2- Phenyl-5-substituted pyrazol-3-ones

More recently, Tietze and Steinmetz (96SL667) used the patented polystyrene-resin methodology for for the solid-phase synthesis of a large number of diverse )3-keto esters 40a-h. These were reacted with phenylhydrazine in THF at room temperature to give hydrazones 41a-h that were then cychzed into 2-phenyl 5-substituted pyrazol-3-ones 42a-h by heating in toluene at 1(X)°C (Scheme 12). 

Hydrazones are also useful substrates in the preparation of pyrazoles. Reaction of N-monosubstituted hydrazones with nitroolefins led to a regioselective synthesis of substituted pyrazoles <060L3505>. lf/-3-Ferrocenyl-l-phenylpyrazole-4-carboxaldehyde was achieved by condensation of acetylferrocene with phenylhydrazine followed by intramolecular cyclization of the hydrazone obtained under Vilsmeier-Haack conditions <06SL2581>. A one-pot synthesis of oxime derivatives of l-phenyl-3-arylpyrazole-4-carboxaldehydes has been accomplished by the Vilsmeier-Haack reaction of acetophenone phenylhydrazones <06SC3479>. 

Just as with nondoped red fluorescent dyes, nondoped phosphorescent iridium complexes consisting of two chelating phenyl-substituted quinazoline and one (2-pyridyl) pyrazolate or triazolate have recently been reported by Chen et al. (278-280) (Scheme 3.88) [308]. All of these complexes exhibited bright red phosphorescence with relatively short excited state lifetimes of 0.4-1.05 ps. PHOLEDs fabricated using the compounds A and B with relatively... 

A convenient method to obtain 3-amino-5-trifluoromethyl-l//-pyrazoles by cyclocondensation of 4-amino-4-ethoxy-l,l,l-trifluorobut-3-en-2-ones with hydrazine and phenylhydrazine has been reported <2006SL1485>. Trifluoromethylated pyrazoles were synthesized from trifluoromethylenaminones and monosubstituted hydrazines <2004JFC(125)1299>. 5-Amino-3-phenylpyrazoles 534 were prepared from a-oxoketene 0,W-acetals 533 using montmor-illonite K-10 under sonication conditions (Equation 108) <200381160>. 3-Amino-l-(/)-phenyl-substituted)-2-buten-l-ones... 

The introduction of a carbonyl carbamate group at position 4 of the pyrazol-3-one ring can be done directly by fusion of appropriately 2-substituted /i-keto ester with a hydrazine (04TJC659) (Scheme 16). The jS-keto ester 67 was synthesized in two steps from ethyl 4,5-dioxo-2-phenyl-4,5-dihydrofuran-3-carboxylate 65 by decarbonylation to ethoxy-carbonylbenzoylketene intermediate 66 in refluxing benzene and then nucleophilic addition by methyl carbamate. Ethyl 2-benzoyl-3-[(methoxy-carbonyl)amino]-3-oxopropanoate 67 with diphenylhydrazine on heating in benzene gave 4-substituted pyrazol-3-one 68 in 44% yield. 

Several reports describe the reaction of pyrazol-3-ones with amidines and iminium salts where the group displaced is an amine. Nucleophilic substitution of ammonia by 2,5-dimethylpyrazol-3-one 591 attack on benzamidine hydrochloride 592 requires 220 °C to give via addition intermediate 593 4-[imino(phenyl)methyl]pyrazol-3-one... 

Shelke et al. [80] S5mthesized various fluorine-containing compounds by conventional and nonconventional procedures by ultrasonication and microwave techniques. Various 3-substituted-l-phenyl-lH-pyrazole-4-carbaldehydes were treated with 3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one (83) to give 4-((3-(4-aryl)-l-phenyl-lH-pyrazol-4-yl) methylene)-3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one (85). Equivalent mole of 3-formylchromone and 3-(trifluoromethyl)-l-phenyl-lH-pyrazol-5(4H)-one by conventional method and nonconventional methods gave 3-(trifluoromethyl)-4-(4-oxo-4H chromon-3-yl)-methylene-l-phenyl-lH-pyrazol-(4H)-one (84) (Scheme 21). Compounds 84 and 85 were obtained in slightly better yields within 5-10 min under ultrasonication than in 2-3 min with microwave irradiation. 

Ivanova, B.B., A. Chapkanov, M. Arnaudov, and I.K. Petkov. 2005. IR-LD spectral study and ab initio calculations of 1-phenyl 3-substituted pyrazol-5-ones. Struct. Chem. 16 47-53. 

It is of interest to note that these were not the first benzoates substituted in the ortho position with a heterocyclic ring to show effects in plants. Invariably, however, in these earlier cases the heterocyclic ring was an aromatic one such as a pyrazole or oxazole substituted with a phenyl group ( -4). 

In the case of 5-bromo-3,4-dimethyl-l-phenyl-l/f, 6//-pyrano[2,3-c]pyrazol-6-one (59), mixed acid nitration results not only in para substitution in the phenyl ring, but also in ipso attack at the 5-position to yield... 

Pyrazol-5-ones are widely used in medicine, color photography, analytical chemistry, and agriculture. The tautomeric equilibria between the CFI, OH, and NH forms in a series of 4-substituted-l-phenyl-3-methyl-pyrazolin-5-ones 100-102 have been studied using ab initio calculations at various levels of theory and comparison made with the experimental results obtained from C NMR measurements <2001JP0566>. The tautomerism of 4-acyl-2-phenyl-2-pyrazolidin-3-ones 103 and 104 was studied by C NMR spectroscopy <1999CHE748>. The tautomerism of... 

The ring contraction of pyridazinones to pyrazoles has been further in-vestigated. l-Phenyl-4,5-disubstituted pyridazin-6-ones are transformed with hot alkali into pyrazoles (264), accompanied sometimes by other substituted pyridazines. Unexpectedly, l-phenyl-4-methylthio-5-chloro-pyridazin-6-one gave in addition to 264 also another pyridazine [Eq. (31)], which originates by the attack of the liberated methylthio anion on the starting compound. 

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