Autoxidation of p-hydroxydiphenylamine

Autoxidation of p-hydroxydiphenylamine (HDPA) gives N-phenyl-p-benzoquinoneimine and hydrogen peroxide as primary products over a wide range of pH and the previously reported formation of N-(4-hydroxyphenyl)-p-benzoquinoneimine in basic media is in error. An induction period which is independent of substrate concentration but decreases with increase in pH is observed. The rate of oxidation is first order with respect to oxygen and half order with respect to HDPA. Oxygen is used in the system at the rate comparable to its rate of dissolution. On the basis of various kinetic parameters, a mechanism involving electron transfer to oxygen from HDPA anion and subsequent formation of HO₂ radical is postulated. The agreement of the experimental results with the derived rate expression is shown to support the mechanism.Singlet oxygen, produced in situ by methylene blue sensitization, leads to oxidation but with different products indicating that this species is not involved in the autoxidation.     

Synthesis and biological evaluation of triazepane derivatives as DPP-IV inhibitors

A series of triazepane derivatives such as (R)-3-amino-1-(1,2,5-triazepan-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-ones (7, 13a-p) and (R)-3-amino-1-(1,2,5-triazepan-5-yl)-4-(2,4,5-trifluorophenyl)butan-1-ones (17a-e) was synthesized and evaluated for their ability to inhibit dipeptidyl peptidase IV (DPP-IV) enzyme. Compounds with the acid moiety were found to be potent inhibitors of DPP-IV without inhibiting CYP 3A4. Among them, compound 13p ((R)-4-[1-acetyl-2-{3-amino-4-(2,4,5-trifluorophenyl)butanoyl-1,2,5-triazepan-5-carbonyl}benzoic acid]) showed a good in vitro activity without inhibiting CYP.     

Diarylnonanoids and their glucosides from Erica cinerea

The reinvestigation of Erica cinerea fresh aerial parts led to the isolation of two new diarylnonanoid aglycones along with their glucosides. From spectroscopic data, their structures were elucidated as rel-(3R,7R)-1,9-bis(p-hydroxyphenyl)-3,7-dihydroxynonan-5-one named ericanone, ericanone 3-β-d-glucoside, (3S)-3,7-anhydro-6,7-dehydroericanone and (3S)-3,7-anhydro-6,7-dehydroericanone 4′-β-d-glucoside. Contrary to the numerous diarylheptanoids more frequently distributed in the plant kingdom, the rare diarylnonanoids were previously restricted to the genus Myristica of the Myristicaceae plant family.     

Synthesis, structure, and antioxidant activity of hybrid N-substituted salicylic acid amides

Sterically hindered phenols, 3-tert-butyl-N-(3,5-di-tert-butyl-4-hydroxyphenyl)-5-ethyl-2-hydroxybenzamide and N-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propyl]-2-hydroxybenzamide, were synthesized as potential antioxidants, and the formation of hydrogen bonds by their molecules was shown by UV and IR spectroscopy.     

Two additional 1,9-diarylnonanoid 3-glucosides from Erica cinerea among which an unusual α-dione in conformational equilibrium

Continuation of the phytochemical analysis of Erica cinerea fresh aerial parts resulted in the isolation of two new compounds with a very close chromatographic behavior. On the basis of spectroscopic evidence (UV, MS and NMR), the structures were established as (−)-(3S,6E)-1,9-bis(p-hydroxyphenyl)-3-hydroxynon-6-en-5-one 3-O-β-d-glucoside named 6,7-anhydroericaone 3-O-β-d-glucoside and (−)-(3S)-1,9-bis(p-hydroxyphenyl)-3-hydroxynonan-5,6-dione 3-O-β-d-glucoside named α-ericadione 3-O-β-d-glucoside. Unanticipated by its α-alkadione type structure —a very unusual feature in the plant kingdom— the latter metabolite was found as a mixture of the minor s-cis and the major s-trans conformers. Moreover, the GC-MS analysis of the aglycone moieties of such glucosides, pointed out the permanent absence of the molecular ion and the constant hydroxybenzylium base peak, as well as the conversion of the α-dione into the major α-keto-enol tautomer.     

The carboxyl derivatives of 6,8-di-(tert.-butyl)phenoxazine: Synthesis,oxidation reactions and fluorescence

New carboxyl-containing o-aminophenols and phenoxazines were synthesized by condensation of 3,5-di-(tert.-butyl)-quinone with p-aminobenzoic and anthranilic acids. Oxidative transformations of the o-aminophenols and intermediate o-iminoquinones occur with the formation of the ESR detected phenoxazinyl radicals, which furthermore transform to phenoxazines or the dimeric products emerged through the radical attack at the C1 carbon of a formed phenoxazine. Molecular structure of the dimer obtained by oxidation of methyl ester of 4-[3,5-di-(tert.-butyl)-1-(2′-hydroxyphenyl)amino]benzoic acid was X-ray determined. Reaction of 4-[3,5-di-(tert.-butyl)-1-(2′-hydroxyphenyl)amino]benzoic acid with thionyl chloride gives rise to the formation of a derivative of 2-oxido-3H-benzo[d,j][1,2,3]oxathiazol system, the structure of which was established using X-ray crystallography. Solutions of methyl-6,8-di-(tert.-butyl)-10H-phenoxazine-3-carboxylate solvents display intense fluorescence covering a broad spectral region in the range of 400–600?nm.     

Multi-wall carbon nanotube-supported manganese(III) porphyrin: An efficient and reusable catalyst for the oxidation of alkenes with H2O2 under ultrasonic irradiation

A manganese complex of meso-tetrakis(p-hydroxyphenyl)porphyrin immobilized onto functionalized multi-wall carbon nanotubes has been synthesized and characterized. The catalytic activity of this heterogeneous catalyst was investigated in the oxidation of various olefins with hydrogen peroxide under ultrasonic irradiation. The role of the stoichiometric amounts of acetic anhydride/or acetic acid as an activator that introduces in situ peracetic acid is discussed. This heterogeneous catalyst was highly reusable in the oxidation reactions and reused several times without significant loss of its catalytic activity.     

Synthesis of new pyrazole-1,2,3-triazole dyads

An efficient two step synthetic methodology of new 5(4)-aryl-4(5)-[3(5)-(2-hydroxyphenyl)-1H-pyrazol-5(3)-yl]-1H-1,2,3-triazole dyads was established. The reaction of (E)-2-styryl-4H-chromen-4-ones, used as building blocks, with sodium azide, gave 4(5)-aryl-5(4)-(chromon-2-yl)-1H-1,2,3-triazoles bearing either electron-donating or electron-withdrawing substituents in their styryl moiety which upon reaction with hydrazine hydrate afforded the expected pyrazoles in moderate to very good yields.     

(E)-3-Halo-2-styryl-4H-chromen-4-ones: synthesis and transformation to novel pyrazoles

New methods for the synthesis of (E)-3-halo-2-styryl-4H-chromen-4-ones were established. The reaction of these compounds with hydrazine hydrate afforded new and unexpected 3(5)-aryl-5(3)-[2-(2-hydroxyphenyl)-2-hydrazonoethyl]-1H-pyrazoles, which upon acid hydrolysis gave 3(5)-aryl-5(3)-[2-(2-hydroxyphenyl)-2-oxoethyl]-1H-pyrazoles. The reaction mechanisms for these transformations, involving 1,6- followed by 1,4-conjugate additions, are discussed and the structures of all new compounds were established by NMR studies.     

Remarkable Chichibabin-type cyclotrimerisation of 3-nitrotyrosine, tyrosine and phenylalanine to 3,5-diphenylpyridine derivatives induced by hypochlorous acid

Reaction of 3-nitrotyrosine with HOCl in aqueous phosphate buffer (pH 7.4) leads to a mixture of extractable products, including 3,5-di(4-hydroxy-3-nitrophenyl)pyridine (15% isolated yield) and 3,5-di(4-hydroxy-3-nitrophenyl)-2-(4-hydroxy-3-nitrophenylmethyl)pyridine (3%) arising by a Chichibabin-like pyridine synthesis via N-chloroimine intermediates. Under the same conditions, phenylalanine gives 3,5-diphenylpyridine in 9% isolated yield, while tyrosine leads to 3,5-di(4-hydroxyphenyl)pyridine (3%) and 3-(3-chloro-4-hydroxyphenyl)-5-(4-hydroxyphenyl)pyridine (3%).     

Synthesis of liquid-crystalline substances from the 5-alkyl-5-arylisoxazole series

The oxidation of 3-(4-acetoxyphenyl)-5-pentyl-2-isoxazoline with N-bromosuccinimide followed by hydrolysis of the oxidation product furnished 3-(4-hydroxyphenyl)-5-pentyl-isoxazole. Its esterification or benzylation afforded the target liquid-crystalline 3-aryl-5-pentyl-isoxazoles.     

Modification of 2-trifluoromethyl-1H-benzimidazole with hydroxyalkyl substituents

Alkylation of 2-(trifluoromethyl)-1H-benzimidazole with 4-bromobutyl acetate gave 4-[2-(trifluoromethyl)-1H-benzimidazol-1-yl]butyl acetate which was deacylated by the action of hydrogen chloride in anhydrous ethanol. 4-[2-(Trifluoromethyl)-1H-benzimidazol-1-yl]butan-1-ol thus formed showed a moderate tuberculostatic activity. Alkylation of the title compound with chloromethyloxirane afforded a mixture of 1-chloro-3-[2-(trifluoromethyl)-1H-benzimidazol-1-yl]-propan-2-ol and 1-(oxiran-2-ylmethyl)-2-trifluoromethyl-1H-benzimidazole. A new procedure was proposed for the synthesis of 2-[(2-trifluoromethyl-1Hbenzimidazol-1-yl)methoxy]ethyl acetate.     

Oxidation and ring cleavage reactions of 3-benzhydrylchromones. Generation of triarylmethine cations from methylidenechroman-4-ones and benzopyrano[4,3-c]pyrazoles

The oxidation of 3-[bis-(diaryl)methyl]chromones 2 with p-chloranil affords novel acetals, 3-[bis-(diaryl)methylene]-2-methoxychroman-4-ones, 4 through interception of a pyrylium type intermediate. Oxidation of 3-(2-hydroxyphenyl)-4-[bis-(diaryl)methyl]pyrazoles 8, derived from 2 and hydrazines, gave 4,4-diarylbenzopyrano[4,3-c]pyrazoles 15. The electronic absorption spectra of 4 and 15 upon protonation are comparable with those of triarylmethine cationic dyes.     

The autoxidation of 2-(2-aminophenyl)-3- methylindole

Fischer indolisation of 2-aminophenyl ethyl ketone phenylhydrazone using glacial acetic acid saturated with hydrogen chloride as catalyst affords 3-methylindolo(l′:2′-3:4)2-methylquinazoline and 2-(2-aminophenyl)-3-methylindole. The latter compound is autoxidised to 2-(2-amino-phenyl)-3-hydroxy-3-methyl-3H-indole, a reaction which is shown to be dependent upon the presence of the primary amino group at the 2-position of the 2-phenyl substituent and which is much slower than the corresponding autoxidation of 2-(2-hydroxyphenyl)-3-methylindole to 3-hydroxy-2-(2-hydroxyphenyl)-3-methyl-3H-indole previously reported.Nitration of isopropyl phenyl ketone occurs preferentially at the ortho- rather than the meta- positions of the benzene nucleus.     

A facile synthesis and properties of quinone from a polyvalent porphyrin,tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)phorphyrin

The quinone 5,15-di-(3,5-di-tert-butyl-4-hydroxyphenyl)-10,20-di-(3,5-di-tert-butyl-4-quinomethane)porpho-10,20-dimethene (2) was obtained in high yield by the oxidation of the polyvalent porphyrin tetrakis(3,5-ditert-butyl-4-hydroxyphenyl)phorphyrin (1) with an Mn²⁺-O₂ system in dimethylformamide. 2 was reduced to 1 by ascorbic acid or hydroquinone.     

Synthesis of unsymmetrical phosphorus-containing macrocycles on the basis of hydroquinone, 4,4′-(propane-2,2-diyl)diphenol,and resorcinol

Bisphosphorylation of hydroquinone and 4,4′-(propane-2,2-diyl)diphenol was performed for the first time in ethyl acetate. The bisphosphorylated products were used in molecular assembly of unsymmetrical phosphorus(III)-containing macrocycles consisting of hydroquinone and 2,2-bis(p-hydroxyphenyl)propane or resorcinol fragments. The macrocyclic compound based on hydroquinone and 2,2-bis(p-hydroxyphenyl)-propane was subjected to oxidation and sulfurization to obtain the corresponding phosphorus(V) derivatives. Its biological activity was also studied.     

One-pot electrochemical synthesis of highly symmetric and conjugated coumarin derivative

A facile and one pot electrochemical synthesis of disubstituted hydroquinone generated from the electrochemical oxidation of 4-1-(4-(4-hydroxyphenyl)piperazin-1-yl)ethanone (1) in the presence of 4-hydroxy-6,7-dimethylcoumarin (3) has been reported. The results revealed that p-quinone imine derived from oxidation of (1) participate in Michael addition reactions with 3 and followed by a hydrolysis reaction attain to the highly symmetric and conjugated coumarin derivative. We derived a new product in good yield based on controlled potential electrochemical oxidation at carbon electrode in a divided cell.     

Electrophilic organic selenium reagents—protonated seleninic acids as precursors for unsymmetrical aromatic selenides

Arylselenylations of methylbenzenes, methoxybenzenes and thiophene were smoothly achieved with selenenium ions generated by comproportionation of 1:1 mixtures of p-toluenesulfonic acid salts of seleninic acids and the corresponding diselenides. A series of p-toluenesulfonic salts of seleninic acids were prepared by hydrogen peroxide oxidation of the corresponding diselenides in the presence of p-toluenesulfonic acid. Novel 2-(organylseleno)thiophenes were obtained by heating the protonated seleninic acids with a 50-fold excess of thiophene in glacial acetic acid.     

Reactions of 5-aryl-4-acyl-1-(4-hydroxyphenyl)-3-hydroxy-3-pyrrolin-2-ones with arylamines

The reaction of 5-(4-chlorophenyl)-4-benzoyl-1-(4-hydroxyphenyl)-3-hydroxy-3-pyrrolin-2-one with aromatic amines affords the corresponding 3-arylamino derivatives, and the reactions of 5-aryl-4-acetyl-1-(4-hydroxyphenyl)-3-hydroxy-3-pyrrolin-2-ones with p-toluidine yield 5-aryl-4-(1-p-tolylamino)ethylene-1-(4-hydroxyphenyl)pyrrolidin-2,3-diones.     

Electrochemical synthesis of new organic compounds based on the oxidation of 1,4-dihydroxybenzene derivatives in the presence of primary and secondary amines

An efficient method for the synthesis of 2-benzyl(4-hydroxyphenyl)amino)-6-(benzylamino)-p-benzoquinone derivatives and 2,5-bis-benzyl(methyl)amino)-p-benzoquinone based on the Michael type reaction is described. The electrochemically generated p-benzoquinone reacted with benzylamine derivatives (primary amines) and N-methylbenzylamine (a secondary amine), respectively, to produce the final products. In this work, some new symmetric and asymmetric p-benzoquinone derivatives are synthesized using green solvents with high yields.