Fluorinated 2-benzoylcyclohexane-1,3-diones and their vinylogous acyl chlorides in the reactions with primary and secondary amines

The reaction of 5,5-dimethyl-2-[(3-fluoro- and 4-fluoro)benzoyl]cyclohexane-1,3-diones with primary and secondary amines affords their exocyclic enamine derivatives. Under similar conditions 5,5-dimethyl-2-(2-fluorobenzoyl)]cyclohexane-1,3-dione undergoes dehydrofluorination and intramolecular cyclization to give 3,3-dimethyl-2,3,4,9-tetrahydro-1H-xanthene-1,9-dione. The reaction of vinylogous substitution of the enol derivatives of the fluorinated 5,5-dimethyl-2-benzoylcyclohexane-1,3-diones (vinylogous acyl chlorides) with amines results in the formation of the endocyclic enaminoderivatives.     

Five-membered 2,3-dioxo heterocycles: XCI. Reaction of 3-aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones with dimedone. Crystalline and molecular structure of 3′-benzoyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6,6-dimethyl-6,7-dihydrospiro[1-benzofuran-3,2′-pyrrole]-2,4,5′(1′H,5H)-trione

3-Aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones reacted with 5,5-dimethylcyclohexane-1,3-dione to give 3′-aroyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6,6-dimethyl-6,7-dihydrospiro[1-benzofuran-3,2′-pyrrole]-2,4,5′(1′H,5H)-triones. The crystalline and molecular structures of 3′-benzoyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6,6-dimethyl-6,7-dihydrospiro[1-benzofuran-3,2′-pyrrole]-2,4,5′(1′H,5H)-trione were determined by X-ray analysis.     

Building libraries of skeletally diverse scaffolds from novel heterocyclic active methylene compound through multi-component reactions

Libraries of skeletally diverse potential bioactive polycyclic/spirocyclic heterocyclic compounds; 2-amino-7,9-dimethyl-5-oxo-4-aryl-4,5,6,7-tetrahydropyrano[2,3-d]pyrazolo[3,4-b]pyridine-3-carbonitrile, 2′-amino-7′,9′-dimethyl-2,5′-dioxo-6′,7′-dihydro-5′H-spiro[indoline-3,4′-pyrano[2,3-d]pyrazolo[3,4-b]pyridine]-3′-carbonitrile, and 5,5′-(arylmethylene)bis(4-hydroxy-1,3-dimethyl-1H-pyrazolo[3,4-b]pyridin-6(7H)-one) have been synthesized through a multi-component reaction using novel heterocyclic active methylene compound 4-hydroxy-1,3-dimethyl-1H-pyrazolo[3,4-b]pyridine-6(7H)-one as one of the building blocks. This protocol can be considered to be an efficient and eco-friendly strategy for diversity oriented synthesis.     

Anti‐corrosion properties of bis(benzimidazole) derivatives for N80 steel in H2S solution

In this work, we systematically investigated the effect of four bis(benzimidazole) derivatives containing different heteroatoms in molecular structures on inhibiting corrosion of N80 steel in 0.5 mmol·l^?1 H₂S solution by potentiodynamic polarization, electrochemical impedance spectroscopy and metallographic microscope. The results showed that within the range of 0.1–1.0 mmol·l^?1, the adsorption of bis(benzimidazole) derivatives on N80 steel surface was found to follow Langmuir adsorption isotherm. Meanwhile, stable adsorbing monolayer between inhibitors and the metal surface was formed, which was confirmed by thermodynamic adsorption parameters (K_ads, ). This series of bis(benzimidazole) derivatives exhibited obvious corrosion inhibitory properties for N80 steel. Moreover, they could both slow down the anodic dissolution of iron and the cathodic reduction reaction as mixed type corrosion inhibitors. The optimal inhibition efficiency was obtained for 1,3‐bis(benzimidazl‐2‐yl)‐2‐thiapropane (BBMS). Hopefully, this series of inhibitors might find applications in anti‐corrosion and many other areas. Copyright © 2012 John Wiley & Sons, Ltd.     

Five-membered dioxo heterocycles: CIV. Reaction of methyl 1-aryl-3-benzoyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates with cyclic enehydrazines. Crystal and molecular structure of N-[3′-benzoyl-1′-(4-chlorophenyl)-4′-hydroxy-6,6-dimethyl-2,4,5′-trioxo-1′,4,5,5′,6,7-hexahydrospiro-[indole-3,2′-pyrrol]-1(2H)-yl]benzamide

Methyl 1-aryl-3-benzoyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates reacted with N′-(5,5-dimethyl-3-oxocyclohex-1-en-1-yl)benzohydrazides and N′-(5,5-dimethyl-3-oxocyclohex-1-en-1-yl)-2,2-diphenylacetohydrazide to give substituted N-[1′-aryl-3′-benzoyl-4′-hydroxy-6,6-dimethyl-2,4,5′-trioxo-1′,4,5,5′,6,7-hexahydrospiro[indole-3,2′-pyrrol]-1(2H)-yl]benz- and -diphenylacetamides.     

Synthesis of spirocyclic derivatives of azaphenanthrene containing a hydroxy-m-terphenyl fragment

The reaction of 5′-[(2-naphthylamino)methyl]-2′-hydroxy[1,1′:3′,1″]terphenyl with paraformaldehyde and 1,3-cyclohexanedione, methyl 2,2-dimethyl-4,6-dioxocyclohexanecarboxylate, dimedone, furan-2,4(3H,5H)-dione, indan-1,3-dione led to the formation of spiro derivatives of azaphenanthrene.     

Synthesis,X-ray structure and theoretical study of benzazole thioether and its zinc complex as corrosion inhibitors for steel in acidic medium

A ligand, 2-((benzo[d]thiazol-2-ylthio)methyl)-1H-benzo[d]imidazole, and its zinc complex have been synthesized. The structure of these compounds have been determined by spectroscopic techniques and single crystal X-ray diffraction. The corrosion inhibition study of these compounds for steel in 0.5 M H₂SO₄ medium has also been investigated using potentiodynamic polarization and EIS techniques. The quantum calculations were applied to investigate the relationship between the electronic properties and the corrosion inhibition efficiency of the two benzazoles derivatives. Surface analysis (XRF) indicated that the rust layer formed on the Cu-containing steels was enriched with Cu compounds. Polarization curves revealed that both inhibitors acted as a mixed-type inhibitor.     

Five-membered 2.3-dioxo heterocycles: LXVIII. Three pathways in the reaction of methyl 3-aroyl-1-aryl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates with 3-amino-5,5-dimethylcyclohex-2-en-1-one

Methyl 3-aroyl-1-aryl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates reacted with 3-amino-5,5-dimethylcyclohex-2-en-1-one having no substituent on the nitrogen atom to give 3-aroyl-4-arylamino-6′,6′-dimethyl-6′,7′-dihydro-5H-spiro[furan-2,3′-indole]-2′,4′,5′(1′H,5′H)-triones or methyl 12-aroyl-11-aryl-9-hydroxy-5,5-dimethyl-3,10-dioxo-8,11-diazatricyclo[7.2.1.0^2,7]dodec-2(7)-ene-1-carboxylates. The latter underwent thermal recyclization to 3′-aroyl-1′-aryl-4′-hydroxy-6,6-dimethyl-6,7-dihydrospiro[indole-3,2′-pyrrole]-2,4,5′(1H,1′H,5H)-triones.     

Synthesis,structure, and properties of new spirooxindolodibenzodiazepine derivatives

An acid-catalyzed reaction of 3-(2-aminophenylamino)-5,5-dimethylcyclohexen-1-one with isatines leads to the formation of the earlier undescribed 3,3-dimethyl-2,3,4,5,10,11-hexahydrospiro[1H-dibenzo[b,e][1,4]diazepine-11,3′-2H-indole]-1,2′-dione derivatives (6). Spiranes 6 upon heating undergo auto-redox rearrangement with disintegration to 3,3-dimethyl-1,2,3,4-tetrahydrophenazine and the corresponding oxindole. Crystals of four derivatives of compound 6 were studied by X-ray diffraction method.     

Reusable silica-bonded S-sulfonic acid catalyst for three-component synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromenes and 2-amino-4H-pyrans in aqueous ethanol

Silica-bonded S-sulfonic acid (SBSSA)-catalyzed, facile, one-pot, three-component coupling of 5,5-dimethyl-1,3-cyclohexanedione (dimedone) or 5,5-dimethyl-1,3-cyclohexanedione, aromatic aldehydes, and malononitrile at reflux temperature is described for preparation of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene derivatives. 2-Amino-3-cyano-6-methyl-4-phenyl-4H-pyran-5-ethylcarboxylate derivatives can also be prepared in good yield under the same experimental conditions by use of ethyl acetoacetate, aldehydes, and malononitrile. The catalyst, silica-bonded S-sulfonic acid, was reused and recycled without any loss of activity or product yield.     

An experimental and theoretical investigation on adsorption properties of some diphenolic Schiff bases as corrosion inhibitors at acidic solution/mild steel interface

The effect of novel synthesized three Schiff bases, namely, 1,3-bis[2-(2-hydroxy benzylidenamino) phenoxy] propane (P1), 1,3-bis[2-(5-chloro-2-hydroxybenzylidenamino) phenoxy] propane (P2), and 1,3-bis[2-(5-bromo-2-hydroxybenzylidenamino) phenoxy] propane (P3), on the corrosion of mild steel in 0.1 M HCl was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy methods. Polarization measurements suggest that P1 acts as mixed type inhibitor while P2 and P3 behave as mainly cathodic inhibitors for acidic corrosion of steel. All electrochemical measurements show that inhibition efficiencies increase with increase in inhibitor concentration. This reveals that inhibitive actions of inhibitors were mainly due to adsorption on steel surface. Adsorption of these inhibitors follows Temkin adsorption isotherm. The correlation between the adsorption ability of inhibitors and their molecular structures has been investigated using quantum chemical parameters obtained by MNDO semi-empirical method. Calculated quantum chemical parameters indicate that Schiff bases adsorbed on steel surface by chemical mechanism.     

Synthesis and reactions of pyrazole-4-carbaldehydes

1-, 3-, and 5-Alkylpyrazoles, as well as linearly bridged bis-pyrazoles, were converted into the corresponding 4-formyl derivatives by Vilsmeier-Haak reaction both under standard conditions and under microwave activation in DMF over a period of 10 min. 1,1′-(Hexane-1,6-diyl)bis(3,5-dimethyl-1H-pyrazole) and 1,1′-(benzene-1,4-diyldimethylene)bis(3,5-dimethyl-1H-pyrazole) gave rise to 4-formyl derivatives at both pyrazole rings. 5-Chloro-1,3-dialkyl-1H-pyrazoles failed to undergo formylation according to Vilsmeier-Haak or under microwave activation. 1,1′-Bridged bis-3,5-dimethyl-1H-pyrazoles reacted with 2-sulfanylethanol on heating in the presence of chloro(trimethyl)silane to give the corresponding bridged bis-4-(1,4,6-oxadithiocan-5-yl)-1H-pyrazoles.     

Five-membered 2,3-dioxo heterocycles: LX. Reaction of 3-aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones with cyclic enehydrazino ketones. Crystalline and molecular structure of N-[3′-benzoyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6, 6-dimethyl-2,4,5′-trioxo-1′,4,5,5′,6,7-hexahydrospiro[indole-3,2′-pyrrol]-1(2H)-yl]-3-nitrobenzamide

3-Aroyl-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones react with N′-(5,5-dimethyl-3-oxocyclohex-1-en-1-yl)benzohydrazides to give the corresponding N-[3′-aroyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6,6-dimethyl-2,4,5′-trioxo-1′,4,5,5′,6,7-hexahydrospiro[indole-3,2′-pyrrol]-1(2H)-yl]benzamides. The molecular and crystalline structure of one of the products, N-[3′-benzoyl-4′-hydroxy-1′-(2-hydroxyphenyl)-6,6-dimethyl-2,4,5′-trioxo-1′,4,5,5′,6,7-hexahydrospiro[indole-3,2′-pyrrol]-1(2H)-yl]-3-nitrobenzamide, was determined by X-ray analysis.     

Performance of some thiophene derivatives as corrosion inhibitors for 304 stainless steel in aqueous solutions

The inhibitive effect of 2-cyano-3-hydroxy-4(Ar)-5-anilino thiophene derivatives on the corrosion of 304 stainless steel (SS) in 3 M HCl solution has been investigated by weight loss, galvanostatic polarization techniques, and potentiodynamic anodic polarization in 3.5 % NaCl. The results indicate that these compounds act as inhibitors retarding the anodic and cathodic corrosion reactions. The presence of inhibitors does not change the mechanism of either hydrogen evolution reaction or SS dissolution. The activation energy and some thermodynamic parameters are calculated and discussed. These compounds are mixed-type inhibitors in the acid solution, and their adsorption on the SS surface is found to obey the Temkin adsorption isotherm. The results suggest that the percentage inhibition of these thiophene derivatives increases with increasing inhibitor concentration and decreases with increasing temperature. The synergistic parameter (S) was calculated and found to have a value greater than unity, indicating that the enhanced inhibition efficiency caused by the addition of I^?, SCN^?, and Br^? is only due to a synergistic effect. The relationship between molecular structure and inhibition efficiency was elucidated by quantum-chemical calculations using semi-empirical self-consistent field (SCF) methods.     

Corrosion inhibition of mild steel by highly stable polydentate schiff base derived from 1,3- propanediamine in aqueous acidic solution

Recently, the hydrolysis of Schiff bases under experimental conditions gives suspicion for their corrosion inhibition performance. The current study employs a stable Schiff base namely, 2,2′-{propane-1,3-diylbis[azanylylidene (E) methanylylidene]}bis(6-methoxyphenol) (LPD) as corrosion inhibitor for mild steel (MS) in 1 M HCl solution. The presence of the characteristic peak of the imine group in UV-visible spectra was taken as an indicator for LPD stability in acidic media. The inhibition action was examined using electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) besides gravimetric measurement. The inhibition efficiency reached 95.93 % for 0.75 mM LPD after 24 h of immersion at 25 °C. This high efficiency is owing to the presence of the characteristic imine group and other heteroatoms and π- electrons of the aromatic benzene rings. The mechanism of inhibition depends on adsorption phenomena on mild steel surface which obeys Langmuir isotherm model. The calculated values of adsorption equilibrium constant (K_ads), adsorption free energy ΔG_ads, adsorption enthalpy ΔH_ads and adsorption entropy ΔS_ads indicated spontaneous exothermic adsorption process of both physical and chemical nature. By rising temperature, the inhibition efficiency of LPD was decreased. The calculated activation energy was increased as the concentration of LPD increased. LPD was considered as a mixed-type inhibitor as indicated from PDP measurements. The obtained surface morphology and composition analysis using SEM/EDS, AFM and FTIR techniques ensures the high efficiency of LPD as corrosion inhibitor.     

Extracts of Punica granatum Linne husk as green and eco-friendly corrosion inhibitors for mild steel in oil fields

Extracts of pomegranate have been investigated, by use of weight loss and potentiodynamic polarization techniques, as green and eco-friendly inhibitors of corrosion of Q235A steel in 1 M hydrochloric acid solution at 60 °C. The efficiency of inhibition by the extracts varied with extract concentration from 10 to 1,000 mg/L; the highest efficiency was 95.0 %. The extracts inhibit corrosion mainly by an adsorption mechanism. In addition, the hydroxyl and ether groups of polyphenols can capture the H⁺ to reduce the corrosion, and the polyphenols can eliminate dissolved O₂ to inhibit oxygen-adsorption corrosion. Potentiodynamic polarization studies show that extracts are mixed-type inhibitors.     

Five-membered 2,3-dioxo heterocycles: LXIII. Cascade recyclization of isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates with cyclic enamines. Crystalline and molecular structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenylamino)methylidene]-6′,7′-dihydro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone

Isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates reacted with N-substituted 3-amino-5,5-dimethylcyclohex-2-en-1-ones to give the corresponding 1′-substituted (Z)-6′,6′-dimethyl-3-[phenyl(arylamino)methylidene]-6′,7′-dihydro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraones. The structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenylamino)methylidene]-6′,7′-dihydro-3Hspiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone was proved by X-ray analysis.     

1,7′-dimethyl-2′-propyl-1<Emphasis Type="Italic">H</Emphasis>,3′<Emphasis Type="Italic">H</Emphasis>-2,5′-bibenzo[<Emphasis Type="Italic">d</Emphasis>]imidazole as a corrosion inhibitor of mild steel in 1 M HCl

Inhibition effect of imidazole derivative 1,7′-dimethyl-2′-propyl-1H,3′H-2,5′-bibenzo[d]imidazole (DPBI) against mild steel corrosion in 1 M HCl solutions was evaluated using the conventional mass loss method, potentiodynamic polarization, linear polarization, and electrochemical impedance spectroscopy. The mass loss results showed that DPBI is an excellent corrosion inhibitor; electrochemical polarizations data revealed the mixed mode of inhibition; and the results of electrochemical impedance spectroscopy showed that the change in the impedance parameters, charge transfer resistance, and double layer capacitance with the change in the concentration of the inhibitor is due to the adsorption of the molecule leading to the formation of a protective layer on the surface of mild steel. The inhibition action of this compound was assumed to occur via adsorption on the steel surface through the active centers of the molecule.     

Experimental and Theoretical Studies on Synthesized Compounds as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

Imidazole derivatives, namely, 1-((1-(piperazinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (PBIP), and 1-((1-(morpholinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (MBIP) were synthesized and investigated as inhibitors for mild steel corrosion in 15% HCl solution using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. It was found that the inhibition efficiency of both the inhibitors increases with increase in concentration of inhibitors and decreases with increase in temperature. The inhibitors, PBIP and MBIP, show corrosion inhibition efficiency of 92.6% and 91.4% at 300 ppm concentration, respectively, at 303 K. Polarization studies showed that both the studied inhibitors were of mixed type in nature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed for surface study of uninhibited and inhibited mild steel samples. The semi-empirical AM1 method was employed for theoretical calculations.     

Experimental and theoretical studies of acridine orange as corrosion inhibitor for copper protection in acidic media

The corrosion process commonly limits the use of copper in practical applications. The use of corrosion inhibitors is one of the effective methods to reduce the corrosion rate of copper. In this research, the inhibition effect of acridine orange (3,6-bis(dimethylamine)acridine) (AcO) for the protection of copper in 0.5 ?M ?H₂SO₄ solution was studied. For this aim, the change of open circuit potential with exposure time (E_ocp-t), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), anodic and cathodic potentiodynamic polarization measurements (PP) and chronoamperometry (CA) techniques were used. Some quantum chemical parameters (E_HOMO, E_LUMO and dipole moment) were calculated and discussed. The AcO film formed over the copper surface was examined by SEM, EDX, AFM and contact angle measurements. The electrochemical data showed that AcO is an effective corrosion inhibitor even at low concentrations (ranging between 99.1% and %99.4 ?at concentrations from 0.01 ?mM to 1 ?mM). The corrosion rate of copper decreases in the presence of the inhibitor by reducing both anodic and cathodic rates, which is depended on its concentration. This compound behaves as mixed-type corrosion inhibitors with predominantly cathodic type. Its adsorption on the copper surface obeys Langmuir adsorption isotherm. The value of adsorption equilibrium constant (K_ads) and the standard free energy of adsorption were ΔG_ads 1.298 x 10³ ?M^?1 and -27.71 ?kJ/mol in the case of 0.5 ?M ?H₂SO₄ solution containing 1.0 ?mM AcO, which shows the adsorption is high and spontaneous. The adsorbed inhibitor film over the metal increase contact angle of the surface, which suggests the more hydrophobic properties of the surface are increasing coming from the orientation of hydrophobic sites to the electrolyte. The zero charge potential (E_pzc) studies showed that the surface charge of the metal is positive in the corrosive media containing the inhibitor. Quantum chemical calculations showed that the binding of inhibitor molecules to the metal surface takes place through N atoms of the inhibitor.