527-21-9Relevant articles and documents
Photoassisted catalytic cleavage of the C-F bond in pentafluorophenol with ZnO and the effect of operational parameters
Ravichandran, Lakshiminarasimhan,Selvam, Kaliyamoorthy,Swaminathan, Meenakshisundaram
, p. 951 - 956 (2007)
The photocatalytic cleavage of the C?F bond in pentafluorophenol (PFP) with ZnO using 254 and 365 nm UV light has been investigated under different conditions. The defluoridation was monitored using an ionometer with a fluoride ion selective electrode. The photocleavage was more effective under 254 nm than under 365 nm UV light. With 254 nm UV light, TiO2-P25, TiO 2 (anatase), ZnO, and ZrO2 photocatalyzed the deflouridation of PFP, whereas CdS, CdO, and SnO2 did not. The defluoridation is enhanced by the addition of oxidants such as KIO4, KClO3, (NH4)2S2O8, and KBrO3. The periodate ion is found to be the most efficient oxidant. The defluoridation intermediates were found to be tetrafluorodihydroxybenzene, trifluorotrihydroxybenzene, and tetrafluoroquinone. CSIRO 2007.
Polyoxometalate-based supramolecular porous frameworks with dual-active centers towards highly efficient synthesis of functionalized: P -benzoquinones
An, Haiyan,Chang, Shenzhen,Chen, Yanhong,Huang, Yaohui,Luo, Huiyun,Zhu, Qingshan
, p. 8591 - 8603 (2021/11/17)
Selective oxidation of substituted phenols is an ideal method for preparing functionalized p-benzoquinones (p-BQs), which serve as versatile raw materials for the synthesis of a variety of biologically active compounds. Herein, two new polyoxometalate-based supramolecular porous frameworks, K3(H2O)4[Cu(tza)2(H2O)]2[Cu(Htza)2(H2O)2][BW12O40]·6H2O (1) and H3K3(H2O)3[Cu(Htza)2(H2O)]3[SiW12O44]·14H2O (2) (Htza = tetrazol-1-ylacetic acid), were synthesized and structurally characterized by elemental analysis, infrared spectroscopy, thermal analysis, UV-vis diffuse reflectance spectroscopy, and single-crystal X-ray and powder diffraction. The single-crystal X-ray diffraction analysis indicates that both compounds possess unique petal-like twelve-nucleated Cu-organic units composed of triangular and hexagonal metal-organic loops. In 1, the Cu-organic units are isolated and [BW12O40]5- polyoxoanions are sandwiched between staggered adjacent triangular channels in the structure. However in 2, the Cu-organic units extend into a two-dimensional layered structure, and the [SiW12O44]12- polyoxoanions occupy the larger hexagonal channels in the stacked structure. Both compounds as heterogeneous catalysts can catalyze the selective oxidation of substituted phenols to high value-added p-BQs under mild conditions (60 °C) with TBHP as the oxidant, particularly in the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-p-benzoquinone (TMBQ, key intermediate in vitamin E production). Within 8-10 min, the yield of TMBQ is close to 100%, and oxidant utilization efficiency is up to 94.2% for 1 and 90.9% for 2. The turnover frequencies of 1 and 2 are as high as 5000 and 4000 h-1, respectively. No obvious decrease in the yield of TMBQ was observed after five cycles, which indicates the excellent sustainability of both compounds. Our study of the catalytic mechanism suggests that there is a two-site synergetic effect: (i) the copper ion acts as the catalytic site of the homolytic radical pathway; and (ii) the polyoxoanion acts as the active center of the heterolytic oxygen atom transfer pathway. This journal is
Catalytic defluorination of perfluorinated aromatics under oxidative conditions using N-bridged diiron phthalocyanine
Colomban, Cédric,Kudrik, Evgenij V.,Afanasiev, Pavel,Sorokin, Alexander B.
supporting information, p. 11321 - 11330 (2014/11/07)
Carbon-fluorine bonds are the strongest single bonds in organic chemistry, making activation and cleavage usually associated with organometallic and reductive approaches particularly difficult. We describe here an efficient defluorination of poly- and perfluorinated aromatics under oxidative conditions catalyzed by the μ-nitrido diiron phthalocyanine complex [(Pc)Fe III(μ-N)FeIV(Pc)] under mild conditions (hydrogen peroxide as the oxidant, near-ambient temperatures). The reaction proceeds via the formation of a high-valent diiron phthalocyanine radical cation complex with fluoride axial ligands, [(Pc)(F)FeIV(μ-N)FeIV(F) (Pc+?)], which was isolated and characterized by UV-vis, EPR, 19F NMR, Fe K-edge EXAFS, XANES, and Kβ X-ray emission spectroscopy, ESI-MS, and electrochemical techniques. A wide range of per- and polyfluorinated aromatics (21 examples), including C6F6, C6F5CF3, C6F5CN, and C6F5NO2, were defluorinated with high conversions and high turnover numbers. [(Pc)FeIII(μ-N)Fe IV(Pc)] immobilized on a carbon support showed increased catalytic activity in heterogeneous defluorination in water, providing up to 4825 C-F cleavages per catalyst molecule. The μ-nitrido diiron structure is essential for the oxidative defluorination. Intramolecular competitive reactions using C6F3Cl3 and C6F3H 3 probes indicated preferential transformation of C-F bonds with respect to C-Cl and C-H bonds. On the basis of the available data, mechanistic issues of this unusual reactivity are discussed and a tentative mechanism of defluorination under oxidative conditions is proposed.
