A comparative study of metal-catalyzed three-component synthesis of α-aminophosphonates

Different metal catalysts have been tested for the one-pot transformation of carbonyl compounds, amines and phosphites to α-aminophosphonates. The influence of catalyst type, amount, solvent and the substrate electronic factor have been investigated. The results revealed that the carbonyl compounds could be smoothly converted into α-aminophosphonates at room temperature in good to excellent yields, with or without solvent in a reasonable reaction time. These results suggested that among others, lithium perchlorate and metal triflates were proven to be effective catalysts in 10 moles % catalysts. Polar aprotic solvents proved to be the best for the synthesis of α-aminophosphonates. The synthesized compounds' structure characterizations were elucidated by different spectroscopic tools and showed results consistent with the expected structures.

Steric and electronic factor comparisons in hydrotris(3-phenylpyrazolyl)borate nickel(II) aryloxides

Hydrotris(pyrazolyl)borate (Tp) ligands, also known as scorpionates, are potent tridentate donors that effectively bind metal ions in a face-capping array. Hydrotris(3-phenylpyrazolyl)borate enforces a tetrahedral environment on NiIIto model metalloenzymes. The syntheses and structural characterizations of a number of [hydrotris(3-phenylpyrazolyl)borato]nickel(II) aryloxides were performed to provide insight into the environment of the model active site; these compounds are chlorido[hydrotris(3-phenylpyrazolyl-κN2)borato](3-phenyl-1H-pyrazole-κN2)nickel(II) chloroform monosolvate, [Ni(C27H22BN6)Cl(C9H8N2)]·CHCl3, (2), [hydrotris(3-phenylpyrazolyl-κN2)borato](phenolato-κO)nickel(II), [Ni(C27H22BN6)(C6H5O)], (3), (2,6-dimethylphenolato-κO)[hydrotris(3-phenylpyrazolyl-κN2)borato]nickel(II) [Ni(C27H22BN6)(C8H9O)], (4), (4-tert-butylphenolato-κO)[hydrotris(3-phenylpyrazolyl-κN2)borato]nickel(II), [Ni(C27H22BN6)(C10H13O)], (5), and [hydrotris(3-phenylpyrazolyl-κN2)borato](phenolato-κO)(tetrahydrofuran-κO)nickel(II) tetrahydrofuran monosolvate, [Ni(C27H22BN6)(C6H5O)(C4H8O)]·C4H8O, (6). Alkyl groups,e.g. tert-butyl in (5) and methyl in (4), electronically activate the aryloxide group to intramolecular π–π stacking but can be frustrated by steric encumbrance at the interacting ring faces. The flexibility at the nickel coordination site, afforded by the uncrowded B atom of the TpPhligand, allows tetrahydrofuran coordination in the phenolate compound.

Flipping of the coordinated triazine moiety in Cu(i)–L2and the small electronic factor, κel, for direct outer-sphere cross reactions: syntheses, crystal structures and redox behaviour of copper(ii)/(i)–L2complexes (L = 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)

Flipping of the triazine ring of the coordinated pdt ligand was observed, and the non-adiabaticity factorκelfor direct cross reactions was estimated asca.10−7.

Synthesis and Antibacterial Screening of Some 1-Aroyl-3-aryl Thiourea Derivatives

A series of 1-aroyl-3-aryl thioureas derivatives were synthesized and evaluated for antibacterial activity. The results indicated that the compounds possessed higher activity against gram-negative bacteria than gram-positive bacteria. Amongst all these compounds, C18 (89.4%) exhibited the greatest antibacterial activity against gram-negative bacteria while C5 (85.6%) displayed maximum antibacterial activity against gram-positive bacteria. Preliminary study of the structure-activity relationship revealed that an electronic factor on aryl rings had a great effect on the antibacterial activity of these compounds.