Oxidation of alkenyldisilanes by m-chloroperbenzoic acid

Oxidation of vinylpentamethyldisilane by m-chloroperbenzoic acid (MCPBA) yields 1-(α,β-epoxyethyl)-1,1,2,2,2-pentamethyldisilane as major product. Conversely, the oxidation of allylpentamethyldisilane yields approximately equal amounts of allylpentamethyldisiloxane and 3-pentamethyldisilanylpropanal. These results have been accounted for in terms of the relative rates of oxidation of the various carboncarbon double bonds and siliconsilicon single bonds which have been determined.     

Synthesis of benzophenones from geminal biaryl ethenes using m-chloroperbenzoic acid

The oxidation of geminal biaryl ethenes 3 and 1,3-enynes 5 using m-chloroperbenzoic acid in dichloromethane at room temperature presents a catalyst-free approach for the synthesis of functionalized benzophenones 4 and ynones 6, respectively.     

Colorimetric and fluorescent signaling of Au3+ by desulfurization of thiocoumarin

We investigated the chemosignaling of Au(3+) by the selective desulfurization of thiocoumarin. In the presence of a heavy metal ion chelator N,N,N',N'-tetrakis-(2-pyridylmethyl)ethylenediamine, thiocoumarin was selectively converted to its oxo analogue by reaction with Au(3+), resulting in a pronounced chromogenic and fluorescent signaling. Selective signaling of Au(3+) was possible in the presence of common alkali, alkaline earth, and transition metal ions, as well as Au(+) in a mixed aqueous environment. The colorimetric determination of Au(3+) was possible by the color change from pink to yellowish green of the designed probe. The detection limit for the determination of Au(3+) in 50% aqueous acetonitrile was 1.1 × 10(-7) M.     

The reaction of bicyclic phosphine oxides,containing a hindered double bond with m-chloroperbenzoic acid

The reaction between m-chloroperbenzoic acid and phosphabicyclic phosphine oxides (e.g. 8-phenyl-8-oxo-8-phosphabicyclo[3.2.1]oct-6-ene) was investigated and the structure and stereochemistry of the compounds elucidated. It could be shown that compounds possessing the allyl-P(O) R(or Ar) site, in which the double bond is hindered enough to prevent a usual epoxidation, are oxidised by the peracid to the corresponding phosphinate. Furthermore, when the resulting compounds are still strained the phospinates are unstable. The suggested mechanism for the oxidation is a process similar to the Bayer-Villiger oxidation, which is known for ketones.     

PhI- and polymer-supported PhI-catalyzed oxidative conversion of ketones and alcohols to α-tosyloxyketones with m-chloroperbenzoic acid and p-toluenesulfonic acid

Various ketones were converted to the corresponding α-tosyloxyketones with mCPBA and p-toluenesulfonic acid in the presence of a catalytic amount of iodobenzene. Moreover, secondary alcohols were directly converted to the corresponding α-tosyloxyketones using mCPBA and catalytic amounts of iodobenzene and potassium bromide, followed by treatment with p-toluenesulfonic acid in a one-pot manner. Poly(4-iodostyrene) could be also used as a recyclable catalyst for the same α-tosyloxylation of ketone     

Selective signaling of peracetic acid over hydrogen peroxide by desulfurization of an anthracene-thioamide

Selective signaling of peracetic acid by desulfurization of a thioamide was investigated. A thioamide derivative of anthracene 1 was efficiently desulfurized by peracetic acid to the corresponding amide 2, which resulted in a pronounced turn-on type fluorescent signaling. Signaling was not affected by the presence of another important oxidant hydrogen peroxide thereby providing selective signaling of the peracetic acid from its frequent contaminant hydrogen peroxide. Anthracene-thioamide 1 also provided selectivity for peracetic acid over commonly encountered metal ions and anions. The chemical transformation was confirmed by ¹H NMR, ¹³C NMR, and fluorescence measurements.     

Fluorescent signaling of oxone by desulfurization of thioamide

The chemosignaling of the oxidant Oxone by selective desulfurization of a thioamide was investigated. Pyrene-thioamide was efficiently converted to its amide analogue by reaction with Oxone, resulting in a pronounced fluorescent turn-on type signaling. Selective signaling of Oxone in aqueous solution was possible in the presence of representative alkali and alkaline earth metal ions, as well as common anions.     

m-Nitrophenylarsonic acid as a polarographic reagent for titanium

A sensitive polarographic method for titanium, based on its selective and quantitative precipitation with polarographically reducible m-mtrophenylarsonic acid is described, factors affecting the quantitative precipitation — pH, concentration, of titanium and reagent, nature and concentration of anions, and digestion — have been studied.After precipitation of the titanium under controlled conditions, the precipitate is dissolved and the polarographic diffusion current of the organic reagent is related, by a calibration, to the original titanium concentration.The method has been applied successfully to the determination of titanium in complex high temperature alloys, after the removal of iron by a mercury cathode electrolysis.     

Selective fluorination of m-tyrosine by OF2

Fluorine-18 labeled aromatic amino acids are routinely used as tracers in positron emission tomography (PET) to study in vivo metabolic processes. The most versatile method for the production of such radiotracers is electrophilic fluorination of the aromatic amino acid with [¹⁸F]F₂, which is most commonly produced by the gas-phase nuclear reaction ¹⁸O(p, n)¹⁸F. Although [¹⁸F]F₂ is the major product, considerable amounts of [¹⁸F]OF₂ (up to 20%) are also produced. Electrophilic fluorination reactions of l-phenylalanine, 3-nitro-l-tyrosine, 4-nitro-dl-phenylalanine, 3,4-dihydroxyphenyl-l-alanine (l-DOPA), 3-O-methyl-l-DOPA, 3,4-dimethoxy-l-phenylalanine, p-tyrosine and o-tyrosine in H₂O and of m-tyrosine in anhydrous HF (aHF), CF₃SO₃H, CF₃COOH, CH₃COOH, HCOOH and H₂O using OF₂ were investigated. Although F₂ is an efficient fluorinating agent in aHF, electrophilic fluorination reactions using OF₂ were shown to be most efficient in less acidic media such as H₂O. In addition, and contrary to reports that OF₂ and F₂ have similar reactivities, m-tyrosine was the only aromatic system studied that was fluorinated by OF₂ and this was optimum in H₂O for the fluorinated m-tyrosine isomers (total yield, 4.35 ± 0.04%). The presence of [¹⁸F]OF₂ byproduct has no significant impact on the fluorination of aromatic amino acids investigated in this study and the subsequent production of their corresponding ¹⁸F-labeled radiotracers for patient use.     

A novel 4.6 5-connected metal-organic framework with strong fluorescent emission constructed by m-thioacetatebenzoic acid

A novel uninodal 5-connected metal-organic framework (MOF), [Cd₂L₂(4,4′-bipy)_3/2(H₂O)₂]_n (H₂L=m-thioacetatebenzoic acid and 4,4′-bipy=4,4′-bipyridine), was prepared under hydrothermal condition. It features an unusual brick-wall shape layer by 4,4′-bipy, which consists of right- and left-handed helical chains arrayed alternatively and finally expands by L^2- to a rare 5-connected nov (4⁴.6⁶) topology network. Photoluminescence study reveals that it displays intense structure-related fluorescent emission bands (λ_ex=355 nm) at 450 nm in the solid state at room temperature.     

Substituent effect of the spin-coupling constant through m-phenylene in m-xylylene and its derivatives

Density functional UB3LYP calculations with the broken symmetry approach and spin-projection method on m-xylylene diradical and its derivatives have been performed to investigate the dependence of the spin-coupling constant through m-phenylene on the number of phenyl substituents on the two radical sites. The results show that the coupling constant (or the singlet-triplet gap) steadily decreases on increasing the number of phenyl substituents on the two radical sites. This trend is ascribed to more spin delocalization into the phenyl substituents and the larger twist angle of the phenyl substituents out of the m-phenylene plane when the degree of phenyl substitution is increased. For Schlenk's hydrocarbon, the coupling constant J is 1.52 kcal/mol, only one quarter of that in the parent m-xylylene.     

Azodioxy-carbonyl compounds by oxidation of cyclic imines with m-CPBA

This article reports a simple and efficient synthesis of C-nitroso compounds (azodioxy esters or ketones and oximes) through a double oxidation of cyclic imines (4,5-dihydrooxazoles and 3,4-dihydro-2H-pyrroles) with m-CPBA. C-Nitroso derivatives seem to be potential donors of nitric oxide, one of the most powerful biological messenger.     

Conformational analysis of bridgehead-substituted bicyclo[m.m.m]alkanes and bicyclo[8.8.n]alkanes

Conformational analyses of bicyclo[m.m.m]alkanes where m=1-10 and of bicyclo[8.8.n]alkanes where n=1-7 bearing methyl groups on the bridgeheads were carried out using a Monte Carlo search strategy. In the bicyclo[m.m.m]alkane series, greater variability was observed for the inter-bridgehead distance for larger values of m. This suggests that properly substituted bicyclo[8.8.8]hexacosanes or larger ring systems might serve as molecular springs.     

A one-pot sulfide to sulfone oxidation with m-chloroperoxybenzoic acid and sodium permanganate

A synthetic strategy towards [2-(1H-indol-5-yl)-6-morpholin-4-ylpyrimidin-4-yl]methylsulfones is described, utilising m-chloroperoxybenzoic acid and sodium permanganate in a one-pot sulfide-sulfone oxidation.     

One-pot synthesis of multifunctionalized m-terphenyls

A facile one-step synthetic protocol toward multifunctionalized m-terphenyls 5 and sulfonyl m-terphenyls 6 is developed from substituted chalcones 1 and allyl sulfone 2 in good yields via a [3C+3C] annulation. The NaH-mediated annulation features transition metal catalyst-free condition. Chalcones 1 with the functional groups tolerance are easily prepared via Claisen–Schmidt condensation of substituted benzaldehydes 3 with acetophenone 4 in a qualitative yield under an aqueous alkaline methanolic solution.     

Dilithium catalyst based on m-diisopropenylbenzene

Styrene polymerization under the action of dilithium-m-diisohexanylbenzene has been studied. It is assumed that the chains of “living” polymer, having two growing end-groups, are subject to intramolecular association. Electron absorption spectra of dilithium-m-diisohexanylbenzene and “living” polymer have been investigated.     

Simultaneous determination of urinary hippuric acid, o-, m- and p-methylhippuric acids, mandelic acid and phenylglyoxylic acid for biomonitoring of volatile organic compounds by gas chromatography-mass spectrometry

A sensitive and precise method for the simultaneous determination of hippuric acid, o-, m- and p-methylhippuric acids, mandelic acid and phenylglyoxylic acid, which are major urinary metabolites of toluene, o-, m- and p-xylenes, styrene and ethylbenzene, respectively, was developed. These metabolites were converted into their methyl ester derivatives with methanol in hydrochloric acid, and then quantitated by gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring using a DB-1 capillary column. The injected compounds were quantitatively and reproducibly resolved within 19 min with a detection limit of 8-27 pg. The calibration curves were linear in the range of 0.05-25 μg for each compound, with correlation coefficients above 0.9999. This method was successfully used to analyze small amounts of both rat and human urine samples without any interference from coexisting substances. Overall recoveries of these compounds spiked in urine samples were 92-104%. The analytical results of the contents of these metabolites in the rat and human urine samples are presented.     

Fluorescence signaling of Zr4+ by hydrogen peroxide assisted selective desulfurization of thioamide

Thioamide derivative with a pyrene fluorophore was smoothly transformed to its corresponding amide by Zr(4+) ions in the presence of hydrogen peroxide. The transformation was evidenced by (1)H NMR spectroscopy and the signaling was completed within 10 min after sample preparation. Interference from Ag(+) and Hg(2+) ions in Zr(4+)-selective fluorescence signaling was readily suppressed with the use of Sn(2+) as a reducing additive. Discrimination of Zr(4+) from closely related hafnium, which is a frequent contaminant in commercial zirconium, was not possible. Prominent Zr(4+)-selective turn-on type fluorescence signaling was possible with a detection limit of 4.6 × 10(-6) M in an aqueous 99% ethanol solution.