Condensation Of O-aminophenol Research Articles

Selective oxidation of alcohols promoted by cis-Dioxomolybdenum (VI) ONO Complexes

Selective oxidation of alcohols to aldehydes in mild conditions remains an important reaction in organic synthesis, in this regard the use of molybdenum complexes of Schiff bases results in an effective improvement of the catalysis of this reaction. Several ONO Schiff bases were synthesized by condensation of o-aminophenol and the corresponding 5-substituted salicylaldehyde derivatives, further complexation with bis(acetylacetonato)dioxomolybdenum(VI) afforded the corresponding cis-dioxomolybdenum(VI) complexes which were fully characterized. These complexes were used as catalysts for the oxidation of several alcohols under solvent-free condition using H2O2 as oxidant with outstanding results. The electronic effects of the substituents in the catalytic process were studied concluding that strong electron withdrawing groups indeed facilitates the catalytic reaction. Furthermore, the scope of the methodology was evaluated showing good tolerance to other functional groups.

Schiff bases of 1,5-diarylpent-4-ene-1,3-diones and their metal complexes: Synthesis, characterization and fluorescent studies

Four Schiff bases (H2L1 to H2L4) were synthesized by the condensation of o-aminophenol and unsaturated diketones (1,5-diarylpent-4-ene-1,3- -diones). Analytical, IR, 1H-NMR and mass spectral data revealed their existence in the imine?enamine form. Dibasic tetradentate coordination of the Schiff bases in their ML complexes (M = Cu(II), Ni(II), Co(II), Zn(II), Cd(II), and Hg(II)) was established based on physical, analytical and spectral data. The fluorescent studies of H2L4 showed that the fluorescence emission maxima shifted with increasing polarity and hydrogen bonding ability of the solvent. Paramagnetic Cu(II), Ni(II) and Co(II) ions decrease the fluorescence intensity with increasing concentration of the metal ion while diamagnetic Zn(II), Cd(II) and Hg(II) ions have very little influence on the fluorescence intensity of the Schiff base H2L4.

Novel R3M (M = Si, Ge) substituted furan and thiophene-derived aldimines: Synthesis, electrochemistry, and biological activity

New furan and thiophene derivatives of aldimines o -HO-C 6 H 4 N CHC 4 H 4 X(R) (X = O, S; R = H, SiMe 3 , SiEt 3 , GeMe 3 , GeEt 3 ) were synthesized by condensation of o -aminophenol with the substituted aldehyde precursor. Their structure, electrochemical reduction/oxidation (in CH 3 CN/0.1 M Bu 4 NPF 6 ), frontier orbital energies, and cytotoxicity have been studied. Their electrochemical redox potentials E p show good correlation with the corresponding orbital energies and the difference E p ox – E p red corresponds well to their orbital hardness. These new compounds have a pronounced cytotoxicity toward cancer cells of human fibrosarcoma HT-1080 and mouse hepatoma MG-22A (IC 50 ≅ 1–8 μg ml −1 ) that can be modulated by introducing a Me 3 M substituent into the fifth position of the heterocycle (e.g., IC 50 (Me 3 Si)/IC 50 (H) ≥ 50). R 3 M-substitution reduces the orbital hardness of the aldimines studied and facilitates oxidation, promoting their oxidative metabolism. The neighboring group effect in the α-Me 3 Si-substituted thiophene derivative favors S-oxidation, which supposedly makes its metabolic mechanism different compared to R 3 M-substituted furan series (or for M = Ge in the thiophene series). Interestingly, SiMe 3 and GeMe 3 groups in both heterocyclic series (furan and thiophene) cause opposite trends in cytotoxicity, while the silyl group increases it, the germyl group decreases it. De nouvelles aldimines o -HO-C 6 H 4 N CHC 4 H 4 X(R) (X = O, S; R = H, SiMe 3 , SiEt 3 , GeMe 3 , GeEt 3 ), dérivées du furanne et du thiophène, ont été synthétisées par la condensation d' o -aminophenol avec l'aldéhyde précurseur substitué correspondant. La structure, la réduction et l'oxydation électrochimique (dans CH 3 CN/0.1 M Bu 4 NPF 6 ), les énergies des orbitales frontières et la cytotoxicité de ces composés ont été étudiées. Les potentiels redox électrochimiques E p de ces composés montrent une bonne corrélation avec les énergies orbitalaires correspondantes, et la différence E p ox – E p red correspond bien à leur dureté orbitalaire. Ces nouveaux composés ont une cytotoxicité prononcée sur les cellules du fibrosarcome humain HT-1080 et de l'hépatome de souris MG-22A (IC 50 ≅ 1–8 μg ml −1 ); elle peut être modulée par l'introduction d'un substituant Me 3 M en position 5 de l'hétérocycle (par exemple, IC 50 (Me 3 Si)/IC 50 (H) ≥ 50). Cette substitution réduit la dureté orbitalaire des aldimines étudiées et facilite leur oxydation en favorisant le métabolisme oxydatif. L'effet d'un groupe voisin dans le thiophène substitué en position α par Me 3 Si favorise son S-oxydation, ce qui vraisemblablement rend son mécanisme métabolique différent par rapport à celui des dérivés R 3 M-substitués dans la série du furanne (ou pour M = Ge dans la série du thiophène). Il est intéressant de noter que les groupements SiMe 3 et GeMe 3 dans les deux séries hétérocycliques (furanne, thiophène) ont des effets opposés sur la cytotoxicité: le groupement silyle l'augmente, tandis que le groupement germyle la réduit.

Phosphonium acidic ionic liquid: an efficient and recyclable homogeneous catalyst for the synthesis of 2-arylbenzoxazoles, 2-arylbenzimidazoles, and 2-arylbenzothiazoles.

A highly efficient and green strategy for the synthesis of 2-arylbenzoxazoles, 2-arylbenzimidazoles, and 2-arylbenzothiazoles catalyzed by phosphonium acidic ionic liquid has been developed via the condensation of o-aminophenol, o-phenylenediamines, and o-aminothiophenol, respectively, with aldehydes. The reaction has a good yield, the broad substrate scope, and mild condition. Triphenyl(butyl-3-sulphonyl)phosphonium toluenesulfonate catalyst was easily obtained from cheap and available starting materials through a one-pot synthesis. Its structure was identified by 1H NMR, 13C NMR, 31P NMR, and FT-IR techniques. Other properties including thermal stability and acidity were determined by TGA and Hammett acidity function method. Interestingly, the catalyst can maintain its constantly outstanding performance till the fourth recovery.

A Decade Update on Benzoxazoles, a Privileged Scaffold in ­Synthetic Organic Chemistry

In 2014, more than 80% of the marketed drugs in the US contained heterocyclic compounds, which play a major role in the drug-discovery process, as one of the primary components. Benzoxazole, consisting of an oxazole ring fused with a benzene ring, has shown profound impact in drug discovery research owing to its important bioactivity. This moiety has also shown important properties in material science. The synthesis of this privileged scaffold from readily available chemicals remains a primary focus for the synthetic chemistry community. In this review, efforts have been made to focus on the latest information available on the different synthetic strategies such as solution phase, multicomponent, green and solid phase chemistry and applications of different benzoxazole derivatives. Furthermore, the updated synthetic information incorporated in this review article will help to improve future synthesis of this scaffold. 1 Introduction 2 Solution-Phase Synthetic Approach to Substituted Benzoxazoles 2.1 Condensation of o-Aminophenol with Carboxylic Acids 2.2 Condensation of o-Aminophenol with Aldehydes 2.3 Condensation of o-Aminophenol with Orthoesters, ortho-Haloamides, or 1,1-Dihaloalkenes 2.4 Synthesis of Benzoxazoles from Schiff Bases 2.5 Miscellaneous 3 Multicomponent Synthetic Approach to Substituted Benzoxa­zoles 4 Solid-Phase Synthetic Approach to Substituted Benzoxazoles 5 Green Synthetic Approach to Substituted Benzoxazoles 5.1 Condensation of o-Aminophenol with Aldehydes 5.2 Condensation of o-Aminophenol with ortho-Substituted Benz­amides 5.3 Condensation of o-Aminophenol with Carboxylic Acid and its Derivatives 5.4 Condensation of o-Aminophenol with Alcohols or Amines 5.5 Miscellaneous 6 Bioactive Derivatives of Benzoxazoles 7 Conclusion and Outlook

Special features of preparing benzoaza-12-crown-4 by condensation of o-aminophenol with triethylene glycol dichloride

Preparative method of benzoaza-12-crown-4 preparation via condensation of o-aminophenol with trietylene glycol dichloride using sodium hydroxide as the template agent has been studied at elevated temperature in 2-propanol and n-butanol. Kinetics of the reaction mixture composition change in the course of the process has been investigated by GLC. Performing the reaction in 2-propanol leads to a higher yield of benzoaza-12-crown-4.

Synthesis and properties of 2-(2-furyl)-and 2-(2-Thienyl)-1,3-benzoxazoles

Condensation of o-aminophenol with furoyl and thenoyl chlorides in 1-methylpyrrolidin-2-one gave, respectively, 2-(2-furyl)- and 2-(2-thienyl)-1,3-benzoxazoles in which the furan and thiophene rings showed no acidophobic properties. Reactions of 2-(2-furyl)- and 2-(2-thienyl)-1,3-benzoxazoles with electrophilic reagents (acylation, bromination, nitration, and sulfonation) afforded products of hydrogen replacement in both hetaryl and benzene rings, depending on the conditions.

Synthesis of 2-arylbenzoxazoles via DDQ promoted oxidative cyclization of phenolic Schiff bases—a solution-phase strategy for library synthesis

The Schiff base derived from the condensation of o-aminophenol with benzaldehydes was induced to undergo oxidative cyclization in the presence of DDQ. The resulting 2-arylbenzoxazoles were separated from the reduced DDQ byproduct by treatment of reaction mixture with a strongly basic ion-exchange resin. The applicability of this chemistry to spatially separate library synthesis is demonstrated by the preparation of a 352-member library.

ChemInform Abstract: New Spin‐Crossover Iron(III) Complexes with Large Hysteresis Effects and Time Dependence of Their Magnetism.

AbstractVariable‐temp.

ChemInform Abstract: Synthesis of 1‐ and 4‐Substituted‐5H‐benzo(a)phenoxazin‐5‐ones.

AbstractReaction of o‐aminophenol (I) with the dichloronaphthoquinones (II) produces the benzophenoxazines (III) and (IV).

New spin-crossover iron(III) complexes with large hysteresis effects and time dependence of their magnetism

The new complexes [FeL12] ClO4(HL1= tridentate Schiff base formed by 1 : 1 condensation of o-aminophenol and pyridine-2-carbaldehyde) and [FeL22] NCS ( HL2= tridentate Schiff base formed by 1 : 1 condensation of 8-aminoquinoline and salicylaldehyde) were synthesized. The spin-crossover behaviour between S=½ and 5//2 which is dependent on temperature was observed for the solid complexes using variable-temperature 57Fe Mossbauer spectral and magnetic measurements. Both compounds show a pronounced hysteresis effect in the high spin ⇌ low spin transition. For [ FeL12] ClO4, sharp and strong Mossbauer absorptions were observed over the temperature range examined and the effective vibrating mass, Meff., was evaluated using the high-temperature approximation of the Debye model. The value for the low-spin isomer was larger than that for the high-spin isomer. The complex [FeL22]NCS when freshly recrystallized below 280 K is predominantly in a low-spin state. However, the magnetism at room temperature increases with time, spin-crossover behaviour is exhibited, and the magnetism is dependent on temperature, with a pronounced hysteresis loop of about 70 K at 286 K 10 d after preparation.

Synthesis of 1‐ and 4‐substituted‐5H‐benzo[a]phenoxazin‐5‐ones

AbstractThe 1‐ and 4‐substituted‐5H‐benzo[a]phenoxazin‐5‐ones (substitutents: nitro, amino and acetylamino) were prepared by the condensation of o‐aminophenol with 5‐substituted‐2,3‐dichloro‐1,4‐naphthoquinones. The resulting compounds were subjected to reduction, acetylation and dehalogenation.

Metal complexes of the Schiff base derived from ortho-aminophenol and ethyl acetoacetate containing similar and dissimilar metal atoms

The tridentate ligand (H 2L) of the NO 2 chromophore is prepared by the condensation of o-aminophenol and ethyl acetoacetate. This ligand comprises chelation sites (A) and (B) which involve the phenolic oxygen and the carbonyl oxygen of the β-diketone respectively. The immediate reaction of the ligand with Cu(II) acetate (1:1 or 2:1) produced the mixed ligand complex (1) [HL(CuCO 2CH 3)] 2, while the prolonged reaction (1:1) led to formation of the dimeric complex (2) (LCu) 2 in which the ligand behaves as a tridentate one. The reaction of the ligand with Cu(II) chloride (1:1) affords the complex (3) HL(CuCl). The metal atom is coordinated to the ligand through site (A) in complexes (1) and (3). The reactions of the two-coordinate oxygen atoms in complex (1) with the metal chlorides MCl 2 (1:2) produced the homo- and heteronuclear complexes which are formulated as [(LCu·LCu·H 2O)MCl 2] 2 for M = Cu(II), or Zn(II) and (LCu·H 2O·MCl 2·nH 2O) 2 for M = Mn(II), Co(II) or U(VI); n = 0, 0 and 2 respectively. The intermediate formation of complex (2) is suggested in these reactions. Analytical, spectral and magnetic moment evidence are compatible with the tentatively suggested formulations.

Synthesis and some reactions of 1-phenylimidazo'[5,1-b] benzoxazole

The condensation of o-aminophenol with ethyl hippurate has given 2-benzoylaminomethylbenzoxazole (I) and N-hippuroyl-o-aminophenol (II). The cyclization of both I and II in the presence of phosphorus oxychloride in benzene or toluene leads to the formation of 1-phenylimidazo[5, 1-b]benzoxazole (III). Compound III has been brominated in position 3 and has been subjected to the Mannich and Vilsmeier reactions. A number of derivatives of III containing various substituents in position 3 has been obtained.

Search for physiologically active compounds

2-aryl benzoxazoles have been prepared in good yield by the condensation of o-amino phenol with aromatic aldehydes in nitrobenzene medium. Starting from 4-nitro, 4-chloro and 5-nitro o-amino phenols, 5 and 6 substituted 2-aryl benzoxazoles have also been synthesised.

オキサツォール及びベンツオキサツォールの化学的性質 (第2報)

Benzoxazole gives 2-aminobenzoxazole when warmed with sodium amide and this compound was found to be identical with the substance obtained from o-aminophenol and cyanogen bromide. 2-Amino-5-ethoxyphenol and cyanogen bromide gave 6-ethoxybenzoxazole whose hydrochloride exhibited a local anesthetic action. 2-Methylbenzoxazole underwent condensation with benzaldehyde in the presence of zinc chloride to form 2-styrylbenzoxazole which was identical with the substance obtained by the condensation of o-aminophenol and cinnamic amide. 2-Methylbenzoxazole underwent condensation with benzyl chloride in the presence of sodium amide to form 2-β-phenylethylbenzoxazole which is also obtained by the catalytic reduction of the afore-mentioned 2-styryl derivative. Benzoxazole ring is opened by the application of benzoyl chloride in the presence of potassium cyanide to form o-benzoylaminobenzoylphenol. 2-Aminobenzoxazole does not undergo diazotation under conditions similar to those used for 2-aminobenzothiazole, and does not form imidazole derivative by the action of bromoacetophenone. Heating of 2-aminobenzoxazole and bromoacetophenone results in resinification, partly giving 2-acetaminophenol formed by ring fission, and not the pyrrol derivative.