the pyrazolo[3,4d]pyridazines 8a-c, respectively. Enaminone 3 also reacted with a hydrazines, hydroxylamine hydrochloride, 5-aminopyrazole 11, 6-aminothiouracil 15 and hippuric acid 22. The structures of the newly synthesized compounds were confirmed by spectral data and elemental analyses.Enaminones are poly-dentate reagents that have been utilized extensively in this decade as building blocks in organic synthesis. 1-9 Furthermore, many enaminones were found to exhibit several biological activities as antitumor, antibacterial and anticonvulsant agents. 10,11 On the other hand, imidazoles possess important biological, pharmacological and therapeutic activities, 12,13 where midazoles are present in compounds that have antiasthmatic, 16 anti-inflammatory, 17 antiulcerative, 18 antithrombotic, 19 fungicidal 20 and herbicidal activities. 21 Furthermore, some imidazo[2,1b]thiazoles were active against various cancer cell lines. 22 Much interest has also been focused on the chemistry and anticonvulsant, analgesic, 23 antibacterial 24 and antisecretory 25 activities displayed by HETEROCYCLES, Vol. 85, No. 9, 2012 2291 1 2 3 Scheme 1Treatment of the enaminone 3 with nitrilimines 5a-m, [liberated in situ from the corresponding hydrazonyl halides 4a-m, respectively, with triethylamine in refluxing toluene], it afforded the 3,4disubstituted-1H-pyrazoles 7a-m, respectively (Schemes 2). The latter reaction products were assumed to be formed via initial 1,3-dipolar cycloaddition of the nitrilimines 5a-m to the activated double bond in compound 3 to afford the non-isolable cycloadducts 6a-m which undergoes loss of dimethylamine yielding the final pyrazole derivatives 7a-m. [44][45][46] The 1 H NMR spectra of the isolated products 7a-m revealed, in each case a singlet signal in the region of 8.40-8.72 ppm which indicates the presence of the pyrazole H-5 rather than H-4. This conclusion was further confirmed chemically by the reaction compounds 7a,d,g with hydrazine hydrate, to afford pyrazolo[3,4-d]pyridazines 8a-c, respectively (Scheme 2).

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“…17 Moreover various sulfur compounds have been found to have other biological properties. [22][23][24][25] In view of these reports and in continuation with our previous work in the synthesis of biologically active heterocycles, [26][27][28][29][30] in this article we detail our synthesis of some new heterocycles with 1-phenyl-5-(thiophen-2-yl)-pyrazole moiety.…”

Section: Introductionmentioning

confidence: 87%

Synthesis and Characterization of Some New Heterocycles Incorporating the 1-Phenyl-5-(2-thienyl)pyrazole Moiety

Abdel‐Wahab

El-Ahl

2010

Phosphorus, Sulfur, and Silicon and the Related Elements

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1-Phenyl-3-(2-thienyl)-1H-pyrazole-5-carbohydrazide 4 was prepared from 2-acetylthiophene by reaction with diethyl oxalate and phenylhydrazine followed by hydrazine hydrate. The reaction of the hydrazide 4 with phthalic anhydride, aromatic aldehydes, and alkene derivatives gave imide 5, hydrazones 6a-d, and bis-pyrazoles 7 and 8, respectively, while its reaction with phenyl isothiocyanate led to thiosemicarbazide 9. The reaction of the latter with ethyl bromoacetate and phenacylbromide afforded 4-thiazolidinone 10 and 1,3-thiazole 11 derivatives, respectively. Reaction of 4 with carbon disulfide in the presence of potassium hydroxide gave potassium hydrazinecarbodithioate derivative 12, which was used as a starting material in the preparation of 2-thioxothiazol-3(2H)-yl)-5-(2-thienyl)-1H-pyrazole-3-carboxamide 14; 1,3,4-thiadiazol-2(3H)-ylidene)-1-phenyl-5-(2-thienyl)-1H-pyrazole-3-carbohydrazides 16a-c; 4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)pyrazole derivative 13; Schiff bases 17a,b; and 1,2,4-triazolo[3,4-b][1,3,4]thiadiazine derivatives 18 and 19a-e.

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Synthesis of Important New Pyrrolo[3,4‐c]Pyrazoles and Pyrazolyl‐Pyrrolines from Heterocyclic β‐Ketonitriles

Cited by 28 publications

References 11 publications

Reactivity of 1-methylisoquinoline synthesis of pyrazolyl triazoloisoquinoline and thia-diazolyl isoquinoline derivatives

Reactivity of 1-methylisoquinoline synthesis of pyrazolyl triazoloisoquinoline and thia-diazolyl isoquinoline derivatives

Enaminones as Building Blocks in Heterocyclic Preparations: Synthesis of Novel Pyrazoles, Pyrazolo[3,4-d]pyridazines, Pyrazolo[1,5-a]pyrimidines, Pyrido[2,3-d]pyrimidines Linked to Imidazo[2,1-b]thiazole System

Synthesis and Characterization of Some New Heterocycles Incorporating the 1-Phenyl-5-(2-thienyl)pyrazole Moiety

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