Study of the interaction of 2H-furo[3,2-b]pyran-2-ones with nitrogen-containing nucleophiles

• Constantine V. Milyutin,
• Andrey N. Komogortsev and
• Boris V. Lichitsky

Beilstein J. Org. Chem. 2025, 21, 556–563, doi:10.3762/bjoc.21.44

• communication we investigated the interaction of substituted 2H-furo[3,2-b]pyran-2-ones 1 with nitrogen-containing nucleophiles (Scheme 1b, this work). As a result, the general approach to preparation of pyrazolones with a 3-hydroxy-4-pyranone unit was developed. It’s important to underline that both pyrazolone

• . So, reflux of the mixture of starting materials in AcOH for 24 h led to pyrazolone 8a in 37% yield (Table 1, entry 1). Note that increasing the process time didn’t affect on the observed result (Table 1, entry 2). Next, we tested the studied reaction applying various solvents and in all cases the

• elaborated above for the preparation of enamines 4. Interaction of starting compound 1a with hydrazine was performed using acetic acid as a solvent at reflux for 8 h. As a result, the appropriate pyrazolone 10a, unsubstituted at both nitrogen atoms, was obtained with 73% yield (Scheme 5b). Based on the

Recent advances in organocatalytic atroposelective reactions

• Henrich Szabados and
• Radovan Šebesta

Beilstein J. Org. Chem. 2025, 21, 55–121, doi:10.3762/bjoc.21.6

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• the corresponding pyrazolone derivatives, thereby providing access to both bis(pyrazolyl) and bis(pyrazolonyl)methanes. Enaminones 81 can be generated as intermediates by condensation of 1,3-dicarbonyl compounds and DMF-dimethylacetal (DMFDMA, 79). The reaction is catalyzed by the solvent 2,2,2

• that ninhydrin (150), as an electrophile, reacts with the enol tautomeric form 153 of pyrazolone 152 to give ninhydrin-substituted pyrazoles 151 in a three-component reaction, as depicted in Scheme 52 [158]. The two-component formation of pyrazolone 156 from acetylenedicarboxylates and phenylhydrazine

Primary amine-catalyzed enantioselective 1,4-Michael addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones

• Pooja Goyal,
• Akhil K. Dubey,
• Raghunath Chowdhury and
• Amey Wadawale

Beilstein J. Org. Chem. 2024, 20, 1518–1526, doi:10.3762/bjoc.20.136

• organocatalyzed asymmetric Michael addition reaction of 4-monosubstituted pyrazol-5-ones to simple enones for the synthesis of pyrazolone derivatives [25]. Despite these progresses, arylidene/heteroarylideneacetones have remained untapped by 4-unsubstituted pyrazolin-5-ones under asymmetric organocatalytic or

• enantioselectivities (84.5–95% ee). In addition, pyrazolone 2g with a substituent in the meta-position of the N-aryl group also participated in the reaction and the desired product 3cg was isolated in 87% yield and 95% ee. Notably, a phenyl substituent at the C3 position of pyrazolone 2h was found to be compatible

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• pyrazolone derivatives with N-thiophthalimides catalyzed by 1 mol % of chiral iminophosphorane organocatalyst was carried out under mild conditions [103]. Solvent control in the procedure can affect the yield of products due to the solubility of the catalysts. Various solvents, such as acetone, ethyl acetate

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• achieved through an asymmetric aza-Friedel–Crafts reaction. As substrate the authors chose the racemate of indole moiety 99 bearing a 5-acetyloxypyrazol substitution at the C3 position which was coupled with the pyrazolone-derived imine 100 to functionalize the C2–H bond of the indole ring. This aromatic

• electrophilic substitution also gave a quaternary aza-stereocenter in the pyrazolone moiety. Axial chirality associated with central chirality in the product structures was influenced by chiral phosphoric acid catalyst P23. To freeze the C–C bond rotation, the pyrazole moiety in 99 required sterically demanding

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• [69]. Herein, Li and co-workers developed a new asymmetric synthesis of atropisomeric pyrazole derivatives 56 via an enantioselective reaction of azonaphthalene 54 with pyrazolone 55 using 5 mol % chiral phosphoric acid CPA 16. Substrates bearing electron-donating and electron-withdrawing groups gave

• pyrazolone-enol intermediates to the N–N double bonds of azonaphthalenes [70]. On the other hand, N-arylcarbazole frameworks are also abundant in pharmaceuticals, agrochemicals, natural products, and functional OLED materials [71][72]. Therefore, the construction of axially chiral N-arylcarbazoles is

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• -Michael addition of 2-tosylaminoenones with unsaturated pyrazolones using squaramide as catalyst. The reaction proceeded smoothly under mild conditions to afford the corresponding spiro[pyrazolone-tetrahydroquinolines] in high yields (up to 99%) with excellent diastereoselectivities (up to >25:1 dr) and

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• intermediate and the coumarin through hydrogen bonding, as shown in Scheme 25. An enantioselective one-pot synthesis of spiro[dihydrofurocoumarin/pyrazolone] 83 mediated by quinine and squaramide catalyst 84 was reported by Xu et al. [61]. The work draws attention for the wide range of compounds obtained with

• [dihydrofurocoumarin/pyrazolone] 83. Michael/hemiketalization addition enantioselective of hydroxycoumarins (1) to: (a) enones 2 and (b) α-ketoesters 86. Synthesis of 2,3-dihydrofurocoumarins 89 through Michael addition of 4-hydroxycoumarins 1 to β-nitrostyrenes 88. Synthesis of pyrano[3,2-c]chromene derivatives 93

Organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones

• Chandrakanta Parida and
• Subhas Chandra Pan

Beilstein J. Org. Chem. 2021, 17, 1447–1452, doi:10.3762/bjoc.17.100

• available bifunctional thiourea catalyst was employed in the methodology. Reactions of α-nitroketones with unsaturated pyrazolone and with 4-benzylidenepyrrolidine-2,3-dione. Reaction of 4-benzylidenedihydrofuran-2,3-dione (4) with α-nitroketones 2b,c. Reaction conditions: furan 4 (0.1 mmol), α-nitroketone

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• compounds as binucleophiles for the construction of various carbocycles, heterocycles as well as in asymmetric catalysis [44][45][46][47][48][49][50]. Our initial objective to trap the aza vinyl rhodium carbenoid using 1,3-dicarbonyl compounds to form pyrazolone was unsuccessful which instead led to the

Microwave-assisted synthesis of biologically relevant steroidal 17-exo-pyrazol-5'-ones from a norpregnene precursor by a side-chain elongation/heterocyclization sequence

• Gergő Mótyán,
• László Mérai,
• Márton Attila Kiss,
• Zsuzsanna Schelz,
• Izabella Sinka,
• István Zupkó and
• Éva Frank

Beilstein J. Org. Chem. 2018, 14, 2589–2596, doi:10.3762/bjoc.14.236

• action of these derivatives. Amongst steroidal 17-exo-heterocycles, those containing a pyrazole heteroaromatic ring are of special relevance with respect to the above-mentioned bioactivities [6][7][8][9]. Interestingly, so far only a few examples of compounds in which a pyrazolone moiety is attached to

• spectroscopy supplemented by IR and MS measurements. The dependence of the tautomeric equilibrium on the polarity of the applied solvent was observed during the NMR experiments. For example, in the 1H NMR spectrum of compound 7f recorded immediately after dissolution in CDCl3, the pyrazolone heterocyclic ring

• . This indicates that the pyrazolone heterocyclic ring at the 17β position is a promising scaffold for the design of anticancer agents of the Δ5 androstene series. 1H NMR spectra of compound 7f in CDCl3 (top; # solvent signal) and in DMSO-d6 (bottom; # solvent signal). Multistep synthesis of steroidal β

Two new 2-alkylquinolones, inhibitory to the fish skin ulcer pathogen Tenacibaculum maritimum, produced by a rhizobacterium of the genus Burkholderia sp.

• Dandan Li,
• Naoya Oku,
• Atsumi Hasada,
• Masafumi Shimizu and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2018, 14, 1446–1451, doi:10.3762/bjoc.14.122

• Burkholderia produce many more secondary metabolites than reported, as this group was previously classified into the genus Pseudomonas [8]. In fact, the high capacity of Burkholderia in secondary metabolism is demonstrated by the presence of unique functionalities, such as monocyclic 3-pyrazolone [9], α

An unusual thionyl chloride-promoted C−C bond formation to obtain 4,4'-bipyrazolones

• Gernot A. Eller,
• Gytė Vilkauskaitė,
• Algirdas Šačkus,
• Vytas Martynaitis,
• Ashenafi Damtew Mamuye,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2018, 14, 1287–1292, doi:10.3762/bjoc.14.110

• racemic mixture or the meso-form came into consideration. The single crystal X-ray analysis disclosed that the molecule of the newly obtained compound 3a consists of two pyrazolone residues, which are directly connected to each other by a single covalent carbon–carbon bond between the asymmetric sp3

• latter carbon atom. In contrast, only very few examples are described for pyrazolones with a C=O substructure attached to pyrazole C4. Thus, 3-methyl-1-phenyl-4-toluoyl-5-pyrazolone (= (5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)(4-methylphenyl)methanone) upon treatment with oxovanadium(V) compounds

• two pyrazolone units is 1.544(3) Å. For details see the Supporting Information File 1. Arrangement (4R,4'R)- and (4S,4'S)-3a enantiomers in the crystal unit drawn with 50% displacement ellipsoids. The hydrogen bonds are shown by dashed lines. Supplementary crystallographic data for compound 3a can be

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• aldehydes, benzoyl chloride and ethyl acetoacetate to append hydrazone, carbohydrazide and pyrazolone type moieties on pyrazolo[3,4-d]pyrimidine. Further, hydrazinyl derivative 189 provided various fused triazolylpyrazolo[3,4-d]pyrimidines on treatment with various reagents like aliphatic acids, benzoyl

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• ethyl acetate at room temperature, led to a mixture of pyrazolone 87 and pyridazine 88 in favor of the former compound (54%) [71] (Scheme 27). Heating equimolar amounts of E-1a and dimedone (89) in ethanol at reflux for 8 h afforded 4H-pyran 90 as the heterocyclization product of the initially formed

One-pot multistep mechanochemical synthesis of fluorinated pyrazolones

• Joseph L. Howard,
• William Nicholson,
• Yerbol Sagatov and
• Duncan L. Browne

Beilstein J. Org. Chem. 2017, 13, 1950–1956, doi:10.3762/bjoc.13.189

• designed a 2-step reaction related to our recent work on liquid assisted grinding effects of the fluorination of 1,3-dicarbonyl compounds, in which the dicarbonyl will initially form a pyrazolone in the first reaction prior to undergoing difluorination in the second step (Scheme 1) [17]. Notably this

• approach will likely require a grinding auxiliary in the first step where two liquid phases react and will be catalysed by an acid to afford a solid pyrazolone material. This will then be followed by a difluorination reaction between solid–solid reactants, this reaction may perform better in the presence

• pyrazolone formation was investigated as the first step of the two step process, we opted to keep the ball size, ball number, jar size and jar and ball material as in our previous studies to reduce the number of variables for this analysis [17]. In the first instance, simply milling the two liquids in the

A novel 4-aminoantipyrine-Pd(II) complex catalyzes Suzuki–Miyaura cross-coupling reactions of aryl halides

• Claudia A. Contreras-Celedón,
• Darío Mendoza-Rayo,
• José A. Rincón-Medina and
• Luis Chacón-García

Beilstein J. Org. Chem. 2014, 10, 2821–2826, doi:10.3762/bjoc.10.299

• -free catalysts for SM coupling reactions. Transition metal complexes that have shown a wide range of biological activity are those containing the pyrazolone derivative 4-aminoantipyrine (4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one, or simply “4-AAP”) [18]. Pyrazoles, in general, are one of the

One-pot four-component reaction for convenient synthesis of functionalized 1-benzamidospiro[indoline-3,4'-pyridines]

• Chao Wang,
• Yan-Hong Jiang and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2014, 10, 2671–2676, doi:10.3762/bjoc.10.281

• acetylenedicarboxylate to give the pyrazolone intermediate in the previously reported multicomponent reactions containing hydrazine and acetylenedicarboxylate [25][26][27]. Here, due to the protection of the benzoyl group, only the free amino group in benzohydrazide took part in the reaction to give the 1'-benzamido

• tautomerization results in the final spiro compound 1. In this process, the initially formed zwitterrionic intermediate (A) does not cyclize to give pyrazolone intermediate as in the reaction of hydrazine with acetylenedicarboxylate. Thus, benzohydrazide shows very different reactivity to that of hydrazine in the

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• pyrazolones The group of Krasavin prepared both pyrazole- as well as pyrazolone-containing peptidomimetics via a sequential hydrazino-Ugi/Paal–Knorr condensation [94]. In their first approach, pyrazoles were obtained in good yields, however, with a limited scope of the condensation substrates (Scheme 32

An easy direct arylation of 5-pyrazolones

• Hao Gong,
• Yiwen Yang,
• Zechao Wang and
• Chunxiang Kuang

Beilstein J. Org. Chem. 2013, 9, 2033–2039, doi:10.3762/bjoc.9.240

• ; C–H bond activation; Pd(OAc)2; pyrazolone; Introduction 5-Pyrazolones are attracting considerable research interest because of their unique chemical properties and their structures that facilitate their application as biological and pharmaceutical intermediates and products [1][2][3]. Over the

• , cyclooxygenase isoenzymes, platelet tromboxane synthesis, and prostanoid synthesis in humans [12][13]. Recently, pharmacologists have developed a novel class-II c-met inhibitor, whose structural unit is a pyrazolone ring [14]. The great medicinal significance and broad applications of pyrazolones prompted us to

• synthesize a new series of heterocyclic compounds containing the pyrazolone moiety. The reaction of pyrazolones with arylboronic acids is an attractive approach for the synthesis of arylpyrazolone [15][16]. However, it often needs pre-formation of halo-pyrazolones. Transition metal-catalyzed direct arylation

Recent progress in the discovery of small molecules for the treatment of amyotrophic lateral sclerosis (ALS)

• Allison S. Limpert,
• Margrith E. Mattmann and
• Nicholas D. P. Cosford

Beilstein J. Org. Chem. 2013, 9, 717–732, doi:10.3762/bjoc.9.82

• accumulation, respectively [30]. Metabolic profiling and further chemical modification were performed to increase the stability and potency of ASP derivatives, and this ultimately led to replacement of the thioether with an ether linkage and the identification of a new aryloxanyl pyrazolone (AOP) scaffold

• that the AOP scaffold is potentially suitable for therapeutic development for the treatment of ALS. Several important findings in the development of pyrazolone compounds included the identification of an N1-benzyl substituted pyrazolone, which displayed enhanced potency along with the discovery that

The tert- amino effect in heterocyclic chemistry: Synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives

• Dipak Prajapati and
• Kalyan Jyoti Borah

Beilstein J. Org. Chem. 2007, 3, No. 43, doi:10.1186/1860-5397-3-43

• malononitrile and cyanoacetamide followed by cyclisation using anhydrous zinc chloride. Background The N-phenyl-3-substituted 5-pyrazolone derivatives are organic compounds that have been known since 1883; they are very useful as intermediates for pharmaceuticals and are used as anti-inflammatory agents and

• allergy inhibitors.[1] Also, these 5-pyrazolone derivatives were investigated as thermal stabilizers for rigid PVC.[2][3] Therefore, large efforts have been directed towards the synthetic manipulation of pyrazolone derivatives to find more useful compounds.[4] In the heterocyclic area

• pyrazolone 1 under Vilsmeier conditions.[28] The 5-chloro atom of 2 is readily displaced by nucleophiles [29][30][31] and hence the reaction with several cyclic sec-amines (viz pyrrolidine, piperidine and morpholine) resulted in smooth conversion to the 5-tert-amino derivatives 3. These were then used in the