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Search for "pyrazole" in Full Text gives 130 result(s) in Beilstein Journal of Organic Chemistry.
Approaches towards the synthesis of 5-aminopyrazoles
- Ranjana Aggarwal,
- Vinod Kumar,
- Rajiv Kumar and
- Shiv P. Singh
Beilstein J. Org. Chem. 2011, 7, 179–197, doi:10.3762/bjoc.7.25
- reviewed in two books published in 1964 [5] and in 1967 [6]. Structurally simple 5-amino-1-tert-butylpyrazole-4-carboxamide I was found to inhibit p56 Lck [7] (Figure 1). 5-Amino-1-(4-methylphenyl) pyrazole II has been tested as an NPY5 antagonist [8]. 5-Amino-4-benzoyl-3-methylthio-1-(2,4,6
- -trichlorophenyl)pyrazole III has been reported as a potent corticotrophin-releasing factor-1 (CRF-1) receptor antagonist [9]. 5-Amino-1-(2,6-dichloro-4-(trifluoromethyl)phenyl)-4-(3-methoxyphenyl)-3-methylthiopyrazole IV has been described as a potent GABA inhibitor with selectivity towards insect versus
- herein report a detailed account of the synthetic methods available for 5-aminopyrazoles. As pyrazole derivatives do not exist in nature, probably, due to the difficulty in the construction of N–N bond by living organisms, their availability depends on the synthetic methods. A large number of synthetic
Graphical Abstract
Figure 1: Pharmacologically active 5-aminopyrazoles.
Scheme 1: General equation for the condensation of β-ketonitriles with hydrazines.
Scheme 2: Reaction of hydrazinoheterocycles with α-phenyl-β-cyanoketones (4).
Scheme 3: Condensation of cyanoacetaldehyde (7) with hydrazines.
Scheme 4: Synthesis of 5-aminopyrazoles and their sulfonamide derivatives.
Scheme 5: Synthesis of 5-aminopyrazoles, containing a cyclohexylmethyl- or phenylmethyl- sulfonamido group at...
Scheme 6: Regioselective synthesis of 3-amino-2-alkyl (or aryl) thieno[3,4-c]pyrazoles 19.
Scheme 7: Solid supported synthesis of 5-aminopyrazoles.
Scheme 8: Synthesis of 5-aminopyrazoles from resin supported enamine nitrile 25 as the starting material.
Scheme 9: Two-step “catch and release” solid-phase synthesis of 3,4,5-trisubstituted pyrazoles.
Scheme 10: Synthesis of pyrazolo[5,1-d][1,2,3,5]tetrazine-4(3H)-ones.
Scheme 11: Synthesis of the 5,5-ring system, imidazo[1,2-b]pyrazol-2-ones.
Scheme 12: Synthesis of 5-amino-3-(pyrrol-2-yl)pyrazole-4-carbonitrile.
Scheme 13: Synthesis of N-(1,3-diaryl-1H-pyrazol-5-yl)benzamide.
Scheme 14: Synthesis of 3,7-bis(arylazo)-6-methyl-2-phenyl-1H-imidazo[1,2-b]pyrazoles.
Scheme 15: Synthesis of 3,5-diaminopyrazole.
Scheme 16: Synthesis of 5-amino-4-cyanopyrazole and 5-amino-3-hydrazinopyrazole.
Scheme 17: Synthesis of 3,5-diaminopyrazoles with substituted malononitriles.
Scheme 18: Synthesis of 3,5-diamino-4-oximinopyrazole.
Scheme 19: Synthesis of 4-arylazo-3,5-diaminopyrazoles.
Scheme 20: Synthesis of 3- or 5-amino-4-cyanopyrazoles.
Scheme 21: Synthesis of triazenopyrazoles.
Scheme 22: Synthesis of 5(3)-aminopyrazoles.
Scheme 23: Synthesis of 3-substituted 5-amino-4-cyanopyrazoles.
Scheme 24: Synthesis of 2-{[(1-acetyl-4-cyano-1H-pyrazol-5-yl)amino]methylene}malononitrile.
Scheme 25: Synthesis of 5-aminopyrazole carbodithioates and 5-amino-3-arylamino-1-phenylpyrazole-4-carboxamide...
Scheme 26: Synthesis of 5-amino-4-cyanopyrazoles.
Scheme 27: Synthesis of thiazolylpyrazoles.
Scheme 28: Synthesis of 5-amino-1-heteroaryl-3-methyl/aryl-4-cyanopyrazoles.
Scheme 29: Synthesis of 5-amino-3-methylpyrazole-4-carboxamide.
Scheme 30: Synthesis of 4-acylamino-3(5)-amino-5(3)-arylsulfanylpyrazoles.
Scheme 31: Synthesis of 5-amino-1-aryl-4-diethoxyphosphoryl-3-halomethylpyrazoles.
Scheme 32: Synthesis of substituted 5-amino-3-trifluoromethylpyrazoles 114 and 118.
Scheme 33: Solid-support synthesis of 5-N-alkylamino and 5-N-arylaminopyrazoles.
Scheme 34: Synthesis of 5-amino-1-cyanoacetyl-3-phenyl-1H-pyrazole.
Scheme 35: Synthesis of 3-substituted 5-amino-1-aryl-4-(benzothiazol-2-yl)pyrazoles.
Scheme 36: Synthesis of 5-amino-4-carbethoxy-3-methyl-1-(4-sulfamoylphenyl)pyrazole.
Scheme 37: Synthesis of inhibitors of hsp27-phosphorylation and TNFa-release.
Scheme 38: Synthesis of the diglycylpyrazole 142.
Scheme 39: Synthesis of 5-amino-1-aryl-4-benzoylpyrazole derivatives.
Scheme 40: Synthesis of 4-benzoyl-3,5-diamino-1-(2-cyanoethyl)pyrazole.
Scheme 41: Synthesis of the 5-aminopyrazole derivative 150.
Scheme 42: Synthesis of 3,5-diaminopyrazoles 153.
Scheme 43: Synthesis of 5-aminopyrazoles derivatives 155 via lithiated intermediates.
Scheme 44: Synthesis of 5-amino-4-(1,2,4-oxadiazol-5-yl)-pyrazoles 157.
Scheme 45: Synthesis of a 5-aminopyrazole with anticonvulsant activity.
Scheme 46: Synthesis of tetrasubstituted 5-aminopyrazole derivatives.
Scheme 47: Synthesis of substituted 5-aminopyrazoles from hydrazonoyl halides.
Scheme 48: Synthesis of 3-amino-5-phenylpyrazoles from isothiazoles.
Scheme 49: Synthesis of 5-aminopyrazoles via ring transformation.
Michael-type addition of azoles of broad-scale acidity to methyl acrylate
- Sławomir Boncel,
- Kinga Saletra,
- Barbara Hefczyc and
- Krzysztof Z. Walczak
Beilstein J. Org. Chem. 2011, 7, 173–178, doi:10.3762/bjoc.7.24
- , no corresponding regioisomers were obtained. Keywords: imidazole derivatives; methyl acrylate; Michael-type addition; pyrazole derivatives; 1,2,4-triazole derivatives; Introduction Derivatives of azoles are important biologically active compounds. Many, especially those containing imidazole
- , pyrazole and 1,2,4-triazole moieties, constitute building blocks for a variety of therapeutic agents (Figure 1). 1,2-Arylimidazole derivatives, e.g., 2-(3-chloro-4-methylphenyl)-1-phenyl-4-(trifluoro-methyl)imidazole (I) are selective cyclooxygenase (COX-2) inhibitors [1]. Metronidazole (2-(2-methyl-5
- -3,5-diyl)diphenol (IV) and its derivatives are known modulators of receptors regulating the secretion of estrogens crucial in the pathogenesis of breast cancer [4]. 4-(Benzo[d][1,3]dioxol-5-ylmethyl)-1-(3-methoxybenzyl)-3-phenyl-pyrazole-5-carboxylic acid (V) is an antagonist of endothelial receptors
Graphical Abstract
Figure 1: Examples of azole derivatives as important therapeutic agents.
Scheme 1: Michael-type addition of azoles of broad-scale acidity 1a–h to methyl acrylate (2) under basic cond...
Scheme 2: Chemical evidence for a regioselective Michael-type addition of 4(5)-nitroimidazole (1c) to methyl ...
Molecular recognition of organic ammonium ions in solution using synthetic receptors
- Andreas Späth and
- Burkhard König
Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32
Graphical Abstract
Figure 1: Biologically important amines and quaternary ammonium salts: histamine (1), dopamine (2) and acetyl...
Figure 2: Crown ether 18-crown-6.
Figure 3: Conformations of 18-crown-6 (4) in solvents of different polarity.
Figure 4: Binding topologies of the ammonium ion depending on the crown ring size.
Figure 5: A “pseudorotaxane” structure consisting of 24-crown-8 and a secondary ammonium ion (5); R = Ph.
Figure 6: Typical examples of azacrown ethers, cryptands and related aza macrocycles.
Figure 7: Binding of ammonium to azacrown ethers and cryptands [111-113].
Figure 8: A 19-crown-6-ether with decalino blocking groups (11) and a thiazole-dibenzo-18-crown-6-ether (12).
Figure 9: 1,3-Bis(6-oxopyridazin-1-yl)propane derivatives 13 and 14 by Campayo et al.
Figure 10: Fluorescent azacrown-PET-sensors based on coumarin.
Figure 11: Two different pyridino-cryptands (17 and 18) compared to a pyridino-crown (19); chiral ammonium ion...
Figure 12: Pyridino-18-crown-6 ligand (21), a similar acridino-18-crown-6 ligand (22) and a structurally relat...
Figure 13: Ciral pyridine-azacrown ether receptors 24.
Figure 14: Chiral 15-crown-5 receptors 26 and an analogue 18-crown-6 ligand 27 derived from amino alcohols.
Figure 15: C2-symmetric chiral 18-crown-6 amino alcohol derivatives 28 and related macrocycles.
Figure 16: Macrocycles with diamide-diester groups (30).
Figure 17: C2-symmetric chiral aza-18-crown-6 ethers (31) with phenethylamine residues.
Figure 18: Chiral C-pivot p-methoxy-phenoxy-lariat ethers.
Figure 19: Chiral lariat crown ether 34.
Figure 20: Sucrose-based chiral crown ether receptors 36.
Figure 21: Permethylated fructooligosaccharide 37 showing induced-fit chiral recognition.
Figure 22: Biphenanthryl-18-crown-6 derivative 38.
Figure 23: Chiral lariat crown ethers derived from binol by Fuji et al.
Figure 24: Chiral phenolic crown ether 41 with “aryl chiral barriers” and guest amines.
Figure 25: Chiral bis-crown receptor 43 with a meso-ternaphthalene backbone.
Figure 26: Chromogenic pH-dependent bis-crown chemosensor 44 for diamines.
Figure 27: Triamine guests for binding to receptor 44.
Figure 28: Chiral bis-crown phenolphthalein chemosensors 46.
Figure 29: Crown ether amino acid 47.
Figure 30: Luminescent receptor 48 for bis-alkylammonium guests.
Figure 31: Luminescent CEAA (49a), a bis-CEAA receptor for amino acids (49b) and the structure of lysine bindi...
Figure 32: Luminescent CEAA tripeptide for binding small peptides.
Figure 33: Bis crown ether 51a self assembles co-operatively with C60-ammonium ion 51b.
Figure 34: Triptycene-based macrotricyclic dibenzo-[24]-crown-8 ether host 52 and guests.
Figure 35: Copper imido diacetic acid azacrown receptor 53a and the suggested His-Lys binding motif; a copper ...
Figure 36: Urea (54) and thiourea (55) benzo crown receptor for transport and extraction of amino acids.
Figure 37: Crown pyryliums ion receptors 56 for amino acids.
Figure 38: Ditopic sulfonamide bridged crown ether receptor 57.
Figure 39: Luminescent peptide receptor 58.
Figure 40: Luminescent receptor 59 for the detection of D-glucosamine hydrochloride in water/ethanol and lumin...
Figure 41: Guanidinium azacrown receptor 61 for simple amino acids and ditopic receptor 62 with crown ether an...
Figure 42: Chiral bicyclic guanidinium azacrown receptor 63 and similar receptor 64 for the enantioselective t...
Figure 43: Receptors for zwitterionic species based on luminescent CEAAs.
Figure 44: 1,10-Azacrown ethers with sugar podand arms and the anticancer agent busulfan.
Figure 45: Benzo-18-crown-6 modified β-cyclodextrin 69 and β-cyclodextrin functionalized with diaza-18-crown-6...
Figure 46: Receptors for colorimetric detection of primary and secondary ammonium ions.
Figure 47: Porphyrine-crown-receptors 72.
Figure 48: Porphyrin-crown ether conjugate 73 and fullerene-ammonium ion guest 74.
Figure 49: Calix[4]arene (75a), homooxocalix[4]arene (75b) and resorcin[4]arene (75c) compared (R = H, alkyl c...
Figure 50: Calix[4]arene and ammonium ion guest (R = H, alkyl, OAcyl etc.), possible binding sites; A: co-ordi...
Figure 51: Typical guests for studies with calixarenes and related molecules.
Figure 52: Lower rim modified p-tert-butylcalix[5]arenes 82.
Figure 53: The first example of a water soluble calixarene.
Figure 54: Sulfonated water soluble calix[n]arenes that bind ammonium ions.
Figure 55: Displacement assay for acetylcholine (3) with a sulfonato-calix[6]arene (84b).
Figure 56: Amino acid inclusion in p-sulfonatocalix[4]arene (84a).
Figure 57: Calixarene receptor family 86 with upper and lower rim functionalization.
Figure 58: Calix[6]arenes 87 with one carboxylic acid functionality.
Figure 59: Sulfonated calix[n]arenes with mono-substitution at the lower rim systematically studied on their r...
Figure 60: Cyclotetrachromotropylene host (91) and its binding to lysine (81c).
Figure 61: Calixarenes 92 and 93 with phosphonic acids groups.
Figure 62: Calix[4]arene tetraphosphonic acid (94a) and a double bridged analogue (94b).
Figure 63: Calix[4]arene tetraphosphonic acid ester (92c) for surface recognition experiments.
Figure 64: Calixarene receptors 95 with α-aminophosphonate groups.
Figure 65: A bridged homocalix[3]arene 95 and a distally bridged homocalix[4]crown 96.
Figure 66: Homocalix[3]arene ammonium ion receptor 97a and the Reichardt’s dye (97b) for colorimetric assays.
Figure 67: Chromogenic diazo-bridged calix[4]arene 98.
Figure 68: Calixarene receptor 99 by Huang et al.
Figure 69: Calixarenes 100 reported by Parisi et al.
Figure 70: Guest molecules for inclusion in calixarenes 100: DAP × 2 HCl (101a), APA (101b) and Lys-OMe × 2 HC...
Figure 71: Different N-linked peptido-calixarenes open and with glycol chain bridges.
Figure 72: (S)-1,1′-Bi-2-naphthol calixarene derivative 104 published by Kubo et al.
Figure 73: A chiral ammonium-ion receptor 105 based on the calix[4]arene skeleton.
Figure 74: R-/S-phenylalaninol functionalized calix[6]arenes 106a and 106b.
Figure 75: Capped homocalix[3]arene ammonium ion receptor 107.
Figure 76: Two C3 symmetric capped calix[6]arenes 108 and 109.
Figure 77: Phosphorous-containing rigidified calix[6]arene 110.
Figure 78: Calix[6]azacryptand 111.
Figure 79: Further substituted calix[6]azacryptands 112.
Figure 80: Resorcin[4]arene (75c) and the cavitands (113).
Figure 81: Tetrasulfonatomethylcalix[4]resorcinarene (114).
Figure 82: Resorcin[4]arenes (115a/b) and pyrogallo[4]arenes (115c, 116).
Figure 83: Displacement assay for acetylcholine (3) with tetracyanoresorcin[4]arene (117).
Figure 84: Tetramethoxy resorcinarene mono-crown-5 (118).
Figure 85: Components of a resorcinarene based displacement assay for ammonium ions.
Figure 86: Chiral basket resorcin[4]arenas 121.
Figure 87: Resorcinarenes with deeper cavitand structure (122).
Figure 88: Resorcinarene with partially open deeper cavitand structure (123).
Figure 89: Water-stabilized deep cavitands with partially structure (124, 125).
Figure 90: Charged cavitands 126 for tetralkylammonium ions.
Figure 91: Ditopic calix[4]arene receptor 127 capped with glycol chains.
Figure 92: A calix[5]arene dimer for diammonium salt recognition.
Figure 93: Calixarene parts 92c and 129 for the formation molecular capsules.
Figure 94: Encapsulation of a quaternary ammonium cation by two resorcin[4]arene molecules (NMe4+@[75c]2 × Cl−...
Figure 95: Encapsulation of a quaternary ammonium cation by six resorcin[4]arene molecules (NMe3D+@[130]6 × Cl−...
Figure 96: Structure and schematic of cucurbit[6]uril (CB[6], 131a).
Figure 97: Cyclohexanocucurbit[6]uril (CB′[6], 132) and the guest molecule spermine (133).
Figure 98: α,α,δ,δ-Tetramethylcucurbit[6]uril (134).
Figure 99: Structure of the cucurbituril-phthalhydrazide analogue 135.
Figure 100: Organic cavities for the displacement assay for amine differentiation.
Figure 101: Displacement assay methodology for diammonium- and related guests involving cucurbiturils and some ...
Figure 102: Nor-seco-Cucurbituril (±)-bis-ns-CB[6] (140) and guest molecules.
Figure 103: The cucurbit[6]uril based complexes 141 for chiral discrimination.
Figure 104: Cucurbit[7]uril (131c) and its ferrocene guests (142) opposed.
Figure 105: Cucurbit[7]uril (131c) guest inclusion and representative guests.
Figure 106: Cucurbit[7]uril (131c) binding to succinylcholine (145) and different bis-ammonium and bis-phosphon...
Figure 107: Paraquat-cucurbit[8]uril complex 149.
Figure 108: Gluconuril-based ammonium receptors 150.
Figure 109: Examples of clefts (151a), tweezers (151b, 151c, 151d) and clips (151e).
Figure 110: Kemp’s triacid (152a), on example of Rebek’s receptors (152b) and guests.
Figure 111: Amino acid receptor (154) by Rebek et al.
Figure 112: Hexagonal lattice designed hosts by Bell et al.
Figure 113: Bell’s amidinium receptor (156) and the amidinium ion (157).
Figure 114: Aromatic phosphonic acids.
Figure 115: Xylene phosphonates 159 and 160a/b for recognition of amines and amino alcohols.
Figure 116: Bisphosphonate recognition motif 161 for a colorimetric assay with alizarin complexone (163) for ca...
Figure 117: Bisphosphonate/phosphate clip 164 and bisphosphonate cleft 165.
Figure 118: N-Methylpyrazine 166a, N-methylnicotinamide iodide (166b) and NAD+ (166c).
Figure 119: Bisphosphate cavitands.
Figure 120: Bisphosphonate 167 of Schrader and Finocchiaro.
Figure 121: Tweezer 168 for noradrenaline (80b).
Figure 122: Different tripods and heparin (170).
Figure 123: Squaramide based receptors 172.
Figure 124: Cage like NH4+ receptor 173 of Kim et al.
Figure 125: Ammonium receptors 174 of Chin et al.
Figure 126: 2-Oxazolin-based ammonium receptors 175a–d and 176 by Ahn et al.
Figure 127: Racemic guest molecules 177.
Figure 128: Tripods based on a imidazole containing macrocycle (178) and the guest molecules employed in the st...
Figure 129: Ammonium ion receptor 180.
Figure 130: Tetraoxa[3.3.3.3]paracyclophanes 181 and a cyclophanic tetraester (182).
Figure 131: Peptidic bridged paraquat-cyclophane.
Figure 132: Shape-selective noradrenaline host.
Figure 133: Receptor 185 for binding of noradrenaline on surface layers from Schrader et al.
Figure 134: Tetraphosphonate receptor for binding of noradrenaline.
Figure 135: Tetraphosphonate 187 of Schrader and Finocchiaro.
Figure 136: Zinc-Porphyrin ammonium-ion receptors 188 and 189 of Mizutani et al.
Figure 137: Zinc porphyrin receptor 190.
Figure 138: Zinc porphyrin receptors 191 capable of amino acid binding.
Figure 139: Zinc-porphyrins with amino acid side chains for stereoinduction.
Figure 140: Bis-zinc-bis-porphyrin based on Tröger’s base 193.
Figure 141: BINAP-zinc-prophyrin derivative 194 and it’s guests.
Figure 142: Bisaryl-linked-zinc-porphyrin receptors.
Figure 143: Bis-zinc-porphyrin 199 for diamine recognition and guests.
Figure 144: Bis-zinc-porphyrin crown ether 201.
Figure 145: Bis-zinc-porphyrin 202 for stereodiscrimination (L = large substituent; S = small substituent).
Figure 146: Bis-zinc-porphyrin[3]rotaxane and its copper complex and guests.
Figure 147: Dien-bipyridyl ligand 206 for co-ordination of two metal atoms.
Figure 148: The ligand and corresponding tetradentate co-complex 207 serving as enantioselective receptor for a...
Figure 149: Bis(oxazoline)–copper(II) complex 208 for the recognition of amino acids in aqueous solution.
Figure 150: Zinc-salen-complexes 209 for the recognition tertiary amines.
Figure 151: Bis(oxazoline)–copper(II) 211 for the recognition of amino acids in aqueous solution.
Figure 152: Zn(II)-complex of a C2 terpyridine crown ether.
Figure 153: Displacement assay and receptor for aspartate over glutamate.
Figure 154: Chiral complex 214 for a colorimetric displacement assay for amino acids.
Figure 155: Metal complex receptor 215 with tripeptide side arms.
Figure 156: A sandwich complex 216 and its displaceable dye 217.
Figure 157: Lanthanide complexes 218–220 for amino acid recognition.
Figure 158: Nonactin (221), valinomycin (222) and vancomycin (223).
Figure 159: Monesin (224a) and a chiral analogue for enantiodiscrimination of ammonium guests (224b).
Figure 160: Chiral podands (226) compared to pentaglyme-dimethylether (225) and 18-crown-6 (4).
Figure 161: Lasalocid A (228).
Figure 162: Lasalocid derivatives (230) of Sessler et al.
Figure 163: The Coporphyrin I tetraanion (231).
Figure 164: Linear and cyclic peptides for ammonium ion recognition.
Figure 165: Cyclic and bicyclic depsipeptides for ammonium ion recognition.
Figure 166: α-Cyclodextrin (136a) and novocaine (236).
Figure 167: Helical diol receptor 237 by Reetz and Sostmann.
Figure 168: Ammonium binding spherand by Cram et al. (238a) and the cyclic[6]metaphenylacetylene 238b in compar...
Figure 169: Receptor for peptide backbone and ammonium binding (239).
Figure 170: Anion sensor principle with 3-hydroxy-2-naphthanilide of Jiang et al.
Figure 171: 7-bromo-3-hydroxy-N-(2-hydroxyphenyl)naphthalene 2-carboxamide (241) and its amine binding.
Figure 172: Naturally occurring catechins with affinity to quaternary ammonium ions.
Figure 173: Spiropyran (244) and merocyanine form (244a) of the amino acid receptors of Fuji et al.
Figure 174: Coumarin aldehyde (245) and its iminium species with amino acid bound (245a) by Glass et al.
Figure 175: Coumarin aldehyde appended with boronic acid.
Figure 176: Quinolone aldehyde dimers by Glass et al.
Figure 177: Chromogenic ammonium ion receptors with trifluoroacetophenone recognition motifs.
Figure 178: Chromogenic ammonium ion receptor with trifluoroacetophenone recognition motif bound on different m...
Pd/C-mediated synthesis of α-pyrone fused with a five-membered nitrogen heteroaryl ring: A new route to pyrano[4,3-c]pyrazol-4(1H)-ones
- Dhilli Rao Gorja,
- Venkateswara Rao Batchu,
- Ashok Ettam and
- Manojit Pal
Beilstein J. Org. Chem. 2009, 5, No. 64, doi:10.3762/bjoc.5.64
- Industrial Estate, Bollaram, Jinnaram Mandal, Medak District, Andra Pradesh 502 325, India present address: Institute of Life Sciences, University of Hyderabad Campus, Gachibowli, Hyderabad 500 046, Andhra Pradesh, India 10.3762/bjoc.5.64 Abstract Pd/C-mediated alkynylation of 5-iodo-pyrazole-4-carboxylic
- acid, involving the first regioselective construction of α-pyrone ring on a pyrazol moiety via tandem coupling–cyclization process, has been developed to afford pyrano[4,3-c]pyrazol-4(1H)-one in a single pot. Keywords: C–C bond; catalysis; palladium; pyrazole; pyrone; Introduction α-Pyrones [1][2
- shown anticancer properties in vitro [7]. Recently, incorporation of another five-membered ring, e.g. pyrazole pyrone moieties in a single molecule (A, Figure 1) has been reported to provide polycyclic azaheteroaromatics with a steroid-like skeleton [8]. This initiative was based on the assumption that
Graphical Abstract
Figure 1: Polycyclic azaheteroaromatics (A) and pyrano[4,3-c]pyrazol-4(1H)-ones (B).
Scheme 1: Pd/C-mediated synthesis of 6-substituted pyrano[4,3-c]pyrazol-4(1H)-ones 3.
Scheme 2: Preparation of 5-iodo-1-methyl-1H-pyrazole-4-carboxylic acid (1).
Scheme 3: Mechanism of ring closure of intermediate alkyne Z.
An easy synthesis of 5-functionally substituted ethyl 4-amino- 1-aryl- pyrazolo- 3-carboxylates: interesting precursors to sildenafil analogues
- Said A. S. Ghozlan,
- Khadija O. Badahdah and
- Ismail A. Abdelhamid
Beilstein J. Org. Chem. 2007, 3, No. 15, doi:10.1186/1860-5397-3-15
- arylhydrazononitriles 1a-c are valuable precursors to 4-amino-5-substituted-1-aryl-1H-pyrazole-3-carboxylic acid ethyl ester which can be used for preparation of sildenafil analogues. synthesis of Ethyl 4-amino-5-substituted-1-aryl-1H-pyrazole-3-carboxylates (4) Reactivity of pyrazole 4b with phenylisothiocyanate and
- acetic anhydride Conversion of pyrazole 4b Ethyl into pyrazolo[4,3-d]pyrimidine-3-carboxylate 10 Conversion of arylhydrazononitriles 1 into 3-Amino-4-arylhydrazono-4H-isoxazol-5-one Supporting Information Supporting Information File 16: The experimental section. The experimental data and the results of
Graphical Abstract
Scheme 1: synthesis of Ethyl 4-amino-5-substituted-1-aryl-1H-pyrazole-3-carboxylates (4)
Scheme 2: Reactivity of pyrazole 4b with phenylisothiocyanate and acetic anhydride
Scheme 3: Conversion of pyrazole 4b Ethyl into pyrazolo[4,3-d]pyrimidine-3-carboxylate 10
Scheme 4: Conversion of arylhydrazononitriles 1 into 3-Amino-4-arylhydrazono-4H-isoxazol-5-one
