Microwave-assisted and solvent-free peroxidative oxidation of 1-phenylethanol to acetophenone with a CuII–TEMPO catalytic system

Abstract The water-soluble copper(II) complex [Cu(H2R)(HL)]∙H2O (1) was prepared by reaction of copper(II) nitrate hydrate with (E)-2-(((1-hydroxynaphthalen-2-yl)methylene)amino) benzenesulfonic acid (H2L) and diethanolamine (H3R). It was characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. 1 shows a high catalytic activity for the solvent-free microwave (MW) assisted oxidation of 1-phenylethanol with tert-butylhydroperoxide, leading, in the presence of TEMPO, to yields up to 85% (TON = 850) in a remarkably short reaction time (15 min, with the corresponding TOF value of 3.40 × 103 h− 1) under low power (25 W) MW irradiation

Complexes of copper(II) with 3-(ortho-substituted phenylhydrazo)pentane-2,4-diones: syntheses,properties and catalytic activity for cyclohexane oxidation

Reactions of copper(II) with 3-phenylhydrazopentane-2,4-diones X-2-C6H4-NHN = C{C(= O)CH3}(2) bearing a substituent in the ortho-position [X = OH (H2L1) 1, AsO3H2 (H3L2) 2, Cl (HL3) 3, SO3H (H2L4) 4, COOCH3 (HL5) 5, COOH (H2L6) 6, NO2 (HL7) 7 or H (HL8) 8] lead to a variety of complexes including the monomeric [CuL4(H2O)(2)]center dot H2O 10, [CuL4(H2O)(2)] 11 and [Cu(HL4)(2)(H2O)(4)] 12, the dimeric [Cu-2(H2O)(2)(mu-HL2)(2)] 9 and the polymeric [Cu(mu-L-6)](n)] 13 ones, often bearing two fused six-membered metallacycles. Complexes 10-12 can interconvert, depending on pH and temperature, whereas the Cu(II) reactions with 4 in the presence of cyanoguanidine or imidazole (im) afford the monomeric compound [Cu(H2O)(4){NCNC(NH2)(2)}(2)](HL4)(2)center dot 6H(2)O 14 and the heteroligand polymer [Cu(mu-L-4)(im)](n) 15, respectively. The compounds were characterized by single crystal X-ray diffraction (complexes), electrochemical and thermogravimetric studies, as well as elemental analysis, IR, H-1 and C-13 NMR spectroscopies (diones) and ESI-MS. The effects of the substituents in 1-8 on the HOMO-LUMO gap and the relative stability of the model compounds [Cu(OH)(L-8)(H2O)]center dot H2O, [Cu(L-1)(H2O)(2)]center dot H2O and [Cu(L-4)(H2O)(2)]center dot H2O are discussed on the basis of DFT calculations that show the stabilization follows the order: two fused 6-membered > two fused 6-membered/5-membered > one 6-membered metallacycles. Complexes 9, 10, 12 and 13 act as catalyst precursors for the peroxidative oxidation (with H2O2) of cyclohexane to cyclohexanol and cyclohexanone, in MeCN/H2O (total yields of ca. 20% with TONs up to 566), under mild conditions

Ultrasound and radiation-induced catalytic oxidation of 1-phenylethanol to acetophenone with iron-containing particulate catalysts

Este trabalho foi financiado pelo Concurso Anual para Projetos de Investigação, Desenvolvimento, Inovação e Criação Artística (IDI&CA) 2019 do Instituto Politécnico de Lisboa. Código de referência IPL/2019/STREAM_ISELIron-containingparticulatecatalystsof0.1–1 µmsizewerepreparedbywetandball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, whereas the mechanochemical method resulted in the formation of nonmagnetic microscale needles and rectangles. Catalytic activity of the prepared materials in the oxidation of 1-phenylethanol to acetophenone was assessed under conventional heating, microwave (MW) irradiation, ultrasound (US), and oscillating magnetic field of high frequency (induction heating). In general, the catalysts obtained by wet methods exhibit lower activities, whereas the materials prepared by ball milling afford better acetophenone yields (up to 83%). A significant increase in yield (up to 4 times) was observed under the induction heating if compared to conventional heating. The study demonstrated that MW, US irradiations, and induction heating may have great potential as alternative ways to activate the catalytic system for alcohol oxidation. The possibility of the synthesized material to be magnetically recoverable has been also verified.info:eu-repo/semantics/publishedVersio

Three-dimensional hydrogen-bonded supra­molecular assembly in tetrakis­(1,3,5-triaza-7-phosphaadamantane)copper(I) chloride hexa­hydrate

The structure of the title compound, [Cu(PTA)4]Cl·6H2O (PTA is 1,3,5-triaza-7-phosphaadamantane, C6H12N3P), is composed of discrete monomeric [Cu(PTA)4]+ cations, chloride anions and uncoordinated water mol­ecules. The CuI atom exhibits tetra­hedral coordination geometry, involving four symmetry-equivalent P–bound PTA ligands. The structure is extended to a regular three-dimensional supra­molecular framework via numerous equivalent O—H⋯N hydrogen bonds between all solvent water mol­ecules (six per cation) and all PTA N atoms, thus simultaneously bridging each [Cu(PTA)4]+ cation with 12 neighbouring units in multiple directions. The study also shows that PTA can be a convenient ligand in crystal engineering for the construction of supra­molecular architectures

Cooperative metal–ligand Assisted E/Z isomerization and cyano activation at CuII and CoII complexes of arylhydrazones of active methylene nitriles

New (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzoic acid (H2L4) and known sodium 2-(2-(dicyanomethylene)hydrazinyl)benzenesulfonate (NaHL1), 2-(2-(dicyano-methylene)hydrazinyl)benzoic acid (H2L2), and sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzenesulfonate (NaHL3) were used in the template synthesis of a series of CuII and CoII complexes [Cu(H2O)2L1a]·H2O (1), [Cu(H2O)(3-pyon)L1b]·H2O (2), [Cu(H2O)(4-pyon)L1b] (3), [Co(H2O)-((CH3)2NCHO)(μ-L2a)]2·(CH3)2NCHO (4), [Cu3(μ3-OH)-(NO3)(CH3OH)(μ2-X)3(μ2-HL3)] (5), [Cu(H2O)(py)L3]·H2O (6), [Cu(H2O)2(μ-L4)]6 ·6H2O (7), [Cu(2-cnpyb)2(L1b)2]·2H2O (8), [Cu(2-cnpya)2(L1a)2]·2H2O (9), and [Cu(H2O)(4-cnpy)(L1a)2] (10), where 3-pyon = 1-(pyridin-3-yl)ethanone, 4-pyon = 1-(pyridin-4-yl)ethanone, py = pyridine, HX = syn-2-pyridinealdoxime, 4-cnpy = 4-cyanopyridine; 2-cnpya, 2-cnpyb, L1a, L1b, L2a are the ligands derived from nucleophilic attack of methanol (a) or water (b) on a cyano group of 2-cyanopyridine (2-cnpy), L1 or L2, respectively, giving the corresponding iminoesters (2-cnpya, L1a or L2a) or carboxamides (2-cnpyb or L1b). An auxiliary ligand, namely syn-2-pyridinealdoxime or pyridine, acting cooperatively with the metal ion (CuII in this case), induced an E/Z isomerization of the H2L4 ligand; the E- and Z-isomers were isolated separately and fully characterized (compounds 9 and 10, respectively). A one-pot activation of nitrile groups in different molecules was achieved in the syntheses of 8 and 9. Complexes 1−10 are catalyst precursors for the solvent-free microwave (MW)-assisted selective oxidation of secondary alcohols to the corresponding ketones, with typical yields in the 29−99% range (TOFs up to 4.94 × 103 h−1) after 30 min of MW irradiation.info:eu-repo/semantics/publishedVersio