Hexanuclear copper(II) cages built on a central {μ3-O···H···μ3-O} moiety, 1,3-bis(dimethylamino)-2-propanolato and capping R-phosphonates: crystal structures, magnetic behavior, and DFT studies

The syntheses, structural characterization, and magnetic behavior of two new hexanuclear copper(II) complexes derived from R-phosphonic acids and 1,3-bis(dimethylamino)-2-propanol (Hbdmap) with formulas [Cu(6)(μ-bdmap)(3)(μ(3)-Ph-PO(3))(2)(μ(3)-O···H···μ(3)-O)(ClO(4))(2)(H(2)O)]·5H(2)O (1) and [Cu(6)(μ-bdmap)(3)(μ(3)-t-Bu-PO(3))(2)(μ(3)-O···H···μ(3)-O)(μ(1,3)-dca)(dca)(H(2)O)]·6H(2)O (2) (Ph-H(2)PO(3) = phenylphosphonic acid, t-Bu-H(2)PO(3) = tert-butylphosphonic acid, dca = dicyanamide) are reported. Compounds 1 and 2 are hexanuclear 3.111 R-phosphonate(2-)/1,3-bis(dimethylamino)-2-propanolato(1-) cages including in the center the [μ(3)-O···H···μ(3)-O](3-) unit. The temperature dependence of the magnetic properties of 1 and 2 clearly indicates an overall strong antiferromagnetic coupling confirmed by DFT calculations.     

Asymmetric chemoenzymatic synthesis of ramatroban using lipases and oxidoreductases

A chemoenzymatic asymmetric route for the preparation of enantiopure (R)-ramatroban has been developed for the first time. The action of lipases and oxidoreductases has been independently studied, and both were found as excellent biocatalysts for the production of adequate chiral intermediates under very mild reaction conditions. CAL-B efficiently catalyzed the resolution of (±)-2,3,4,9-tetrahydro-1H-carbazol-3-ol that was acylated with high stereocontrol. On the other hand, ADH-A mediated bioreduction of 4,9-dihydro-1H-carbazol-3(2H)-one provided an alternative access to the same enantiopure alcohol previously obtained through lipase-catalyzed resolution, a useful synthetic building block in the synthesis of ramatroban. Inversion of the absolute configuration of (S)-2,3,4,9-tetrahydro-1H-carbazol-3-ol has been identified as a key point in the synthetic route, optimizing this process to avoid racemization of the azide intermediate, finally yielding (R)-ramatroban in enantiopure form by the formation of the corresponding amine and the convenient functionalization of both exocyclic and indole nitrogen atoms.     

Copper-catalyzed dimerization of chromium Fischer carbene complexes: synthesis of dialkoxytrienes and their Nazarov-type cyclization to 2-alkoxy-2-cyclopentenones

Fischer carbene complexes 1 underwent a clean ligand dimerization reaction yielding functionalized olefins and trienes 4 in the presence of copper (I) catalysts. If treated with trifluoroacetic acid (TFA), trienes 4c, d, f undergo a cyclization process (Nazarov reaction) which furnishes cyclopentenone derivatives 6c, d, 7c, d and 8 in good yields. Finally, the Fischer aminocarbene 9 efficiently cyclodimerizes to the substituted arene 10 in the presence of CuBr.     

Development of a multi-residue method for the determination of organic micropollutants in water, sediment and mussels using gas chromatography-tandem mass spectrometry

This study describes the development of a multiresidue method based on gas chromatography-electron ionization-tandem mass spectrometry (GC-EI-MS/MS) for the detection of sixteen polycyclic aromatic hydrocarbons (PAHs), five phthalate esters (PEs), seven polychlorinated biphenyls (PCBs), six polybrominated diphenyl ethers (PBDEs), six alkylphenols (APs), three organochlorined pesticides and their isomers or degradation products (OCPs) and bisphenol A in seawater, river water, wastewater treatment plant (WWTP) effluents, sediments and mussels. Solid phase extraction (SPE) was used for the extraction of target analytes in aqueous samples, and ultrasound assisted extraction for solid samples. GC-EI-MS/MS acquisition conditions in selected reaction monitoring (SRM) using two transitions per compound were optimized. In this way, quantification and unequivocal identification of organic micropollutants were performed in compliance with the Decision 2002/657/EC. Good linearity responses with coefficients of determination higher than 0.99 were obtained. Methodological detection limits (MDLs) in seawater ranged from 0.1 to 6 ng L(-1); in river water from 0.1 to 4.8 ng L(-1); in WWTP effluents from 1 to 75 ng L(-1); in sediments from 1 to 150 ng g(-1) and in mussels from 1 to 125 ng g(-1). MDLs and recovery yields were compared with other published methods and similarities or even improvements were achieved. The optimized method was applied to analyze five samples from each matrix collected in coastal areas, showing its potential use for marine pollution monitoring.     

Recent advances in indole syntheses: new routes for a classic target

Indoles are the most abundant heterocycles in biologically active natural products, pharmaceuticals, agrochemicals, and are relevant substructures in functional materials. As a result, the development of methodologies that enable the synthesis of these compounds is continuously demanded. This review summarizes most recent and relevant approaches towards the preparation of this prevalent structural motif.     

Pentanuclear Ba(II) complex of a macrocyclic ligand

We report here the first pentanuclear Ba(II) complex of a new tri-aza, tri-oxa macrocycle with two carboxymethyl "arms" pending from two N atoms, H2L2. The crystal structure corresponds to the formula [Ba5(H0.375L2)4(ClO4)(CH3CH2OH)(H2O)2](ClO4)2.5 x 9.5H2O and reveals the presence of four molecules of the ligand surrounding five Ba(II) ions, giving rise to an unusual structure with the metal ions inside a spherical organic cavity.     

Pentafluorophenyl imidato palladium(II) complexes: catalysts for Suzuki cross-coupling reactions

Novel N-bonded imidato complexes of general formula [Pd(N-N)(C6F5)(imidate)](imidate = maleimidate, succinimidate or phthalimidate; N-N = 2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'-bipyridine (Me2bipy) or N,N,N',N'-tetramethylethylenediamine (tmeda)), [NBu4][Pd(C6F5)(H2O)(succinimidate)2] and [NBu4][Pd(C6F5)(L)(succinimidate)2](L = PPh3 or t-BuNC) have been synthesised. These complexes are air-, light- and moisture-stable. The crystal structures of [Pd(tmeda)(C6F5)(maleimidate)].H2O.0.5CHCl3, [NBu4][Pd(C6F5)(H2O)(succinimidate)2].H2O and [NBu4][Pd(C6F5)(t-BuNC)(succinimidate)2].2H2O have been determined by X-ray diffraction. Many of these new complexes are shown to be active phosphine-free palladium catalysts/precatalysts for the Suzuki cross-coupling reactions of aryl bromides and aryl chlorides with phenylboronic acid.     

Synthesis and Transformations of 5‐Chloro‐2,2′‐Dipyrrins and Their Boron Complexes, 8‐Chloro‐BODIPYs

Symmetric dipyrrylketones 1 a , b were synthesized in two steps from the corresponding α‐free pyrroles, by reaction with thiophosgene followed by oxidative hydrolysis under basic conditions. The dipyrrylketones produced the corresponding 5‐chloro‐dipyrrinium salts or 5‐ethoxy‐dipyrrins on reaction with phosgene or Meerwein’s salt, respectively. Boron complexation of the dipyrrins afforded the corresponding 8‐functionalized BODIPYs (borondipyrromethenes) in high yields. The 5‐chloro‐dipyrrinium salts reacted with methoxide or ethoxide ions to produce monopyrrole esters, presumably via a 5,5‐dialkoxy‐dipyrromethane intermediate. In contrast, 8‐chloro‐BODIPYs underwent a variety of nucleophilic substitutions of the chloro group in the presence of alkoxide ions, Grignard reagents, and thiols. In the presence of excess alkoxide or Grignard reagent, at room temperature or above, substitution at the boron center also occurred. The 8‐chloro‐BODIPY was a particularly useful reagent for the preparation of 8‐aryl‐, 8‐alkyl‐, and 8‐vinyl‐substituted BODIPYs in very high yields, using Pd⁰‐catalyzed Stille cross‐coupling reactions. The X‐ray structures of eleven BODIPYs and two pyrroles are presented, and the spectroscopic properties of the synthesized BODIPYs are discussed.     

Nickel Supported on Alkaline Earth Metal–Doped γ-Al2O3–La2O3 as Catalysts for Dry Reforming of Methane

Russian Journal of Applied Chemistry - Nickel catalysts supported on γ–Al2O3 doped with La2O3 and alkaline earth oxides (MgO, CaO, and SrO) were investigated in the dry reforming of...