Double template effect in [4 + 4] Schiff base macrocycle formation; an ESI-MS study

The mechanism of self-assembly of a polynuclear complex of a [4 + 4] Schiff base iminomethylenediphenolate macrocycle [BaCu(4)(4 + 4)](2+) via a non-macrocyclic dialdehyde intermediate has been followed using ESI-MS of the reaction solutions. Both assembly of the intermediate and Schiff-base condensation with diamine give rise to single products; formation of the intermediate metallacycle is fast but Schiff-base condensation is much slower. Both intermediate complex and macrocyclic product have been structurally characterised.     

Specificity in template syntheses of hexaaza-macrobicyclic cages: [Pt(Me5-tricosatrieneN6)]4+ and [Pt(Me5-tricosaneN6)]4+

The racemic C3 hexadentate cage complex, [Pt(Me5-tricosatrieneN6)]Cl4 (1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosa- 3,14,18-triene)platinum(IV) tetrachloride), was synthesised stereospecifically and regiospecifically from a reaction of the bis-triamine template [Pt(tamc)2]Cl4 (bis[1,1,1-tris(aminomethyl)ethane]- platinum(IV) tetrachloride) with formaldehyde and then propanal, in acetonitrile under basic conditions. Largely, one racemic diastereoisomer was obtained in a surprisingly high yield (approximately 50%), even though the molecule has seven chiral centres. The origins of the stereoselective synthesis are addressed. The crystal structure of [Pt(Me5-tricosatrieneN6)]-(ZnCl4)1.5Cl.2H2O showed that all three imines were attached to one tame fragment with a chiral amine site ([symbol: see text] SSS, delta RRR) and a chiral methine carbon site ([symbol: see text] RRR, delta SSS) on each ligand strand. The PtN6(4+) moiety had a slightly distorted octahedral configuration with the two types of Pt-N bonds related to the imine and the amine donors, 2.050(7) and 2.072(6) A, respectively. Treatment with sodium borohydride (15 s, 20 degrees C) at pH approximately 12.5 reduced the imine groups, but not the Pt(IV) ion, producing a C3 saturated ligand complex [Pt(Me5-tricosaneN6)]Cl4 ((1,5,9,13,20- pentamethyl-3,7,11,15,18,22- hexaazabicyclo[7.7.7]tricosane)platinum(IV)tetrachloride). X-ray crystallographic analysis showed that the average Pt-N bond distance in the cation increased upon imine reduction to 2.10 (av) A. The cyclic voltammograms of the two cage complexes displayed irreversible two-electron reduction waves in aqueous media and a approximately 0.3 V shift to more positive potentials compared to that of the smaller cavity sar (3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) analogue. After reduction, net dissociation of one strand of the cage was also evident, to give unstable square planar Pt(II) macrocyclic products.     

Novel bis-betaines and betaines within [1(4)]meta-heterophane frameworks

After prior selection of betaine building blocks for the construction of quadrupolar heterophane frameworks, a convergent "3+1" synthetic strategy is reported for the synthesis of the title macrocycles composed of heterocyclic betaine subunit(s). These typify the first example of simple cyclophanes constructed out of both highly pi-excessive and highly pi-deficient heteroaromatic moieties linked in a 1,3-alternating fashion. The chemical reactivity of the quadrupolar heterophanes 1a and 1c toward electrophiles under neutral conditions corroborated their bis-betaine structure. The structural features of the bis-betaines 1, betaines 2 x PF6 and 5 x X, and the corresponding dicationic [1(4)]heterophanes 3 x 2X and 4 x 2Cl were studied by 1H and 13C NMR spectroscopy and electrospray ionization mass spectrometry, and confirmed by single-crystal X-ray diffraction analysis of macrocycles 1a and 2a x PF6.     

Determination of the oximes 2-hydroxyiminomethyl-3-methyl-1-[2-(3-methyl- 3-nitrobutyloxymethyl)]imidazolium chloride and 1-[1-(3-butynyloxymethyl)]-2-hydroxyiminomethyl-3-methylimida zolium chloride in plasma by high-performance liquid chromatography

An assay is presented for the extraction and quantitation of two oximes, 2-hydroxyimino-methyl-3-methyl-1-[2-(3-methyl-3-nitrobutyloxyme thyl)] imidazolium chloride (oxime A) and 1-[1-(3-butynyloxymethyl)]-2-hydroxyiminomethyl-3-methylimidazo lium chloride (oxime B), in human plasma and is demonstrated to be linear over two overlapping concentration ranges: 10-500 and 100-1000 ng/ml. The assay utilizes a liquid-liquid, ion-pair extraction and a normal-phase chromatographic separation on a silica column with ultraviolet detection at 270 nm. The method is sensitive, rapid and accurate. The limit of detection is 10 ng/ml (signal-to-noise ratio S/N greater than 10). The mean extraction recoveries of the oximes were greater than 86% at all concentration levels. The intra-assay variability was less than 3.3%, the inter-assay variability less than 7.2%. The compound is stable in plasma for 23 weeks when stored at -15 degrees C or -80 degrees C.     

Synthesis and properties of new (μ-oxo)bis[trichloroferrate(III)] dianion salts incorporated with dicationic moiety

New (μ-oxo)bis[trichloroferrate(III)] dianions-based ionic compounds that contain various counterdications were synthesized and characterized with regards to their crystal structures, thermal properties, and magnetic susceptibility. These salts are soluble in polar solvents such as methanol and water. The melting point of these compounds is affected by the dication following the order of triphenylphosphinium > pyridinium > imidazolium dications, and symmetrical dicationic salts > unsymmetrical ones. In these compounds, the trichloroferrate dianion exists in either a linear or a bent form, which is affected by the dications. Interestingly, the dicationic diferrate compounds show magnetic coupling constants fairly smaller than those reported in literature for diferrate salts in which monocations are the counterion. Furthermore, unlike the diferrate salts associated with separate monocations, the linear diferrate dicationic compounds show magnetic coupling constant lower than that of bent diferrate dicationic salts.     

Solvent effect on the complex formation of distally dialkylated calix[4]arenes with 1-chloro-4-(trifluoromethyl)benzene

The complexation behavior of the distally dialkylated calix[4]arenes and 4-tert-butylcalix[4]arenes (hosts) with 1-chloro-4-(trifluoromethyl)benzene (guest) was examined in four different alcohols (MeOH, EtOH, n-PrOH, n-BuOH) as solvents. The complex stability constants (K_s) and the complexation energy of the host-guest complexes were determined. Fair ‘by group’ linear correlations between each log K series determined in the same solvent and the complex stabilization energies were found. As a consequence, the solvents having high permittivities result in less stability of the host-guest complex in these particular cases examined.     

Bromthionitren-tetrabromo-wolfram, [WBr4(NSBr)]2

Bromothionitrene-tetrabromo-tungsten, [WBr₄(NSBr)]₂ [WBr₄(NSBr)]₂ is prepared by the reaction of the corresponding chlorothionitrene complex [WCl₄(NSCl)]₂ with excess trimethylsilylbromide. Unpure [WCl₄(NSBr)]₂ was also prepared. According to the i.r. spectra the bromothionitrene complexes are similar to the chlorothionitrene complex [WCl₄(NSCl)]₂, which was characterized earlier by X-ray methods. [MoCl₄(NSCl)]₂ reacts with Me₃SiBr forming MoNBr₃.     

Generation and detection of tellurane [10-Te-4(C4)] and selenurane [10-Se-4(C4)] having alkyl and aryl ligands

Formation of 2,2′-biphenylylenedimethylselenurane and -tellurane was observed by the ¹H, ¹³C, ⁷⁷Se, and ¹²⁵Te NMR studies at low temperature, in the reactions of dibenzoselenophene Se-oxide and 2,2′-biphenylylenedibromotellurane with methyllithium. These hypervalent compounds were unstable and decomposed at room temperature to give the corresponding dibenzochalcogenophenes quantitatively.     

1-(4-叔丁基苯基)-1,1-二[4-(4-硝基苯氧基)\]苯基乙烷的合成及其溶解性研究

以叔丁基苯为起始原料,经3步反应制得了一种新化合物1-(4-叔丁基苯基)-1,1-二[4-(4-硝基苯氧基)]苯基乙烷（3）,总收率61.14%,其结构经¹H NMR和IR表征。3可溶于非极性溶剂（石油醚除外）和极性非质子溶剂。     

Synthese und Kristallstruktur der Molybdännitrido‐Komplexe [MoNCl3(MeCN)]4 und [MoNCl2(bipy)]4

Syntheses and Crystal Structures of the Nitrido Complexes [MoNCl₃(MeCN)]₄ and [MoNCl₂(bipy)]₄ [MoNCl₃(MeCN)]₄ ( 1 ) is obtained by the reaction of MoCl₄(MeCN)₂ with Me₃SiN₃ in CH₂Cl₂ as a sparingly soluble and water sensitive red compound. It crystallizes as 1 · 3 CH₂Cl₂ in the triclinic space group P 1 with a = 889.7(1), b = 1004.8(1), c = 1270.4(2) pm; α = 71.69(1)°; β = 73.63(1)°; γ = 86.32(1)°, and Z = 1. It forms centrosymmetric tetranuclear complexes, in which the Mo atoms are connected by asymmetric and linear nitrido bridges with distances Mo–N of 167.5 and 214.3 pm. The acetonitrile molecules are coordinated with a long bond length Mo–N of 241 pm in trans position to the Mo–N triple bond. The reaction of 1 with 2,2′‐bipyridine in CH₂Cl₂/THF yields the tetranuclear molybdenum(V) complex [MoNCl₂(bipy)]₄ ( 2 ) as main product. It crystallizes in the tetragonal space group P4₂/n with a = 1637.5(2), c = 1018.3(2) pm, and Z = 2. In the tetranuclear complexes with the symmetry S₄ linear and asymmetric nitrido bridges connect the Mo atoms to form an almost planar eight membered Mo–N ring with distances Mo–N of 173 and 203 pm. The bipyridine molecules coordinate as chelates in cis and trans position to the Mo–N triple bond. In this case the trans influence causes different Mo–N distances of 219 and 232 pm.     

One-pot synthesis of 7-bromo-1-[4-(1-cyano-1-methylethyl)]-phenyl-[1,2,4]-triazole-[4,3-a]-quinoxalin

[1,2,4]-Triazole-[4,3-a]-quinoxaline is an important component of many drugs. The yield of the reported methods for triazole cyclization step was usually as low as 20%. In this article, the triazole cyclization step was successfully done by using microwave method with a high yield of 75% for the first time.