A mild and efficient method for halogenation of 3,5-dimethyl pyrazoles by ultrasound irradiation using N-halosuccinimides

Stefani, Hélio A.; Pereira, Cláudio M. P.; Almeida, Roberta B.; Braga, Rodolpho C.; Guzen, Karla P.; Cella, Rodrigo

doi:10.1016/j.tetlet.2005.08.027

Cited by 79 publications

(25 citation statements)

References 22 publications

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“…32 Finally, although the reaction conditions could be used for side chain bromination reaction of methyl aromatics, such as pyridines and benzoderivatives, 33 in the case of methyl pyrazoles there are no reports in the literature about side chain bromination reactions. 23 Our results of the bromination reaction are in accordance with those described in the literature.…”

Section: Resultssupporting

confidence: 92%

“…Additionally, halogenation of pyrazolo [1,5-a]pyrimidines can be used to obtain key substructures in a large variety of compounds with important biological activities, and the halogenated compounds also can be used as reagents in cross-coupling reactions with terminal acetylenes, organotin aryl derivatives or aryl boronic acids. 23 Thus, in the course of our investigations on heterocyclic chemistry and in view of the growing importance of halogenated heterocycles, the aim of this study is to show: (i) the synthesis of halomethyl-containing pyrazolo [1,5-a] pyrimidines (3) from the reaction of 3-amino-5-methyl-1H-pyrazole with 4-alkoxy-1,1,1-trichloro-3-alken-2-ones (1) or β-dimethylaminovinyl ketones (2) (Scheme 1) and (ii) the bromination of the pyrazolo [1,5-a]pyrimidines (3) with bromine to obtain 3-bromopyrazolo[1,5-a]pyrimidines (4) (Scheme 2).…”

Section: Introductionmentioning

confidence: 99%

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2-methyl-7-substituted pyrazolo[1,5-a]pyrimidines: highly regioselective synthesis and bromination

Martins¹,

Scapin²,

Frizzo³

et al. 2009

J. Braz. Chem. Soc.

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Este trabalho descreve a reação de ciclocondensação de 3-amino-5-metil-1H-pirazol com 1,1,1-tricloro-4-alcóxi-3-alquen-2-onas [CCl 3 C(O)CH=C(R 1 )OR, onde R 1 /R = H/Me, Me/Et, Et/Me, Pr/Et, Bu/Me, iso-Bu/Me] e β-dimetilaminovinil cetonas [R 2 C(O)CH=CHNMe 2 , onde R 2 = Ph, Ph-4-Me, Ph-4-F, Ph-4-Cl, Ph-4-Br, Ph-4-NO 2 , fur-2-il, tien-2-il, pirrol-2-il, pyrid-2-il], em refluxo de ácido acético para a obtenção de uma série de catorze pirazolo [1,5-a]pirimidinas. Os produtos foram obtidos em bons rendimentos (65-98%). Este trabalho apresenta ainda uma metodologia simples e seletiva para a obtenção de 3-bromo-pirazolo [1,5-a] IntroductionAmong the broad range of templates, heterocycle scaffolds represent the most promising molecules as lead structures in the discovery of novel synthetic drugs 1 and the revision of synthetic methods for their obtainment are intense.2 In particular, the pyrazolo[1,5-a]pyrimidine heterocyclic can be found in a large number of pharmaceutical agents with a diverse range of activities. Pyrazolo [1,5-a] 13 However, a facile procedure that can incorporate diversity structural it is high desirable. There are a limitedness number and variety of pyrazolo pyrimidines trifluoromethyl substituted described in literature.14 Conversely, pyrazolo[1,5-a] pyrimidines trichloromethyl substituted are rare. 15 The most convenient method to construct trihalogenated compounds is to use halogen-containing building blocks as starting reagents. 16,17 Our research group developed a general procedure for preparing β-alkoxyvinyl trihalomethyl ketones by acylation of enol ethers and acetals using 2-Methyl-7-Substituted Pyrazolo[1,5-a]pyrimidines J. Braz. Chem. Soc. 206 functionalized acyl groups CX 3 CO (where X = F and Cl). 16In addition, we have exhaustively studied the versatility of the β-alkoxyvinyl trihalomethyl ketones on heterocyclic synthesis and our research have resulting in outstanding contributions to heterocyclic synthesis. 2,16 On the other hand, aminopyrazoles are known to be highly reactive heterocyclic compounds, e.g., the nucleophilic attack of C-4 of the aminopyrazoles on the carbonyl groups, 18 and the N-nucleophilic attack on aromatic aldehydes yielding aldimines, have been extensively reported.19 Aminopyrazoles also react as electron-rich dienophiles in the inverse electron demand Diels-Alder [4+2] cycloaddition reactions. 20The use of 3-and 5-aminopyrazoles as precursors of fused heterocycles, such as pyrazolo[1,5-a]pyrimidines 21 and pyrazolo [3,4-b]pyridines 22 has also been described. Additionally, halogenation of pyrazolo[1,5-a]pyrimidines can be used to obtain key substructures in a large variety of compounds with important biological activities, and the halogenated compounds also can be used as reagents in cross-coupling reactions with terminal acetylenes, organotin aryl derivatives or aryl boronic acids. 23 Thus, in the course of our investigations on heterocyclic chemistry and in view of the growing importance of halogenated heterocycles, the aim of this study is to show...

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

2-methyl-7-substituted pyrazolo[1,5-a]pyrimidines: highly regioselective synthesis and bromination

Martins¹,

Scapin²,

Frizzo³

et al. 2009

J. Braz. Chem. Soc.

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“…To a solution of corresponding nitro derivative 11a-11c (1 mmol) in 20 cm 3 of methanol (10 V) was added 10% Pd/C (10% loading) under nitrogen atmosphere. The reaction mixture was charged to a Parr shaker apparatus and evacuated and filled with hydrogen gas three times at room temperature and then hydrogenated at 3 kg/cm 2 for 2 h. Completion of the reaction was monitored by TLC.…”

Section: -Nitro-n-(4-trifluoromethyl-benzyl)-benzamide (11a)mentioning

confidence: 99%

“…Natural products containing pyrazole nucleus are very scarce, but many synthetic pyrazoles are known to be biologically active [3]. Examples of leading drugs containing pyrazole rings are celebrex [4], sildenafil (Viagra) [5], zaleplon [6], and fipronil [7].…”

Section: Introductionmentioning

confidence: 99%

Design, Synthesis, and Evaluation of the Anticancer Properties of a Novel Series of α‐(Benzoylamino)‐β‐substituted Acrylic Amide Derivatives of Pyrazolo[1,5‐a]pyrimidine

Sasikumar

Mohanasrinivasan

Kumar

et al. 2017

Journal of Heterocyclic Chem

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A novel series of α‐(benzoylamino)‐β‐substituted acrylic amide derivatives of pyrazolo[1,5‐a]pyrimidine has been synthesized using a convergent multistep synthesis. The synthesized compounds were characterized by 1H NMR, 13C NMR, ESI‐MS, and IR analyses. Those new compounds were screened for their in vitro antiproliferative activity using an MTT assay analysis. Out of nine derivatives synthesized in the current study, compounds 13g, 13d, 13h, and 13i exhibited the greatest anticancer activities in HeLa and HepG2 cell lines. The in vitro anticancer activity of compound 13g against HeLa, HepG2, and MCF‐7 cell lines is superior to the marketed drugs paclitaxel and SAHA.

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“…Examples of natural products containing a pyrazole nucleus are very scarce, but many synthetic pyrazoles are biologically active, 1 and some have shown pharmacological utility as antipyretic, analgesic, and antiinflammatory agents, 1−3 as well as for their antimicrobial properties, especially antibacterial 4 and antifungal activities. 5 Moreover, this heterocyclic moiety is present within the core structure of numerous drugs, including Celebrex, Viagra, and Zaleplon.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of new pyrazole and antibacterial pyrazolopyrimidine derivatives

Rahmouni¹,

Romdhane²,

Said³

et al. 2014

Turk J Chem

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3-Substituted-1-phenyl-1 H -pyrazolo[3,4-d ]pyrimidin-4-amines 2a-c were synthesized by treating 5-aminopyrazole-4-carbonitriles 1a-c with formamide. The reactivity of compounds 1a-c towards some cyclic anhydrides was studied. The condensation of 5-aminopyrazole-4-carbonitrile 1b with triethylorthoformate gives imidate 7b, which reacts with a series of primary amines and leads to pyrazolo[3,4-d ]pyrimidine-4-amines 9 and 10. The reaction of imidate 7b with ammonia and hydroxylamine afforded pyrazolopyrimidine 2b and pyrazolo[3,4-d ]pyrimidin-5-(4 H) -ol 11, respectively. The synthesized compounds were completely characterized by 1 H NMR, 13 C NMR, IR, and HRMS.The antibacterial activity of some new synthesized compounds was evaluated and appeared to be significant.

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A mild and efficient method for halogenation of 3,5-dimethyl pyrazoles by ultrasound irradiation using N-halosuccinimides

Cited by 79 publications

References 22 publications

2-methyl-7-substituted pyrazolo[1,5-a]pyrimidines: highly regioselective synthesis and bromination

2-methyl-7-substituted pyrazolo[1,5-a]pyrimidines: highly regioselective synthesis and bromination

Design, Synthesis, and Evaluation of the Anticancer Properties of a Novel Series of α‐(Benzoylamino)‐β‐substituted Acrylic Amide Derivatives of Pyrazolo[1,5‐a]pyrimidine

Synthesis of new pyrazole and antibacterial pyrazolopyrimidine derivatives

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