Thioanisole Research Articles

Catching an Oxo Vanadate Porous Acetylacetonate Covalent Adaptive Catalytic Network that Renders Mustard-Gas Simulant Harmless.

In this work, we illustrated the design and development of a metal-coordinated porous organic polymer (POP) namely VO@TPA-POP via a post-synthetic metalation strategy to incorporate oxo-vanadium sites in a pristine polymer (TPA-POP) having acetylacetonate (acac) as anchoring moiety. The as-synthesized VO@TPA-POP exhibited highly robust and porous framework, which has been utilized for thioanisole (TA) oxidation to its corresponding sulfoxide. The catalyst demonstrated notable stability and recyclability by maintaining its catalytic activity over multiple reaction cycles without any significant loss in activity. The X-ray absorption spectroscopy (XAS) and density functional theory (DFT) analysis establish the existence of V(+4) oxidation state along with the VO(O)4 active sites into the porous network and the most energetically feasible mechanistic pathway involved in the TA oxidation, respectively, indicating the role of electron density associated with vanadium center during the catalytic transformation. Thus, this work aims at the demonstration of versatility and potential of VO@TPA-POP as a porous heterogeneous catalyst for the TA oxidation followed by decontamination of sulfur mustards (HD's) to their corresponding less toxic sulfoxides in a more efficient and greener way.

Ferrocene-derived Fe-metalated porous organic polymer for the core planarity-triggered detoxification of chemical warfare agents.

Herein, we demonstrate the successful construction of two Fe-metalated porous organic polymers having planar (Fe-Tt-POP) and non-planar (Fe-Rb-POP) geometry via the ternary copolymerization strategy for the catalytic oxidative decontamination of different sulfur-based mustard gas simulants (HD). Fe-Tt-POP exhibits superior catalytic performance for the oxidation of thioanisole (TA) in comparison with Fe-Rb-POP. Interestingly, this activity difference can be further explored by in situ operando DRIFTS and DFT computational studies.

Conformation-Specific Raman Bands and Electronic Conjugation in Substituted Thioanisoles

Nonresonant Raman spectra and conformational stability are studied for thioanisole (TA) and substituted analogues [4-XTA, X = NO(2) (1), CN (2), H (3), CH(3) (4), and NH(2) (5)] at the 4-position. The ring-substituent (SCH(3)) vibrational modes of out-of-plane bending and torsional types are calculated to have strong Raman scattering activities only for the vertical conformers. Agreement between observed and calculated Raman spectra is analyzed numerically. The conformational stability of the SCH(3) rotation changes systematically to the electron-withdrawing character of the substituents. The rotational barrier is calculated satisfactorily by B3LYP/6-31++G(d,p) calculations, whereas the second- to fourth-order Møller-Presset perturbation theory and coupled-cluster with single- and double-excitation calculations tend to overestimate conformational energy barriers with respect to coplanar forms. The coplanar form is obtained for 1 and 2, whereas the vertical conformer is favorable for 4 and 5. The origin of the conformational energy difference, DeltaE, is demonstrated on the basis of canonical molecular orbitals and natural bond orbitals (NBOs) of the ground state. The natural bond orbital interaction between a nonbonding n(S) orbital of the S atom and a pi orbital of the benzene ring is shown to stabilize the coplanar form predominantly. A linear relationship is obtained between the energy of the highest occupied molecular orbitals and DeltaE. The n(S)-pi interaction energy, E(2), based on the NBO representation and the Hammet constants also change linearly with respect to DeltaE.

Liquid phase acetylation of thioanisole with acetic anhydride to 4-(methylthio) acetophenone (4-MTAP) using H-beta catalyst

Acetylation of thioanisole (TA) with acetic anhydride (AA) to give p-(methylthio) acetophenone (4-MTAP) has been investigated using different solid acid catalysts such as H-Y, H-ZSM-5, H-mordenite and H-beta in liquid phase conditions. The reaction is studied in the temperature range 80–180 °C in a pressure reactor under nitrogen atmosphere. Among the catalysts tested, H-beta is found to be more active and shape selective than other zeolite catalysts. The conversion of TA (32 mol%) with a turnover frequency, TOF, 30.6 (10 −4 s −1 mol −1 Al) gave exclusively 4-MTAP (99.9%) and the other o-(methylthio) acetophenone (2-MTAP) over H-beta at 150 °C after 2 h. Acidity and structural features of zeolites play an important role in the conversion and product distribution in acetylation of TA. The effect of AA/TA molar ratio, catalyst concentration and reaction temperature have been optimized to get higher conversion of TA and product selectivity. Efficient utility of AA has been established in the reaction. H-beta catalyst has been reused in few cycles after regeneration by washing with ethyl acetate followed by calcination at 500 °C for 4 h without loss in its activity.

The rational design of semisynthetic peroxidases.

A semisynthetic peroxidase was designed by exploiting the structural similarity of the active sites of vanadium dependent haloperoxidases and acid phosphatases. Incorporation of vanadate ion into the active site of phytase (E.C. 3.1.3.8), which mediates in vivo the hydrolysis of phosphate esters, leads to the formation of a semisynthetic peroxidase, which catalyzes the enantioselective oxidation of prochiral sulfides with H(2)O(2) affording the S-sulfoxide, e.g. in 66% ee at 100% conversion for thioanisole. Under reaction conditions the semi-synthetic vanadium peroxidase is stable for over 3 days with only a slight decrease in turnover frequency. Polar water-miscible cosolvents, such as methanol, dioxane, and dimethoxyethane, can be used in concentrations of 30% (v/v) at a small penalty in activity and enantioselectivity. Among the transition metal oxoanions that are known to be potent inhibitors, only vanadate resulted in a semisynthetic peroxidase when incorporated into phytase. A number of other acid phosphatases and hydrolases were tested for peroxidase activity, when incorporated with vanadate ion. Phytases from Aspergillus ficuum, A. fumigatus, and A. nidulans, sulfatase from Helix pomatia, and phospholipase D from cabbage catalyzed enantioselective oxygen transfer reactions when incorporated with vanadium. However, phytase from A. ficuum was unique in also catalyzing the enantioselective sulfoxidation, albeit at a lower rate, in the absence of vanadate ion.

Photoinduced hydrogen- and electron-transfer processes between chloranil and aryl alkyl sulfides in organic solvents. Steady-state and time-resolved studies

The photochemical behavior of three aryl alkyl sulfides, thioanisole (TA), benzyl phenyl sulfide (BPS) and 4-methoxybenzyl phenyl sulfide (MBPS), sensitized by triplet chloranil (CA), was investigated by nanosecond laser flash photolysis and steady-state irradiation in CH2Cl2 and MeCN. The nature of the transients detected upon 355-nm laser excitation was independent of the molecular structure of the aryl alkyl sulfides but strongly affected by the solvent polarity. In particular, in CH2Cl2 the quenching process of triplet CA by aryl alkyl sulfides was accompanied by H-transfer, with formation of the CAH• and TA(-H)•/BPS(-H)•/MBPS(-H)• radicals. In contrast, a charge transfer process between triplet CA and aryl alkyl sulfides, with formation of the radical anion CA•− and radical cations of aryl alkyl sulfides, occurred in MeCN. In this solvent, a transient detected at long delay time was tentatively assigned to the anion CAH− formed by H-transfer between radical ions. In all experiments, transient species were characterized in terms of second-order decay rate constants and quantum yields of formation. Steady-state irradiation of the CA/TA system led to the stable photoadduct C6H5SCH2OC6Cl4OH in both CH2Cl2 and MeCN with quantum yields of 0.033 and 0.27, respectively. In contrast, aldehydes, thioacetals, and disulfides were the main products obtained upon irradiation of the CA/BPS and CA/MBPS systems. The photoaddition products were not observed, probably owing to their low stability. The nature of the photoproducts formed by irradiation of CA/aryl alkyl sulfides was independent of solvent properties, even though the reactivity was higher in MeCN than in CH2Cl2 .

Spectral, Kinetic, and Redox Studies on the Transients Formed on Reaction of Hydroxyl Radicals with Thioanisole

The hydroxyl radicals are observed to react with thioanisole (TA) with a bimolecular rate constant of 3.5 × 109 dm3 mol-1 s-1 and form transient optical absorption bands with λmax = 310, 365, 530, and 740 nm. The transient absorption bands at 310, 530, and 740 nm are also formed on reaction of specific one-electron oxidants such as CCl3OO•, Br2•-, and Cl2•- with thioanisole and are assigned to solute radical cations with positive charge on the benzene ring. Based on the studies with specific one-electron oxidants, ≈73% of •OH radicals are inferred to react with thioanisole by electron transfer and 27% by OH-adduct formation. The oxidation potential for the TA/TA•+ couple, based on the equilibrium established with the Br2•- / 2Br- couple, is determined to be 1.53 V vs NHE. The OH-adduct (λmax = 365 nm) is observed to undergo acid-catalyzed dehydration and form a solute radical cation. A small fraction of it is converted to sulfur-centered dimer radical cations and the major fraction into the monomer radical cations with the positive charge on the benzene ring. The monomer radical cations, formed in neutral aqueous solutions, are a strong one-electron oxidant and are able to oxidize I- with a bimolecular rate constant value of 6.4 × 109 dm3 mol-1 s-1.

Effect of substituent groups of diphenyl disulfide on novel cationic oxidative polymerization: examination of the electrophilic reaction of the cation by computational calculation

AbstractSubstituent groups of the diphenyl disulfides (DPSs) influence the cationic oxidative polymerization in the formation of polyphenylene sulfides (PPSs). A semiempirical MO calculation (AM1) was performed on the model compounds of PPS, such as thioanisoles (TAs) and diphenyl sulfides (PSs), in order to elucidate the reactivity of the cation. Linear PPS is formed on polymerization because of the high electron density of the carbon in the para position. The ratios of the frontier electron density of the carbon in the para position on the disulfide to the sulfur atom are ordered as follows; 3,5‐dimethyl‐PS>2,5‐dimethyl‐PS‐3‐methyl‐PS>nonsubstituted PS>2‐methyl‐PS>2,6‐dimethyl‐PS. The formation energies of the σ‐complex, which is the intermediate of the reaction, also shows the same order. The theoretical calculation indicates that 3,5‐dimethyl disubstituted disulfide and 3‐methyl one are most preferable monomers of this cationic oxidative polymerization.

Methylation of thioanisoles and anilines by 1-methyl-2,5-diphenyl-1,4-dithiinium tetrafluoroborate. Kinetics and correlations

Methylation of thioanisoles and anilines by 1-methyl-2,5-diphenyl-1,4-dithiinium tetrafluoroborate. Kinetics and correlations