123532-18-3Relevant articles and documents
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.
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.
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.
