A Tri-Coordinate-Magnesium Silylamide Complex: {[(CH3)3Si]2N}2MgO(CH2CH2)2OMg{N[Si(CH3)3]2}2

The reaction of diethylmagnesium dioxane adduct solution with 1,1,1,3,3,3-hexamethyldisilazan ((CH₃)₃SiNHSi(CH₃)₃) gives {[(CH₃)₃Si]₂N}₂MgO(CH₂CH₂)₂OMg{N[Si(CH₃)₃]₂}₂ (1); this alkoxomagnesium silylamide in the solid state contains unprecedented three-coordinate magnesium and oxygen atoms.     

Synthesis and antimicrobial activity of some new coumarin and dicoumarol derivatives

PTC reaction of coumarin derivative 1 with alkyl halides afforded C₄ oxygen alkylation products 2a-d in appreciative yield, whereas with phenyl isothiocyanate gives the C₃ addition product 4 ; also, one-pot three-component PTC reaction was investigated. Treatment of coumarin 1 with aromatic aldehydes in different molar ratios gives 3-arylidene derivatives 7a,b and the dicoumarol derivatives 8a,b . Pyrano chromene 9 and pyrano pyridine 10 were obtained by reaction of arylidene 7a with ethyl acetoacetate through Michael cycloaddition reaction. The stability of pyrone ring in 3-arylidene 7 and dicoumarol 8 towards different nucleophilic reagents under reflux and/or fusion conditions has been studied by the action of hydrazine hydrate, ammonium acetate, methyl amine, and p-toluidine afforded compounds 11 and 13a-c . The antimicrobial activity of some synthesized compounds has been investigated.     

Nickel (II) complexes supported by a fluorinated β‐diketiminate backbone ligand: synthesis,catalytic activity toward norbornene polymerization,and the oxygenated species

The reaction of the lithium salt of backbone fluorinated β‐diketiminate ligands, ArNC(CF₃)CHC(CF₃) NArLi, with trans‐[NiCl(Ph)(PPh₃)₂] gives nickel (II) complexes, ArNC(CF₃)CHC(CF₃)NAr(Ph) (PPh₃)Ni (Ar = 2, 6‐Me₂C₆H₃: 1 ; 2, 6‐ⁱPr₂C₆H₃: 2 ). When activated by methylaluminoxane (MAO), both complexes polymerize norbornene rapidly via a vinyl‐type polymerization mechanism. Treatment of nickel complex 1 with oxygen gives rise to intramolecular aerobic hydroxylation. The oxygenated species 3 was characterized by X‐ray crystallography. Copyright © 2006 John Wiley & Sons, Ltd.     

Copper-catalyzed domino reaction between 1-(2-halophenyl)methanamines and amidines or imidates for the synthesis of 2-substituted quinazolines

The CuI-catalyzed domino reaction between 1-(2-bromophenyl)methanamines and amidines using K₃PO₄ as the base, pivalic acid as the additive, and aerial oxygen as the oxidant gives access to substituted quinazolines in a single step with yields in the range between 43 and 90%. It is assumed that the reaction proceeds as a Cu(I)-catalyzed intermolecular N-arylation followed by an intramolecular nucleophilic substitution and a Cu(II)-catalyzed oxidation. The amidines can be replaced with imidates and the reaction can also be run with 1-(2-iodophenyl)methanamine.     

Synthesis and Structure of Tetraphenylantimony Nitrate

The reaction of pentaphenylantimony with triphenylantimony dinitrate in toluene gives tetraphenylantimony nitrate in 99% yield. The X-ray diffraction data show that the antimony atom in the molecule of tetraphenylantimony nitrate has a distorted trigonal-bipyramidal coordination with axial location of the oxygen atom of the nitrate group. The Sb-O, Sb_{a x}, and Sb-C_{e q} bond lengths in two independent molecules of tetraphenylantimony nitrate are 2.498(3), 2.548(2); 2.134(3), 2.138(3); and 2.101(3)-2.112 Å.     

Efficient copper-catalyzed N-arylation of NH-containing heterocycles and sulfonamides with arenediazonium tetrafluoroborates

A practical copper-catalyzed N-arylation of NH-containing heterocycles with arenediazonium tetrafluoroborates has been developed using CuCl as catalyst and K₂CO₃ as additive under ligand-free conditions. This reaction system has wide substrate scope including imides, 1H-pyrazole, 1H-tetrazoles, 1,2-benzisothiazol-3(2H)-one, and related sulfonamides and gives moderate to excellent yields (up to 95%) of the desired products. This strategy is very general, simple, environmentally friendly, and tolerant of oxygen.     

An unexpected course of the Meisenheimer reaction : aryl phosphates in the reaction of phosphoryl chloride with 2, 3-diphenylquinoxaline-N1-oxide.

Contrary to what is observed with other π-deficient heteroaromatic N-oxides, the reaction of 2, 3-diphenylquinoxaline-N₁-oxide with OPCl₃ gives only very poor yields of chlorinated quinoxalines. It is shown that the major product arises from an unprecedented attack by the nucleophilic oxygen atom of the reagent at a carbon atom of the homocycle of the O-phosphorylated N-oxide, leading ultimately to the corresponding mono- (or di-) aryl ester of phosphoric acid. Using a much smaller excess of OPCl₃ and dilution of the medium with an inert solvent strongly increase the yield of chlorination products.     

Kinetics of the reaction between 1,3-diphenylisobenzofuran and nitrogen dioxide studied by steady-state fluorescence

1,3-Diphenylisobenzofuran (DPBF) is a fluorescent molecule which is believed to react highly specifically toward reactive oxygen species such as singlet oxygen (¹O₂), hydroxy (HO^·), alkyloxy (RO^·), and alkylperoxy (ROO^·) radicals. In all cases the reaction product is 1,2-dibenzoylbenzene. In order to prove that DPBF gives the same product in contact with reactive nitrogen species, its reaction with nitrogen dioxide radical has been studied in 2,2,4-trimethylpentane using the steady-state fluorescence method and mass spectrometry. The progress of the studied reaction was measured by observation of changes in fluorescence intensity of DPBF after addition of nitrogen dioxide (NO₂). The rate constants of DPBF fluorescence decay affected by NO₂ have been determined. Experiments were conducted over the temperature range of 13–37 °C and for NO₂ concentrations from 0.02 to 0.14 mmol dm^?3. It has been found that the reaction between 1,3-diphenylisobenzofuran and nitrogen dioxide proceeds in two steps. The first step is a very rapid reaction whose rate could not be measured under established experimental conditions. The second step is slower. The reaction product was identified by registration of mass spectra. The probable reaction mechanism is proposed.     

Multiple bonds between main group elements and transition metals: LXIX. Condensation reactions of methyltrioxorhenim with 8-hydroxyquinoline and 2-hydroxyaniline: new rhenium(VII) chelate complexes

The title compound methyltrioxorhenium, (CH₃ReO₃,1), reacts with 8-hydroxyquinoline at room temperature to give the dinuclear Re^VII complex [CH₃Re(O)₂(8-oxyquinoline)]₂O (2) in 90% yield. A single crystal X-ray diffraction study has shown that2 has a dimeric octahedral structure with a total of four terminal oxo ligands and one bridging oxygen atom. By contrast, the more complex condensation reaction of1 with 2-hydroxyaniline gives the mononuclear Re^VII compound CH₃Re(O)(2-OC₆H₄NH)₂ (3) in 60% yield.     

Gas‐Phase Reaction of CeV2O7+ with C2H4: Activation of CC and CH Bonds

The reactivity of metal oxide clusters toward hydrocarbon molecules can be changed, tuned, or controlled by doping. Cerium‐doped vanadium cluster cations CeV₂O₇⁺ are generated by laser ablation, mass‐selected by a quadrupole mass filter, and then reacted with C₂H₄ in a linear ion trap reactor. The reaction is characterized by a reflectron time‐of‐flight mass spectrometer. Three types of reaction channels are observed: 1) single oxygen‐atom transfer , 2) double oxygen‐atom transfer , and 3) C?C bond cleavage. This study provides the first bimetallic oxide cluster ion, CeV₂O₇⁺, which gives rise to C?C bond cleavage of ethene. Neither Ce_xO_y^± nor V_xO_y^± alone possess the necessary topological and electronic properties to bring about such a reaction.     

Synthesis of 3-Phenyl and 5-Phenyl-2-pyrrolidinone via Rhodium Catalysed Carbonylation of Allylamines

The Rh₄(CO)₁₂ catalysed reaction with CO and H₂ of 1-phenyl- and 3-phenyl allylamine gives 5-phenyl- and 3-phenyl-2-pyrrolidinone respectively, in good yield. A reasonable reaction pathway of the carbonylation reaction is presented.     

Cu(I)/Fe(III) promoted dicarbonylation of aminopyrazole via oxidative CH coupling with methyl ketones

Cu(I)/Fe(III) promoted C4-dicarbonylation of 5-aminopyrazole is developed. The strategy involved radical triggered direct oxidative coupling of 5-aminopyrazoles with methyl ketones using aerial oxygen as a source of oxygen in newly generated carbonyl group. CuI is used as catalyst and FeCl₃·6H₂O is used as additive and the reaction proceeded at 120?°C in DMSO for 9–12?h. It is found that use of Cu(II) catalyst gives the thiomethylated product by reacting with DMSO instead of oxidative coupling. A plausible mechanism is also given.     

Über die Umsetzung von Adipinsäurediamid mit Phosphorpentachlorid

Reaction of Adipic Acid Diamide with Phosphorus Pentachloride The reaction of adipamide (I) with phosphorus pentachloride in a solvent leads to (Cl₃P?NCCl₂CCl₂CH₂)₂ (II). The stages of the reaction are: 1. chlorination of the keto and methylen groups 2. formation of the ? N?PCl₃ group. This result is a supplement of the existing conception about the course of the reaction of carboxylic acid amides with phosphorus pentachloride. The reaction of (I) with PCl₅ without any solvent has been reproduced and the course of reaction has also been investigated. This reaction gives mainly NC(CH₂)₄CN. The resulting product of a careful hydrolysis of (II) is (Cl₂OPN?CClCl₂CH₂)₂. A total hydrolysis gives back (I).     

Komplexe des 2-(Trimethylsiloxy)phenylisocyanids als Vorstufen für die Darstellung von N,O-Heterocarben-Komplexen

The reaction of 2-(trimethylsiloxy)phenylisocyanide 1 with PdI₂ or CoI₂ leads to the square-planar complex trans-[Pd(l)₂I₂] 2 and the octahedral complex trans-[CO(1₄I₂] 3, respectively. Both 2 and 3 were characterized by X-ray structure analysis. Cleavage of the Si-O bond gives complexes with coordinated 2-hydroxyphenylisocyxanide ligands which rearrange via an intramolecular nucleophilic attack of the hydroxyl oxygen at the isocyanide carbon to give complexes with cyclic N,O-heterocarbene ligands.     

Organotellurium(IV) complexes: synthesis and molecular structure of 2,6-diacetylpyridine (C,N,O) tellurium(IV) trichloride

The reaction of TeCl₄ with 2,6-diacetylpyridine in methylene chloride or tetrahydrofuran gives a new type of organotellurium (IV) compound. An X-ray structure determination showed that the organic radical bonds to the tellurium as a tridentate ligand via a methylene carbon of one of the acetyl groups, the pyridine nitrogen, and the carbonyl oxygen of the second acetyl group. Analogous organotellurium trichloride complexes involving C,O coordination have been formulated for the condensation products of TeCl₄ with 2-acetylcyclohexanone and 3-acetyl-7-methoxycoumarin, while C,N coordination occurs in the condensation product of TeCl₄ and 2-acetylpyridine.     

Selective Hydrogen Oxidation in the Presence of C3 Hydrocarbons Using Perovskite Oxygen Reservoirs

Perovskite‐type oxides, ABO₃, can be successfully applied as solid “oxygen reservoirs” in redox reactions such as selective hydrogen combustion. This reaction is part of a novel process for propane oxidative dehydrogenation, wherein the lattice oxygen of the perovskite is used to combust hydrogen selectively from the dehydrogenation mixture at 550 °C. This gives three key advantages: it shifts the dehydrogenation equilibrium to the side of the desired products, heat is generated, thus aiding the endothermic dehydrogenation, and it simplifies product separation (H₂O vs H₂). Furthermore, the process is safer since it uses the catalysts’ lattice oxygen instead of gaseous O₂. We screened fourteen perovskites for activity, selectivity and stability in selective hydrogen combustion. The catalytic properties depend strongly on the composition. Changing the B atom in a series of LaBO₃ perovskites shows that Mn and Co give a higher selectivity than Fe and Cr. Replacing some of the La atoms with Sr or Ca also affects the catalytic properties. Doping with Sr increases the selectivity of the LaFeO₃ perovskite, but yields a catalyst with low selectivity in the case of LaCrO₃. Conversely, doping LaCrO₃ with Ca increases the selectivity. The best results are achieved with Sr‐doped LaMnO₃, with selectivities of up to 93 % and activities of around 150 μmol O m^?2. This catalyst, La_0.9Sr_0.1MnO₃, shows excellent stability, even after 125 redox cycles at 550 °C (70 h on stream). Notably, the activity per unit surface area of the perovskite catalysts is higher than that of doped cerias, the current benchmark of solid oxygen reservoirs.     

Backbone Reactivity of Lithium β-Diketiminate (NacNac) Complexes with CO2, tBuNCO and iPrNCO

Though alkali metal NacNac (β-diketiminate) complexes have been utilised in synthesis as NacNac-transfer agents, studies of them in their own right with small molecules are exceptionally rare. Here, the lithium compound of the common 2,6-diisopropylphenyl-β-methyldiketiminate [NacNac(Dipp, Me)] ligand is investigated with carbon dioxide and isocyanates. In all four cases reaction occurs at the backbone γ-C atom of the NacNac ligand, which redistributes electronically into a diimine. Insertion of CO₂ gives an eight-atom carboxylate (Li₂O₄C₂) ring at the γ-C site in a dimer. Insertion of tBuNCO gives a secondary amide at the γ-C site in a monomer with TMEDA chelating lithium. Double insertion of tBuNCO and (adventitious) oxygen gives a dimer with a (LiO)₂ central core involving the latter source. Insertion of less bulky (iPrNCO) gives a dimer with dimerisation through the C=O bonds of the emergent secondary amide function.     

Umsetzungen von 1-Aminoalkan-1,1-diphosphonsäuren mit salpetriger Säure

Reactions of 1-Aminoalkane-1,1-diphosphonic Acids with Nitrous Acid Compounds of the structure RC(NH₂)(PO₃H₂)₂ 1 give products RC(OH)(PO₃H₂)₂ 2 in high yields by the reaction with nitrous acid. In contrast, when R = Aryl the reaction of 1 often gives in concentrated hydrochloric acid RCCl(PO₃H₂)₂ 3 . Exceptions to the above reaction are described.