Thomas E. Glass

The effect of salt on selectivity in water soluble hydroformylation catalysts

Abstract The hydroformylation of octene-1 under two-phase reaction conditions with rhodium catalysts derived from TPPTS (trisulfonated triphenylphosphine) or the new water soluble phosphines, P[C6H4-p-(CH2)xC6H4-p-SO3Na]3, x = 3, 6, is salt concentration dependent. Both reaction rate and reaction selectivity are affected by the ionic strength of the aqueous reaction medium. Reaction selectivity increases with increased ionic strength while activity is dependent on whether the phosphine is capable of forming micelles. Reaction rate increases with increased ionic strength with the new surface active phosphines. The concentration of all components, free ligand, rhodium complex and salt affect the activation barrier to ligand exchange in HRh(CO)(TPPTS)3 as determined by dynamic 31P NMR spectroscopy. At low concentration with no added salt the barrier to exchange is estimated to be 22.4 kcal mol−1 whereas at high ligand and complex concentration the barrier is estimated to be 30.6 kcal mol−1. It is proposed that high ionic strength stabilizes the complex, HRh(CO)(TPPTS)3, in aqueous solution.

(S)-3,7-Dimethyl-2-oxo-6-octene-1,3-diol: an aggregation pheromone of the Colorado potato beetle, Leptinotarsa decemlineata (Say)

(S)-3,7-Dimethyl-2-oxo-6-octene-1,3-diol has been identified as a male-produced pheromone from the Colorado potato beetle. Its gross structure was deduced from its mass and NMR spectra plus synthesis from geraniol. The absolute configuration was determined to be (S) by syntheses of both enantiomers from (R)- and (S)-linalool, respectively.

Synthesis and characterization of the first trimetallic nitride templated pyrrolidino endohedral metallofullerenes

New pyrrolidino derivatives of both diamagnetic and paramagnetic trimetallic nitride templated endohedral metallofullerenes were synthesized by the Prato reaction, isolated and characterized by means of MALDI-TOF MS, NMR and UV-vis spectroscopies.

Pentaoxygenated xanthones from Bredemeyera floribunda

A chloroform extract of the roots of Bredemeyera floribunda yielded two new pentaoxygenated xanthones, 1,7-dihydroxy-3,4,8-trimethoxyxanthone and 1,3,7-trihydroxy-4,8-dimethoxyxanthone, and the ethanol extract of the resulting marc yielded 1,3,6-trihydroxy-2,7-dimethoxyxanthone. Structure determination of these pentaoxygenated xanthones was accomplished by spectral analysis, mainly NMR, including normal and inverse detection techniques such as HETCOR and HMBC. Chemical derivatization and comparison to literature data were also used.

NMR Studies of Sol-Gel Derived Hybrid Materials Based on Triethoxysilylated Diethylenetriamine and Tetramethoxysilane

Inorganic-organic hybrid materials were prepared by hydrolysis and condensation of triethoxysilylated diethylenetriamine (f-DETA) and tetramethoxysilane (TMOS). The prehydrolysis stage of this f-DETA/TMOS system was monitored by 29Si NMR spectroscopy. The NMR experiments indicated that f-DETA hydrolyzes and condenses nearly as fast as TMOS at pH 0–1, but lags far behind the latter at pH~4.2. Gels derived from f-DETA and TMOS were studied using 13C or 29Si solid state NMR spectroscopy. The concentration of the alkoxy groups and the extent of condensation of the T & Q species in the cured gels were estimated. The contents of the Si–OMe group and Si–OEt group were barely detectable in most water-abundant systems (equivalent ratio of water to alkoxysilane ~4.0). However, a significant amount of Si–OiPr groups was found if the reactant f-DETA was stored at room temperature in solvent 2-propanol for three weeks or longer. The relative composition of each Tz or Qz species was estimated for gels prepared in media of different acidity levels and water concentrations and then cured at 125–130°C for 4 h. As the acidity of the medium increased from pH 0–2 to pH 4–5, the extent of condensation of the T species decreased but that of the Q species increased. The hydrolysis of urea groups in f-DETA during the sol-gel process was also evaluated by 13C solid state NMR spectroscopy. The results indicated that only a very small fraction of urea groups was hydrolyzed during the sol-gel process.

Furofuranonaphthoquinones: bioactive compounds with a novel fused ring system from crescentia cujete

Abstract Bioassay-directed fractionation of the methyl ethyl ketone extract of Crescentia cujete yielded the naphthoquinones 1 and 2. Both compounds are cytotoxic, and 1 shows selective DNA-damaging activity against yeast. Detailed spectroscopic interpretation led to the assignment of the structures of 1 and 2 as 3-hydroxymethylfuro[3,2-b]naphtho[2,3-d]furan-5,10-dione and 9-hydroxy-3-hydroxymethylfuro[3,2-b]naphtho[2,3-d]furan-5,10-dione, respectively. This is the first report of this fused furofuran ring system, either as a natural product or a synthetic substance.

Phosphorus-31 NMR spin lattice relaxation times as an indirect probe of adsorbed water in supported aqueous phase catalysts

Abstract Phosphorus-31 spin lattice relaxation times, T1s, for SAP hydroformylation catalysts derived from HRh (CO) (TPPTS)3 and TPPTS (TPPTS = trisulfonated triphenyl phosphine trisodium salt) are consistent with a liquid-like character for the supported aqueous phase. Ale T1 for solid TPPTS is 1150 s while for TPPTS in a supported aqueous phase T1 varies from 220 to 4.9 s. A T1 of 4.9 s is close to the value obtained for TPPTS in solution and is observed at a H2O/P ratio of 24.9. At this level of water content previously reported SAP catalysts have shown maximum catalytic activity for the hydroformylation of olefins.

Reactivity of Isopropanol On H-Zsm-5 By in Situ, Flow Nmr MOnitoring

Abstract The first use of flow NMR for the study of heterogeneous reactions is reported. A NMR flow cell packed with H-ZSM-5 acts as a fixed bed reactor. Continuous flow of 13 C enriched isopropanol vapor diluted 1n N 2 or Xe is contacted with the catalyst at temperatures from 100–180°C. Reaction products are collected and analyzed. 13 C and 129 Xe NMR monitoring of the reaction zone is accomplished with a JEOL FX200 spectrometer. Acid catalyzed dehydration of isopropanol is observed at temperatures above 100°C.

Analysis of Middle Distillate Fuels by Flow Liquid Chromatography/Proton Nuclear Magnetic Resonance

Normal phase liquid chromatography (LC) is an appropriate technique for separating middle distillate fuels — jet and diesel — into major hydrocarbon classes. The use of a proton nuclear magnetic resonance (1H NMR) instrument as a continuous flow LC detector, in conjunction with a halocarbon liquid phase, generates a proton spectrum for each separated fraction in the sample. Specific proton types are measured via appropriate integration windows for each hydrocarbon class. A detailed set of equations allows the integration data to be interpreted as an average molecular composition for each chromatographic fraction. The treatment is particularly useful with the mono- and di-aromatic fractions.

Empirical and molecular modeling study of the pyridinium species RHPP+, an abundant and potentially neurotoxic metabolite of haloperidol

The “reduced” haloperidol pyridinium metabolite (RHPP+) is found in the brain, plasma and urine of patients treated with the neuroleptic drug haloperidol (HP). RHPP+ is suspected to be neurotoxic through a mechanism that entails interference with the mitochondrial electron transport chain. We have studied the conformation of this flexible molecule in solution (using NMR) and in the solid state by single crystal X-ray analysis. Using the solid state structure as initial input, molecular dynamics runs indicated that the molecule preferably exists in an unfolded, rather than a folded conformation. We propose that the interaction of RHPP+ with complexes in the mitochondrial respiratory chain is stabilized primarily by an ionic bond involving the cationic nitrogen and secondarily by hydrogen-bond anchoring originating from the hydroxy group. A comparison with HPP+, the “unreduced” pyridinium metabolite of HP, suggests that this latter interaction may—among other considerations such as lipophilicity—account for differences in the in vitro toxicological profiles of RHPP+ and HPP+, which carries a ketone group in lieu of the hydroxy.