Thiophene 1-oxide Research Articles

Radiolytic degradation of thiophene: Performance, pathway and toxicity evaluation

Thiophene is one of typical refractory organic pollutants in coal chemical wastewater, which cannot be effectively removed by traditional biological treatment processes. In this study, ionizing radiation was used to degrade thiophene. The effect of absorbed dose, initial concentration and pH on the thiophene degradation was investigated. The results showed that thiophene could be completely degraded when the its initial concentration was 5 mg/L, the pH was 9, and the absorbed dose was 5 kGy. The results of quenching experiments indicated that all the hydroxyl radicals, hydrated electron and hydrogen radicals were responsible for the degradation of thiophene, which explained the wide range of pH application for the thiophene degradation by ionizing radiation. Four degradation intermediates were identified, including thiophene 1-oxide, thiophen-2-ol, 2,3-dihydrothiophen-2-ol and acetic acid, and two possible pathways of thiophene degradation were thus proposed. Ecological structure activity relationships program analysis suggested that thiophene 1-oxide and thiophen-2-ol were more toxic than thiophene. In general, ionizing radiation is an effective technology for thiophene degradation.

Origin of π-Facial Stereoselectivity in Thiophene 1-Oxide Cycloadditions.

We report a DFT computational study (M06-2X) of π-facial selectivity in the Diels-Alder reactions of thiophene 1-oxide. The preference for the syn cycloaddition arises because the ground state geometry of thiophene 1-oxide is predistorted into an envelope conformation that resembles the syn transition state geometry. The syn distortion occurs to minimize the effect of hyperconjugative antiaromaticity in the thiophene 1-oxide, arising from overlap of the σ*SO with the π-system. The syn selectivity follows through to the product structure that is stabilized by a π-σ*SO interaction, related to the 7-norbornenyl ion stability.

Thermally Stable Monosubstituted Thiophene 1-Oxide and 1-Imides Stabilized by a Bulky Rind Group at Their 3-Position: Synthesis, Structure, and Inversion Barriers on the Sulfur Atom

Abstract The synthesis and characterization of thermally stable monosubstituted thiophene 1-oxide and 1-imides stabilized by EMind (1,1,7,7-tetraethyl-3,3,5,5-tetramethyl-s-hydrindacen-4-yl) group on the 3-position are described. In addition to the molecular structures determined by X-ray crystallography, inversion barriers at the three-coordinated sulfur atoms have been determined by a coalescence method using diastereotopic C-3 and C-5 indacene carbon atoms as a 13C NMR probe.

Synthesis, Optical Properties, and Electronic Structures of Tetrakis(pentafluorophenyl)tetrathiaisophlorin Dioxide.

The synthesis, structure, optical and redox properties, and electronic structure of tetrakis(pentafluorophenyl)tetrathiaisophlorin dioxide (12) are reported. Oxidation of tetrakis(pentafluorophenyl)tetrathiaisophlorin (11) with dimethyldioxirane afforded the oxidized product, which was the tetrathiaisophlorin with two thiophene 1-oxide moieties (12). More significant nonplanarity and greater bond length alternation in 12 than those of 11 were observed by X-ray structural analysis. The absorption spectrum of 12 contains two bands at λ=348 and 276 nm, with a weak tail that extends to λ≈650 nm. Analysis of the magnetic circular dichroism spectrum of 12, based on Michl's 4N-perimeter model and molecular orbital calculations, indicate that the broad band at λ=348 nm appears to contain N2 and P2 bands, and 12 is classified as a 4nπ system, similar to 11. The nuclear-independent chemical shift values and (1) H NMR spectroscopy data indicate that 12 has more antiaromatic character than 11.

Determination of absolute configuration using ab initio calculation of optical rotation.

Ab initio Density Functional Theory (DFT) calculations of transparent spectral region, discrete frequency specific rotations were used to assign the absolute configurations (ACs) of: 1, 2H-naphtho[1,8-bc]thiophene 1-oxide; 2, m-F-phenyl glycidic acid methyl ester; 3, o-Br-phenyl glycidic acid methyl ester; 4, p-CH(3)-phenyl glycidic acid methyl ester; 5, 2-(1-hydroxyethyl)-chromen-4-one; and 6, 6-Br-2-(1-hydroxyethyl)-chromen-4-one. The ACs of 5 and 6 were previously determined via X-ray crystallography to be: 5, R(-)/S(+); 6, R(+)/S(-). The ACs obtained using [alpha](D) are the same for both 5 and 6: R(+)/S(-). We conclude that the previously reported AC of 5 is incorrect.

Determination of Absolute Configuration Using Optical Rotation Calculated Using Density Functional Theory

[structure: see text] We report the first determinations of the absolute configurations (ACs) of chiral molecules using discrete frequency, transparent spectral region optical rotations calculated using density functional theory (DFT). The ACs of 2H-naphtho[1,8-bc]thiophene 1-oxide (3), naphtho[1,8-cd]-1,2-dithiole 1-oxide (4), and 9-phenanthryl methyl sulfoxide (5) are determined by comparison of their specific rotations to values calculated via the time-dependent DFT/gauge-invariant atomic orbital (TDDFT/GIAO) methodology using the B3LYP functional and the aug-cc-pVDZ basis set.

Use of isotopes and LC-MS-ESI-TOF for mechanistic studies of tienilic acid metabolic activation.

Tienilic Acid (TA) is a uricosuric drug marketed in 1978 and which caused a number of rare immunoallergic hepatitis. It was withdrawn in US in 1980, in France in 1992. Early batches of tienilic acid also contained 0.1–0.5% tienilic acid isomer. Tienilic acid isomer (TAI), has been shown to be metabolised by Cytochrome P450 into a reactive thiophene 1-oxide which either binds to proteins, or can be trapped by sulfur nucleophiles (Valadon et al. 1996). Tienilic acid is metabolized by human cytochrome P450 2C9 into 5-hydroxytienilic acid (a major metabolite representing 70% of the dose excreted in human urine) but it also forms (a) reactive metabolite(s) which binds covalently to CYP 2C9 and it is a mechanism based inhibitor of CYP 2C9. Adding glutathione to incubations decreases the covalent binding, but only to 1 mol/mol P450. However the reactive metabolite of tienilic acid is still unknown. Recently Koenigs et al. have shown using ESI-LC-MS that CYP 2C9 binds ≈ 2 mol of TA in absence of GSH and only one in presence of 3 mM GSH (Koenigs et al. 1999).

Resolution and Chiroptical Characterization of Two 1,8-Bridged Naphthalene Systems: Naphtho[1,8-cd]-1,2-dithiole 1-Oxide and 2H-Naphtho[1,8-bc]thiophene 1-Oxide.

The enantiomers of the cyclic thiolsulfinate naphtho[1,8-cd]-1,2-dithiole 1-oxide, (+/-)-1, have been obtained by semipreparative chiral liquid chromatography of the racemate and characterized by c ...

Enantioselective dioxygenase-catalysed formation and thermal racemisation of chiral thiophene sulfoxides

Substituted chiral thiophene 1-oxides and their cycloadducts of variable enantiopurity have been isolated as products of dioxygenase-catalysed sulfoxidation of the corresponding thiophenes using intact cells of Pseudomonas putida; thermal racemization (ΔG‡= 25.1 kcal mol–1) of the enantiopure metabolite (1R)-2-methylbenzo[b]thiophene 1-oxide has been observed.

Base hydrolysis of ruthenium(II) thiophene complexes and reactions of the coordinated ligands

This paper describes the acid/base reactivity of a series of ruthenium thiophene complexes. In the acid form the starting compounds (ring)Ru(C[sub 4]R[sub 4]S)[sup 2+] are reactive toward 2 equiv of aqueous base, first as an OH- acceptor and next as a proton donor. The first and the second conjugate bases exist in at least two isomeric forms whose interconversions we have examined. The present results are related to previous work where we showed that one C-S bond in (C[sub 5]Me[sub 5])Rh(C[sub 4]R-4S)[sup 2+] undergoes base hydrolysis by attack of 2 equiv of OH-. C-S cleavage occurs upon deprotonation of the intermediate [(C[sub 5]Me[sub 5])-Rh([eta][sup 4]-C[sub 4]R-4S-2-OH)][sup +], giving rise to a neutral acyl thiolato complex. Furthermore NMR measurements indicated that the resulting acyl thiolates were dynamic in a manner that was poorly understood. We also showed that the initial attack of (excess) base results in formation of the thiophene 1-oxide complex [(C[sub 5]Me[sub 5])Rh([eta][sup 4]-C[sub 4]R[sub 4]S-1-O)], but intermediates in the formation of this S-oxide were not observed. Our studies of related ruthenium systems have uncovered the following: (i) evidence that S-hydroxythiophene complexes are precursors to the thiophene 1-oxides and C[sub 4]R[sub 4]S-2-OH complexes, (ii) an explanation of the dynamicmore » properties of the acyl thiolates, and (iii) the stereochemical course of the protonation of the acyl thiolates. 23 refs., 2 figs.« less