Carbyne-fluoro complexes of rhenium. Single-pot synthesis of trans-[ReF(CCH2R)-(Ph2PCH2CH2PPh2)2][BF4]

Treatment of a THF solution of trans-[ReCl(N₂)(dppe)₂] (dppe = Ph₂PCH₂CH₂PPh₂) with a 1-alkyne HCCR (R =^tBu, CO₂Me, CO₂Et, or C₆H₄Me-4), in the presence of Tl[BF₄]/[NH₄][BF₄], under sunlight, affords the corresponding carbyne-fluoro complexes trans-[ReF(CCH₂R)(dppe)₂][BF₄] in an unprecedented single-pot synthesis. Further reaction with [BU₄N]OH leads to the vinylidenefluoro compounds trans-[ReF(=C=CHR)(dppe)₂] (R = CO₂Me, CO₂Et, or C₆H₄Me-4).     

Synthesis and Diels-Alder reaction of a sapphyrin derivative

Sapphyrins participate in Diels-Alder reactions with pentacene affording novel barrelene-fused sapphyrins. The new compounds were synthesized using traditional heating and microwave irradiation conditions. The experiments carried out under microwave irradiation proved cleaner, affording only the monoadduct and in higher yields.     

Kalman filtering of data from first- and second-order kinetics

The Kalman filter algorithm was used to process data obtained in the simultaneous determination of species following first- and second-order kinetics. The performance of the algorithm in the quantification of chemical components from simulated data was assessed, and the influence of various parameters involved was estimated. The algorithm was applied to the resolution of cysteine-ascorbic acid and glutathione-ascorbic acid mixtures where the ascorbic acid followed pseudo first-order kinetics and the amino acids second-order kinetics in the reaction with the copper(II)-neocuproine system. Some features of the determinations (namely, afforded concentration ratios, accuracy and precision) are discussed.     

Solvent dependent conformational isomerism and ligand oxidation of novel Ru(II) cyclen complexes

The synthesis of cis-[Ru(II)(cyclen)(L)(x)](n+) (cyclen = 1,4,7,10-tetraazacyclododecane and L = 2,2'-bipyridine (bpy), phenanthroline (phen) or 4-cyanopyridinium (4-NCpyH(+))) is reported. The freshly prepared complexes are stable in aprotic solvents and cyclen undergoes oxidative dehydrogenation reaction at high pH. These compounds also present solvent dependent conformational isomerization.     

Determination of diclofensine, an antidepressant agent, and its major metabolites in human plasma by high-performance liquid chromatography with fluorometric detection

A sensitive and selective high-performance liquid chromatographic assay was developed for the determination of diclofensine (I) and its key metabolites in human plasma. The assay involves deproteinization of plasma, overnight Glusulase incubation to hydrolyze the major metabolite (I-B-glucuronide), extraction of the parent compound and its deconjugated metabolites (I-A, I-B and I-C) from the alkalinized aqueous phase into diethyl ether-ethanol (95:5), the residue of which (containing compounds I, I-A, I-B and I-C) is alkylated with 2-iodopropane dissolved in acetone, using solid potassium hydroxide as a catalyst. The compounds are extracted from the reaction mixture into diethyl ether, after adding ethanol-water-acetic acid (55:40:5), the residue of which is dissolved in 0.05 M sulfuric acid, and reacted with mercuric acetate at 100 degrees C, which oxidizes tertiary tetrahydroisoquinolines to their 3,4-dihydroisoquinoline derivatives, followed by a photochemical reaction in the same solution to form intensely fluorescent isoquinolinium derivatives. An aliquot of this reaction mixture is injected onto a reversed-phase high-performance liquid chromatography column (5-microns Nova-Pac C13 phase in a radial compression cartridge, 10 cm X 8 mm), using the mobile phase 0.25 M triethylammonium phosphate (pH 2.5)-0.25 M acetic acid-methanol-acetonitrile-tetrahydrofuran (150:350:125:375:25). The void volume (Vo) is approximately 1.4 min and the retention times (tR) of the respective isoquinolium derivatives of diclofensine (I) are ca. 3.5 min, internal standard (II) ca. 4.2 min, nordiclofensine (I-A) ca. 5 min, while the phenolic metabolites I-B and I-C give peaks at 6.4 min and 10.4 min, respectively. The derivatives are detected by fluorescence. The method was used to determine plasma concentrations of the parent drug (I) and its major phenolic metabolite I-B (aglycone) in plasma in two normal volunteers following a single oral 45-mg dose and following seven consecutive days of oral dosing of 45 mg three times a day as part of a multiple ascending dose tolerance study.     

Reactivity of 2-halo-2H-azirines. 1. Reactions with nucleophiles.

Nucleophilic substitution reactions of 2-halo-2H-azirines 1a, 1b, 1d, and 1e with potassium phthalimide and aniline allowed the preparation of new substituted 2H-azirines 2-5. The reactions of 2-bromo-2H-azirine 1a with methylamine led to the synthesis of alpha-diimines 7 and 8. 2-Halo-2H-azirines were also established as building blocks for the synthesis of a range of heterocyclic compounds, namely, quinoxalines 10a-10d, 3-oxazoline 14, and 2H-[1,4]oxazines 18 and 20. X-ray crystal structures of alpha-diimine 7, 3-oxazoline 14, and 2H-[1,4]oxazine 18 are reported.     

Two-step upflow anaerobic sludge bed system for sewage treatment under subtropical conditions with posttreatment in waste stabilization ponds

A pilot-scale sewage treatment system consisting of two upflow anaerobic sludge bed (UASB) reactors followed by five waste stabilization ponds (WSPs) in series was studied under subtropical conditions. The first UASB reactor started up in only 1 mo (stable operation, high chemical oxygen demand [COD] removal efficiency, low volatile fatty acids concentration in the effluent, alkalinity ratio above 0.7, biogas production above 0.1 Nm3/kg of CODremoved). Removal efficiencies up to 90% were obtained in the anaerobic steps at a hydraulic retention time of 6 + 4 h (80% removal in the first step). Fecal coliform removal in the whole system was 99.9999% (99.94% in anaerobic steps and 99.98% in WSPs). COD balances over UASB reactors are provided. A minimum set of data necessary to build COD balances is proposed. Intermittent sludge washout was detected in the reactors with the COD balances. Sludge washout from single-step UASB reactors should be monitored and minimized in order to ensure constant compliance with discharge standards, especially when no posttreatment is provided. The system combined high COD and fecal coliform removal efficiency with an extremely low effluent concentration, complying with discharge standards, and making it an attractive option for sewage treatment in subtropical regions.     

Maximizing the xylitol production from sugar cane bagasse hydrolysate by controlling the aeration rate

Batch fermentations of sugar cane bagasse hemicellulosic hydrolysate treated for removing the inhibitors of the fermentation were performed byCandida guilliermondii FTI20037 for xylitol production. The fermentative parameters agitation and aeration rate were studied aiming the maximization of xylitol production from this agroindustrial residue. The maximal xylitol volumetric productivity (0.87 g/L h) and yield (0.67 g/g) were attained at 400/min and 0.45 v.v.m. (K_La 27/h). According to the results, a suitable control of the oxygen input permitting the xylitol formation from sugar cane bagasse hydrolysate is required for the development of an efficient fermentation process for large-scale applications.