123532-18-3Relevant academic research and scientific papers
New ultraviolet stabilizers: 3- and 5-(2′-hydroxyphenyl)pyrazoles
Catalán, Javier,Fabero, Fernando,Claramunt, Rosa M.,Dolores Santa Maria,De la Concepción Foces-Foces,Cano, Felix Hernández,Martínez-Ripoll, Martín,Elguero, José,Sastre, Roberto
, p. 5039 - 5048 (1992)
A new class of ultraviolet stabilizers, the C-(2?-hydroxyphenyl)pyrazoles, is described. The combined use of X-ray crystallography [3(5)-(2′-hydroxyphenyl)pyrazole (5), l-methyl-3-(2′-hydroxyphenyl)pyrazole (7), and 1-methyl-5-(2?-hydroxyphenyl)pyrazole (8)], NMR (1 and 13C), and UV spectroscopies allows the determination of the major tautomers, the coplanarity of both rings if present, and the existence of hydrogen bonds. Compounds 5 and 7, in which there is an intramolecular hydrogen bond (IMHB), do not fluoresce in cyclohexane. Solvent and temperature experiments prove that for these compounds in cyclohexane proton transfer took place in the excited singlet state but not in the triplet state (phosphorescence) and that the latter one is of higher energy than the former. The fact that the absorptions of planar 1-methyl-3-(2′-methoxyphenyl)pyrazole (9) and nonplanar 1-methyl-5-(2′-methoxyphenyl)pyrazole (10) are quite different whereas their emissions are very similar suggests that 10 might behave as a laser dye in the UV region (from an excited planar form to a ground state nonplanar form). Finally, the photostability of (2'-hydroxyphenyl)- and (2′-methoxyphenyl)pyrazoles was determined, compound 7 being even more stable than Tinuvin P.
Regioselective Synthesis of C3-Hydroxyarylated Pyrazoles
O'Sullivan, Leonie,Patel, Ketul V.,Rowley, Ben C.,Brownsey, Duncan K.,Gorobets, Evgueni,Gelfand, Benjamin S.,Van Humbeck, Jeffrey F.,Derksen, Darren J.
, p. 846 - 854 (2021/12/27)
Pyrazoles are ubiquitous structures in medicinal chemistry. We report the first regioselective route to C3-hydroxyarylated pyrazoles obtained through reaction of pyrazole N-oxides with arynes using mild conditions. Importantly, this method does not requir
Nickel-catalyzed Suzuki-Miyaura couplings in green solvents
Ramgren, Stephen D.,Hie, Liana,Ye, Yuxuan,Garg, Neil K.
supporting information, p. 3950 - 3953 (2013/09/02)
The nickel-catalyzed Suzuki-Miyaura coupling of aryl halides and phenol-derived substrates with aryl boronic acids using green solvents, such as 2-Me-THF and tert-amyl alcohol, is reported. This methodology employs the commercially available and air-stable precatalyst, NiCl2(PCy 3)2, and gives biaryl products in synthetically useful to excellent yields. Using this protocol, bis(heterocyclic) frameworks can be assembled efficiently.
Dioxomolybdenum(VI) complexes with pyrazole based aryloxide ligands: Synthesis, characterization and application in epoxidation of olefins
Schachner, J?rg A.,Traar, Pedro,Sala, Chris,Melcher, Michaela,Harum, Bastian N.,Sax, Alexander F.,Volpe, Manuel,Belaj, Ferdinand,M?sch-Zanetti, Nadia C.
, p. 7642 - 7649 (2012/09/05)
Synthesis, characterization, and epoxidation chemistry of four new dioxomolybdenum(VI) complexes [MoO2(L)2] (1-4) with aryloxide-pyrazole ligands L = L1-L4 is described. Catalysts 1-4 are air and moisture stable and easy to synthesize in only three steps in good yields. All four complexes are coordinated by the two bidentate ligands in an asymmetric fashion with one phenoxide and one pyrazole being trans to oxo atoms, respectively. This is in contrast to the structure found for the related aryloxide-oxazoline coordinated Mo(VI) dioxo complex 5. This was confirmed by the determination of the molecular structures of complexes 1-3 by X-ray diffraction analyses. Compounds 1-4 show high catalytic activities in the epoxidation of various olefins. Cyclooctene (S1) is converted to its epoxide with high activity, whereas the epoxidation of styrene (S2) is unselective. Internal olefins (S3 and S4) are also acceptable substrates, as well as the very challenging olefin 1-octene (S5). Catalyst loading can be reduced to 0.02 mol % and the catalyst can be recycled up to ten times without significant loss of activity. Supportive DFT calculations have been carried out in order to obtain deeper insights into the electronic situation around the Mo atom.
A facile access to a novel bidentate enantiomerically pure P,N-donor ligand
Seubert, Christoph K.,Sun, Yu,Thiel, Werner R.
experimental part, p. 4971 - 4977 (2009/09/30)
The synthesis of a new chiral P,N-donor ligand containing a phosphite and a pyrazole site and its coordination chemistry with transition metals are described. The Royal Society of Chemistry 2009.
INVESTIGATIONS IN THE CHROMONE SERIES. PART XVI. REACTIONS OF CHROMONE DERIVATIVES AND 4-THIOCHROMONE WITH METHYLHYDRAZINE
Nawrot-Modranka, Jolanta,Kostka, Krzysztof
, p. 103 - 111 (2007/10/02)
The transformations of 2-methyl-, 2-ethyl- and 2-phenylchromone and 4-thiochromone, 2-methyl- and 8-methyl-4-thiochromone with methylhydrazine were studied.Two series of pyrazoles, A and B, were obtained.The transformations of methyl- and phenylhydrazine with enamino ketones (chromone transformation products) confirmed the course of transformations of chromone derivatives with methylhydrazine.
STUDIES OF CHROMONE DERIVATIVES. PART XV. REACTIONS OF CHROMONE AND ITS DERIVATIVES WITH METHYLHYDRAZINE
Nawrot-Modranka, Jolanta,Kostka, Krzysztof
, p. 417 - 426 (2007/10/02)
The transformations of chromone, 6-methyl-, 6-nitro-, and 8-methylchromone with methylhydrazine have been studied.Two series of pyrazoles (A and B) were obtained and transformation intermediates have been isolated.The structure of these compounds has been established and the reaction course of chromone and its derivatives with methylhydrazine is proposed.
