Visible-light irradiation of 4-p-methoxyphenyl-3-butenylthioglucoside donors in the presence of Umemoto's reagent and alcohol acceptors serves as a mild approach to O-glycosylation. Visible-light photocatalysts are not required for activation, and alkyl- and arylthioglycosides not bearing the p-methoxystyrene are inert to these conditions. Experimental and computational evidence for an intervening electron donor-acceptor complex, which is necessary for reactivity, is provided. Yields with primary, secondary, and tertiary alcohol acceptors range from moderate to high. Complete β-selectivity can be attained through neighboring-group participation.

The reaction of a methanolic solution containing the bi-compartmental phenolic ligand 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenol (L(Cl)-OH) with MCl2·nH2O in the presence of NH4PF6 or NaClO4 afforded the dinuclear bridged-phenoxido dichlorido-metal(ii) complexes [Co2(μ-L(Cl)O)(H2O)2Cl2][Co2(μ-L(Cl)O)(MeOH)2Cl2](PF6)2 (), [Ni2(μ-L(Cl)O)(MeOH)2Cl2]PF6 (), [Ni2(μ-L(Cl)O)(MeOH)(H2O)Cl2]ClO4·1.25H2O (), [Cu2(μ-L(Cl)O)Cl2]PF6·1/2MeOH () and [Zn2(μ-L(Cl)O)Cl2]PF6·MeOH (). The complexes were characterized by elemental microanalyses, conductivity measurements, IR and UV-Vis spectroscopy, mass spectrometry and single crystal X-ray crystallography. Each M(ii) center within the dinuclear complex cations is octahedrally coordinated in complexes , and five-coordinated distorted square pyramidal in and . Magnetic susceptibility measurements at variable temperature of the complexes revealed weak to moderate antiferromagnetic coupling with |J| values = 8.38, 39.0, 30.2 and 0.79 cm(-1), respectively. The results of DFT calculations correlate well with the experimentally determined antiferromagnetic coupling and show that the magnetic exchange coupling occurs mainly through the phenoxido bridge M-O-M. Implications of geometry around the central metal ion, MM distance, M-O-M bond angle and overlapping of magnetic orbitals on the magnetic exchange coupling are discussed.

Mild conditions are reported for the hydroxylation of aliphatic C-H bonds through radical translocation, oxidation to carbocation, and nucleophilic trapping with H2O. This remote functionalization employs fac-[Ir(ppy)3] together with Tz(o) sulfonate esters and sulfonamides to facilitate the site-selective replacement of relatively inert C-H bonds with the more synthetically useful C-OH group. The hydroxylation of a range of substrates and the methoxylation of two substrates through 1,6- and 1,7-hydrogen-atom transfer are demonstrated. In addition, a synthesis of the antidepressant fluoxetine using remote hydroxylation as a key step is presented.

The nematode Caenorhabditis elegans secretes ascarosides, structurally diverse derivatives of the 3,6-dideoxysugar ascarylose, and uses them in chemical communication. At high population densities, specific ascarosides, which are together known as the dauer pheromone, trigger entry into the stress-resistant dauer larval stage. In order to study the structure-activity relationships for the ascarosides, we synthesized a panel of ascarosides and tested them for dauer-inducing activity. This panel includes a number of natural ascarosides that were detected in crude pheromone extract, but as yet have no assigned function, as well as many unnatural ascaroside derivatives. Most of these ascarosides, some of which have significant structural similarity to the natural dauer pheromone components, have very little dauer-inducing activity. Our results provide a primer to ascaroside structure-activity relationships and suggest that slight modifications to ascaroside structure dramatically influence binding to the relevant G protein-coupled receptors that control dauer formation.

Four new doubly bridged Cd(II)-azido complexes derived from sterically hindered NNN- and NN-donors were synthesized and structurally characterized. The tridentate amine ligands 2-methylquinolyl-2(ethyl-2-pyridyl)-methylamine (Meepmqa) and bis(2-methylypyridyl)methylamine (MeDPA) afforded the dinuclear complexes [Cd2(Meepmqa)2(μ1,3-N3)2(N3)2] (1) and [Cd2(MeDPA)2(μ1,1-N3)2(N3)2] (2) with di-EE- and di-EO-azido bridges, respectively. The N-substituted trialkyl ethylenediamine compounds N,N,N′-triethylethylenediamine (Et3en) and N,N,N′-trimethylethylenediamine (Me3en) resulted in the formation of 1D-polymeric chains {[Cd2(Et3en)2(μ1,1-N3)2(μ1,3-N3)2]} n (3) and {[Cd4(Me3en)4(μ1,1-N3)6(μ1,3-N3)2]} n (4) with alternative (di-EO/di-EE)- and di(EO/EO/EO/EE)-azido bonding modes. The IR asymmetric stretching vibration, νas(N3) of the azido ligands in these complexes and in related complexes, were analyzed in an attempt to predict the coordination bonding mode of the bridged azide. The fluorescence properties of the ligand Meepmqa and its complex 1 are reported. The Cd-complex 1 has increased fluorescence intensity compared to its free ligand. This was attributed to the strong Cd–N bond of the quinolyl group of Meepmqa and the nonflexibility of the corresponding five-membered chelate ring.

No abstract

No abstract

Five mono-nuclear Cu(II) and Ni(II) complexes and one dinuclear Zn(II) complex were synthesized from the Schiff bases N,N'-bis(3-ethoxy-2-hydroxybenzylidene)-1,2-phenylenediamine (H 2 L OEt -phda) and 2-ethoxy-6-({2- [(3-ethoxy-The complexes were structurally characterized with elemental microanalyses, IR, UV-Vis and ESI-MS spectroscopic techniques as well as single crystal X-ray crystallography. The metal centers display distorted square planar geometries in 2-4 and 5 and distorted square pyramidal (SP) in 1, whereas in 6 an intermediate geometry between SP and TBP was observed around the first Zn 2+ ion and a tetrahedral around the second ion, with one acetate is acting as a bridging ligand. In all cases, metal ions were incorporated into the N 2 -O 2 binding site with no involvement of the alkoxy groups in the coordination. The L OEt -ambza-complexes 3-6 revealed significant dihedral angles between the phenol rings and the plane containing the central benzene ring, and large O 2 -O 2 bond distances (5.1-5.9Ǻ). Results are discussed in relation to other related Schiff base complexes.