Synthetic Routes to Pyrazole‐3(5)‐carboxylates

Khidre, Rizk E.; Abdel‐Wahab, Bakr F.; Farahat, Abdelbasset A.; Mohamed, Hanan A.

doi:10.1002/jhet.1504

Cited by 16 publications

(5 citation statements)

References 103 publications

(90 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The pyrazole motif is an attractive building block for the pharmaceutical as well as for the agrochemical industry, since those derivatives display a broad spectrum of biological activities . Of particular importance are pyrazole carboxylates; e.g., ethyl 5-propyl-1 H -pyrazole-3-carboxylate is a key intermediate for the synthesis of sildenafil (Viagra) . Pyrazoles are usually prepared either by condensation of a hydrazine derivative and a 1,3-dicarbonyl compound or by 1,3-dipolar cycloaddition of diazo compounds and alkynes, which provides a direct access to substituted pyrazoles .…”

Section: Resultsmentioning

confidence: 99%

Laboratory-Scale Membrane Reactor for the Generation of Anhydrous Diazomethane

et al. 2016

View full text Add to dashboard Cite

A configurationally simple and robust semibatch apparatus for the in situ on-demand generation of anhydrous solutions of diazomethane (CH2N2) avoiding distillation methods is presented. Diazomethane is produced by base-mediated decomposition of commercially available Diazald within a semipermeable Teflon AF-2400 tubing and subsequently selectively separated from the tubing into a solvent- and substrate-filled flask (tube-in-flask reactor). Reactions with CH2N2 can therefore be performed directly in the flask without dangerous and labor-intensive purification operations or exposure of the operator to CH2N2. The reactor has been employed for the methylation of carboxylic acids, the synthesis of α-chloro ketones and pyrazoles, and palladium-catalyzed cyclopropanation reactions on laboratory scale. The implementation of in-line FTIR technology allowed monitoring of the CH2N2 generation and its consumption. In addition, larger scales (1.8 g diazomethane per hour) could be obtained via parallelization (numbering up) by simply wrapping several membrane tubings into the flask.

show abstract

Section: Resultsmentioning

confidence: 99%

Laboratory-Scale Membrane Reactor for the Generation of Anhydrous Diazomethane

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Pyrazole-3-carboylates can be synthesized using various efficient procedures (e.g. Khidre et al, 2016;Radwan et al, 2014). As part of our studies in this area, we now describe the synthesis and structure of the title compound.…”

Section: Structure Descriptionmentioning

confidence: 99%

Ethyl 1-phenyl-1,4-dihydroindeno[1,2-c]pyrazole-3-carboxylate

et al. 2018

Self Cite

View full text Add to dashboard Cite

The non-H atoms of the title molecule, C 19 H 16 N 2 O 2 , are almost coplanar (r.m.s. deviation = 0.019 Å ), apart from the phenyl group, which is disordered with two components of almost equal occupancy: the dihedral angle between them is 78.9 (3) . In the crystal, weak C-HÁ Á ÁN hydrogen bonds link the molecules into [001] chains and aromatic -stacking interactions [shortest centroid-centroid separation = 3.747 (2) Å ] form columns parallel to the c-axis direction. Structure descriptionPyrazole-3-carboylates can be synthesized using various efficient procedures (e.g. Khidre et al., 2016;Radwan et al., 2014). As part of our studies in this area, we now describe the synthesis and structure of the title compound.The title molecule is almost planar (r.m.s. deviation = 0.017 Å ) apart from the phenyl ring (Fig. 1), which is disordered with two components of almost equal occupancy [50.5 (4)% and 49.5 (4)%]. The components of the disordered phenyl rings are twisted by 54.6 (2) and 46.9 (2) away from the least-squares plane of the rest of the molecule and the angle between the disorder components is 78.9 (3) .In the crystal, weak C-HÁ Á ÁN hydrogen bonds (Table 1) link the molecules into [001] chains and aromatic -stacking interactions [shortest centroid-centroid separation = 3.747 (2) Å ] generate columns parallel to the c-axis direction (Fig. 2).

show abstract

“…8 The synthesis of this bicyclic scaffold are scarcely found in the literature and are almost exclusively based on an existing pyrazole motif. [9][10][11] The desired bicyclic framework is aerward obtained either according to a mononuclear heterocyclic rearrangement 1,8 (known as Boulton-Katritzky rearrangement -Route A), an annulation strategy (Route B) [12][13][14][15][16][17] or other miscellaneous methods (using isothiocyanates, 18 nitrilimines, 9 arylsemicarbazides 19 or 2-cyano-N-methyl-acrylamide 20 ).…”

Section: Introductionmentioning

confidence: 99%