Trifluoroperacetic Acid Research Articles

Mechanistic Investigations on the Direct Regioselective Sulfonation of Gaseous Light Hydrocarbons by Sulfur Dioxide

Gaseous light hydrocarbons (LHs) are traditionally used as fuels, while their functionalization leads to wide applications of high economical values. Presented herein is the direct sulfonation of gaseous LHs by using SO2 and O2 gases. The in situ generated trifluoroperacetic acid (TFAOOH) and bis(trifluoroacetyl) peroxide ((TFAO)2) furnished the radical propagators trifluoroacetoxyl radicals (TFAO•) and HO•. The resultant trifluoroacetylsulfuric acid (TFAOSO3H) efficiently sulfonated LHs under mild conditions and in good chemoselectivities.

Synthetic Studies of Isoschizogamine: Alternative Preparation of the Key Intermediate.

An alternative synthetic route toward a key intermediate in the total synthesis of isoschizogamine is described. The Claisen-Johnson rearrangement stereoselectively constructed a quaternary carbon. Trifluoroperacetic acid mediated the Baeyer-Villiger oxidation to form a bicyclic lactone. The Mukaiyama-Matsuo protocol converted the lactone into an α,β-unsaturated lactone, that was used as the substrate for the rhodium-mediated 1,4-addition of an arylboronic acid.

Preparation of Vitamin E Intermediate from an Inexpensive Substrate by Selective Oxidation of Pseudocumene in HCOOH–H2O2 System

In this paper, 2,3,5-trimethyl-1,4-benzoquinone (TMBQ) was synthesized through the direct oxidation of 1,2,4-trimethylbenzene (pseudocumene, TMB) in the HCOOH–H2O2 system. The influence of three active species was studied, including performic acid (PFA) generated in formic acid, peracetic acid (PAA) generated in acetic acid, and trifluoroperacetic (TFPA) acid generated in trifluoroacetic acid. The effects of sulfuric acid and sodium formate addition were investigated, the over-oxidation of TMB was discussed, and the main reason for the decreasing selectivity was revealed. The oxidation of TMB can be controlled and improved through adjusting the reaction temperature, mole ratio of oxidant to substrate, and reactant concentration. The TMBQ yield of 28% was achieved with a TMB concentration of 0.2 mol/L, H2O2/TMB mole ratio of 6:1, and reaction temperature 37 °C. The selectivity of 72% was obtained with a TMB concentration of 0.2 mol/L, H2O2/TMB mole ratio of 5:1, and reaction temperature of 27 °C. The reaction mechanisms were proposed and discussed based on the gas chromatography–flame ionization detection (GC–FID) and gas chromatography–mass spectrometer (GC–MS) results.

Azido and Tetrazolo 1,2,4,5‐Tetrazine N‐Oxides

AbstractThis study presents the synthesis and characterization of the oxidation products of 3,6‐diazido‐1,2,4,5‐tetrazine (1) and 6‐amino‐[1,5‐b]tetrazolo‐1,2,4,5‐tetrazine (2). 3,6‐Diazido‐1,2,4,5‐tetrazine‐1,4‐dioxide was produced from oxidation with peroxytrifluoroacetic acid, and more effectively using hypofluorous acid, and 2 can be oxidized to two different products, 6‐amino‐[1,5‐b]tetrazolo‐1,2,4,5‐tetrazine mono‐N‐oxide and di‐N‐oxide. These N‐oxide compounds display promising performance properties as energetic materials.

Azido and Tetrazolo 1,2,4,5-Tetrazine N-Oxides.

This study presents the synthesis and characterization of the oxidation products of 3,6-diazido-1,2,4,5-tetrazine (1) and 6-amino-[1,5-b]tetrazolo-1,2,4,5-tetrazine (2). 3,6-Diazido-1,2,4,5-tetrazine-1,4-dioxide was produced from oxidation with peroxytrifluoroacetic acid, and more effectively using hypofluorous acid, and 2 can be oxidized to two different products, 6-amino-[1,5-b]tetrazolo-1,2,4,5-tetrazine mono-N-oxide and di-N-oxide. These N-oxide compounds display promising performance properties as energetic materials.

Total synthesis of (+)-iresin.

The first asymmetric total synthesis of (+)-iresin (4), an historically important ent-Drimane sesquiterpene lactone, was realized from aldehyde 3 via cyclic orthoester 6 in 5 steps. Notable transformations in this synthesis include a tandem trifluoroperacetic acid (TFPAA)-mediated Baeyer-Villiger oxidation-olefin epoxidation-epoxy ester cyclization, regioselective Burgess dehydration, and regioselective Fétizon oxidative lactonization.

Electron transfer in the peroxytrifluoroacetic acid-assisted sulfoxidation and oxidative destruction of benzhydryl sulfides

The reactions of benzhydryl sulfides Ph2CHSCH2R (R = H, CONH2, COOH, CN) with peroxytrifluoroacetic acid in CF3COOH were studied experimentally and by the quantum chemical density functional theory (DFT) method and exhibited an unusual dependence on the substituent R. When R≠H, a complicated oxidative destruction of the substrates occurs to form 2,4,6-tribenzhydrylphenol as one of the products, while in the case of R = H, the starting benzhydryl sulfide is smoothly sulfoxidated. This fact is due to the common electron transfer from the substrate to reagent at the initial step and the difference in subsequent transformations of the species formed.

Nitroalkanes as Key Compounds for the Synthesis of Amino Derivatives

The carbanion stabilizing effect of the nitro group makes nitroalkanes ideal reagents in carbon-carbon bond formation. Once introduced in a molecular framework, the nitro group is amenable to further transformations including reduction to primary amines. The aim of this review is to explore the utilization of nitroalkanes as effective substrates for the preparation of important target compounds featured by the amino group. These will include simple primary amines, diamines, amino acids, piperidines, pyrrolidines and heteroaromatic derivatives. A particular emphasis will be placed on the synthesis of enantioenriched amino derivatives mediated by organocatalysts or organometallic complexes. Keywords: Amines, asymmetric synthesis, nitroalkanes, nucleophilic additions, reductions, peroxytrifluoroacetic acid, urea-hydrogen peroxide complex, trifluoroacetic anhydride, anti cancer drug threo-dihydrosphingosine, adrenoceptor, norphenylephrine, antihypertensive drug, ritodrine, retroaldol process, enantioselective aza-Henry reaction

Stereoselective Synthesis of 4-Substituted 4-Hydroxypiperidines via Epoxidation-Ring Opening of 4-Methylenepiperidines

Reaction of 9-methylene-3-azabicyclo[3.3.1]nonanes with trifluoroperacetic acid results in stereoselective epoxidation to give the syn-epoxide. Intermolecular hydrogen bonding between the protonated tertiary amine and the peracid is responsible for the high levels of stereoselectivity.

ChemInform Abstract: Oxidation of 3,4-Di-tert-butylthiophene 1,1-Dioxide.

The oxidation of 3,4-di-tert-butylthiophene 1,1-dioxide (4) by a variety of reagents under various conditions was investigated in details. Oxidation of 4 with peracids (MCPBA, trifluoroperacetic acid) affords the thiete 1,1-dioxide 6 and the sulfone 7, both in moderate yield. The formation of these compounds can be explained as being the result of an acid-catalyzed rearragement of the initial product, expoxy sulfone 5 via the carbocation 8. Under basic conditions the rearrangement is suppressed and thus 5 can be isolated in good yield. Treatment of 5 with BF 3 •Et 2 O affords 6 and the sultine 10. Oxidation of 4 with alkaline H 2 O 2 involves a smooth Michael addition of HOO − to give the hydroxyperoxide 17 in high yield

ChemInform Abstract: 2-Sulfiliminopyridines and Their Oxidation to 2-Nitropyridines.

Sulfilimines of the pyridine series with electron-acceptor substituents in the ring were synthesized. It was shown that their oxidation with trifluoroperacetic acid results in the corresponding nitropyridines. The limitations of the methods were indicated.

Efficient stereocontrolled synthesis of (S)-Fmoc-β-nitroalanine via oxidation of oxime

Abstract Stereocontrolled synthesis of (S)-Fmoc-β-nitroalanine (20) was accomplished from (R)-Fmoc-Ser(tBu)-OH (14) in a total of six steps via an oxime. The oxime (17) was obtained from (R)-Fmoc-Ser(tBu)-H (16), which in turn was obtained by reduction of Weinreb amide (15). Oxidation of oxime was realized with peroxytrifluoroacetic acid at a neutral pH at 0 °C. After removal of the tBu protecting group with 90% TFA/H2O, the hydroxyl group was oxidized with Jones reagent to afford (S)-Fmoc-β-nitroalanine (20) in overall good yield.

Oxygen-Doped Nanodiamonds: Synthesis and Functionalizations

Oxadiamondoids representing a new class of carbon nanoparticles were prepared from the respective diamondoid ketones via an effective two-step procedure involving addition of methyl magnesium iodide and oxidation with trifluoroperacetic acid in trifluoroacetic acid. The reactivities of the oxacages are determined by the position of the dopant and are in good agreement with computational predictions.

Models for the enzymatically active state of cytochrome p-450

Ab initio and semiempirical molecular orbital calculations are made for a heme-containing model of the biologically active state of cytochrome P-450 and for two chemical models of the enzyme, chromyl chloride (CrO2Cl2) and peroxytrifluoroacetic acid (CF3COOOH), known to yield similar oxidation products. The heme model for the transient activated state of P-450 is made by analogy to a more stable active complex (compound I) formed by another heme enzyme, horse radish peroxidase with peroxides. The main aim of these studies is to characterize the active state, and in particular the electrophilic oxygen transferred to substrates by these enzymes. All models for the active state of P-450 have negatively charged oxygen atoms and low-energy virtual or half-filled orbitals with substantial oxygen character. These combined results suggest that the electrophilic activity of the oxygen in all these compounds is related to overlap rather than charge-controlled interactions with nucleophilic substrates. Calculations for a model of compound I itself yield a π cation porphyrin radical with two unpaired electrons in highly covalent nearly degenerate (dπ–Oπ) iron-oxygen orbitals. Electric field gradients and quadrupole splittings calculated for both compound I and its reduced form (compound II) are in good agreement with experiment.

A safe, convenient and efficient method for the preparation of heterocyclic N-oxides using urea·hydrogen peroxide

A novel, convenient, and high-yielding method has been developed for the preparation of heterocyclic N-oxides. The reaction uses the urea·hydrogen peroxide addition complex as a peroxide source for the in situ generation of trifluoroperacetic acid. The advantages of this method are easy handling of a stable, solid oxidant; high yields and simple removal of excess reagents and by-products.

A General Approach to Chemical Modification of Single-Walled Carbon Nanotubes with Peroxy Organic Acids and Its Application in Polymer Grafting

The previous work on the functionalization of single-walled carbon nanotubes (SWCNTs) with peroxytrifluoroacetic acid under ultrasonication is extended to other peroxy organic acids including m-chloroperbenzoic acid and 2-bromo-2-methylperpropionic acid (BMPPA). Systematic characterization of the treated SWCNTs shows that oxygen-based functional groups and the ester groups with Cl or Br substituents were introduced to the nanotubes, demonstrating that the peroxy organic acid treatment is a general approach to chemical modification of SWCNTs. The extent of functionalization depends on the acidity, oxidizability, and concentration of the peroxy organic acids. Furthermore, the attached reactive moieties allow the chemical coupling of SWCNTs to other materials. By using BMPPA-SWCNTs as the initiator, poly(methyl methacrylate) was grafted to SWCNTs through atom transfer radical polymerization.

The mechanism of the Baeyer–Villiger rearrangement: quantum chemistry and TST study supported by experimental kinetic data

The mechanism of the Baeyer-Villiger rearrangement is modelled for the reaction of propanone with trifluoroperacetic acid, catalyzed by trifluoroacetic acid in dichloromethane, using three DFT methods (B3LYP, BH&HLYP and MPWB1K) and MP2. These results are refined and used to calculate the overall reaction rate coefficient using conventional Transition State Theory. The excellent agreement between the calculated (1.00 x 10(-3) L mol(-1) s(-1)) and the experimental (1.8 x 10(-3) L mol(-1) s(-1)) rate coefficients at the MPWB1K level strongly supports the mechanism recently proposed by our group. This DFT method is then used to study the mechanism of a larger system: cyclohexanone + trifluoroperacetic acid, for which a very good agreement between the calculated and the experimental rate coefficients is also found (1.37 and 0.32 L mol(-1) s(-1), respectively). The modelled mechanism is not ionic but neutral, and consists of two concerted steps. The first one is strongly catalyzed while the second one, the migration step, seems not to be catalyzed for the systems under study. The results of this work could be of interest for understanding other reactions in non-polar solvents for which ionic mechanisms have been assumed.

Hybrid silica monolithic column for capillary electrochromatography with enhanced cathodic electroosmotic flow

A hybrid silica monolithic stationary phase for RP CEC was prepared by in situ co-condensation of (3-mercaptopropyl)-trimethoxysilane (MPTMS), phenyltriethoxysilane (PTES), and tetraethoxysilane (TEOS) via a sol-gel process. The thiol groups on the surface of the stationary phase were oxidized to sulfonic acids by peroxytrifluoroacetic acid. The introduced sulfonic acid moieties on the monoliths were characterized by a strong and relatively stable EOF in a broad pH range from 2.35 to 7.0 in CEC. Aromatic acids and neutral compounds can be simultaneously separated in this column under cathodic EOF. The CEC column exhibited a typical RP chromatographic mechanism for neutral compounds due to the introduced phenyl groups.

Peracid dependent stereoselectivity and functional group contribution to the stereocontrol of epoxidation of ( E)-alkene dipeptide isosteres

Twelve Boc-protected phenylalanyl-phenylalanine and phenylalanyl-glycine trans-vinyl isosteres were epoxidised with magnesium monoperoxyphtalate hexahydrate (MMPP) and trifluoroperacetic acid, and the results have been compared with those from earlier studies on epoxidations with m-CPBA. The alkenes were synthesised in high yields with high E/ Z-selectivities using either the Julia or Schlosser reactions. The formation of threo isomers was favoured in all epoxidation reactions except with CF 3CO 3H on substrates containing two allylic/homoallylic functional groups directing the peracid to opposite faces of the alkene. The switch to erythro selectivity observed with CF 3CO 3H is suggested to emanate from coordination to the allylic ester functionalities via hydrogen bond donation from the peracid. The other peracid reagents seem to be preferentially coordinated to the allylic carbamate function. The contribution of individual functional groups to the stereopreference was also investigated.

N-Nitroso- and N-Nitraminotetrazoles

N-Nitroso- (5a,c) and N-nitraminotetrazoles (6a-c) were synthesized from the corresponding aminotetrazoles (3a-c) either by the direct nitration with acetic anhydride/HNO3 or by dehydration of the corresponding nitrates (4a-c) with concentrated sulfuric acid. The conversion of the N-nitrosoaminotetrazoles (5a,c) with peroxytrifluoroacetic acid (CF3CO3H) yielded the corresponding nitramines in high yield (6a (82%), 6c (80%)). The N-nitroso- (5a,c) and N-nitraminotetrazoles (6a-c) have been fully characterized by vibrational (IR, Raman) and multinuclear NMR spectroscopy (14N/15N, 1H, 13C), mass spectrometry, and elemental analysis. A detailed discussion of the 15N chemical shifts and 1H-15N coupling constants is given. The molecular structures in the solid state were determined by single-crystal X-ray diffraction (3a,c; 5a,c; 6a-c) and a detailed discussion of the molecular structures will be presented. Furthermore, the structure and bonding as well as N,N rotational barriers are discussed on the basis of theoretically obtained data (B3LYP/6-31G(d,p), NBO analysis). In the case of two N-nitraminotetrazoles (6a,c) the physicochemical properties (e.g., D, P, delta(f)H degrees) were evaluated. The heat of formation was calculated to be positive for 6a and 6c (+2.8 and +85.2 kcal mol(-1), respectively) and the calculated detonation velocity with 5988 (6a) and 7181 (6c) m s(-1) reaches values of TNT and nitroglycerin.