- 2,4-dinitrophenyl ether-containing chemodosimeters for the selective and sensitive in vitro and in vivo detection of hydrogen sulfide
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Four probes (i.e. D1-D4) for the selective and sensitive fluorogenic detection of HS- have been prepared and characterised. HEPES (10 mM, pH 7.4)-DMSO 99:1 v/v solutions of D1-D4 are essentially non-fluorescent. Changes in the emission using D1-D4 in the presence of anions (F-, Cl-, Br-, I-,N-3, CN-, SCN-, AcO-,CO2-3 ,PO2-4,SO2-4, HS- and OH-), biothiols (GSH, Cys, Hcy, Me-Cys and lipoic acid), reducing agents (SO2-3 and S2O2-3) and oxidants (H2O2) demonstrated that only HS- is able to induce the appearance of intense emission bands in the 400-520 nm range in the four probes. The selectivity observed was ascribed to a unique hydrogen sulfide-induced hydrolysis of the 2,4-dinitrophenyl ether moiety that yielded the corresponding free highly fluorescent alcohols. The potential detection of intracellular HS- was also studied.
- El Sayed, Sameh,De La Torre, Cristina,Santos-Figueroa, Luis E.,Martinez-Manez, Ramon,Sancenon, Felix,Orzaez, Mar,Costero, Ana M.,Parra, Margarita,Gil, Salvador
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- Effect of cyclodextrin complexation on photo-fries rearrangement of naphthyl esters
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Photolysis of β-cyclodextrin inclusion complexes of 1- and 2-naphthyl esters (acetates and benzoates) in aqueous medium, results in rearrangement to give one isomer of acylnaphthol in excess, whereas the solid state irradiation of the cyclodextrin complexes yields selectively one isomer. In addition, formation of cleavage product is totally suppressed. This remarkable selectivity is attributed to specific modes of the complexation of the esters into the β-CD cavity.
- Banu, Habeeb Shayira,Pitchumani, Kasi,Srinivasan, Chockalingam
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- An efficient approach for the synthesis and antimicrobial evaluation of some new benzocoumarins and related compounds
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A convenient synthetic approach for pharmaceutically important benzocoumarin-based heterocyclic compounds has been studied. β-enaminonitrile has been used for the synthesis of a broad diversity of new benzocoumarins and related compounds over different reaction steps. Various synthetic approaches were used in this research for synthesis of heterocyclic systems such as acid-catalyzed hydrolysis, decarboxylation, deamination, ring opening and ring closure. The molecular structures of the newly synthesized derivatives were established by elemental analyses and spectral data (IR, 1H-NMR, and 13C-NMR). Some of the newly synthesized compounds were explored for their antimicrobial activities.
- Hekal, Mohamed H.,Abu El-Azm, Fatma S. M.,Samir, Sandy S.
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- Regio- and stereochemistry of Na-mediated reductive cleavage of alkyl aryl ethers
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We have investigated the regio-and stereochemistry of the reductive dealkoxylation of alkyl aryl ethers. Chiral non-racemic secondary alcohols were converted into the corresponding m-terphenyl or 2-biphenyl ethers either via inversion of configuration under Mitsunobu reaction conditions or with retention of configuration under SNAr conditions. The successive cleavage of the aromatic C-O bond occurred in the presence of a stoichiometric amount of Na metal in dry tetrahydrofuran at rt with retention of configuration, thus highlighting that the overall inversion or retention of configuration for the whole two-step procedure is dictated by the stereochemistry of the first synthetic step.
- Azzena, Ugo,Carraro, Massimo,Meloni, Claudia,Murgia, Irene,Pisano, Luisa,Pittalis, Mario,Luisi, Renzo,Musio, Biagia,Degennaro, Leonardo
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- MILD CLEAVAGE OF METHOXYMETHYL (MOM) ESTERS WITH TRIMETHYLSILYLBROMIDE
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Trimethylsilyl bromide is an effective reagent for the deprotection of methoxymethyl ethers under mild conditions.
- Hanessian, Stephen,Delorme, Daniel,Dufresne, Yves
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- Synthesis, structures and inclusion properties of tetranaphthalides: New macrocyclic clathrate hosts
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Novel tetranaphthalide host compounds 3 and 4 bearing isomeric naphthalene moieties have been synthesized and their inclusion properties were investigated. These host compounds enclathrated several kinds of ketones, cyclic ethers, amides, sulfoxides and aromatic compounds. The structures of two representative inclusion compounds containing different host molecules and a common guest (dimethyl sulfoxide) were investigated by X-ray diffraction to determine the nature of guest inclusion and to rationalize their distinctly different thermal decomposition profiles.
- Tanaka, Koichi,Hori, Kyosuke,Masumoto, Asuka,Arakawa, Ryuichi,Caira, Mino R.
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- Hydrolytic enzymes conjugated to quantum dots mostly retain whole catalytic activity
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Background Tagging a luminescent quantum dot (QD) with a biological like enzyme (Enz) creates value-added entities like quantum dot-enzyme bioconjugates (QDEnzBio) that find utility as sensors to detect glucose or beacons to track enzymes in vivo. For such applications, it is imperative that the enzyme remains catalytically active while the quantum dot is luminescent in the bioconjugate. A critical feature that dictates this is the quantum dot-enzyme linkage chemistry. Previously such linkages have put constraints on polypeptide chain dynamics or hindered substrate diffusion to active site, seriously undermining enzyme catalytic activity. In this work we address this issue using avidin-biotin linkage chemistry together with a flexible spacer to conjugate enzyme to quantum dot. Methods The catalytic activity of three biotinylated hydrolytic enzymes, namely, hen egg white lysozyme (HEWL), alkaline phosphatase (ALP) and acetylcholinesterase (AChE) was investigated post-conjugation to streptavidin linked quantum dot for multiple substrate concentrations and varying degrees of biotinylation. Results We demonstrate that all enzymes retain full catalytic activity in the quantum dot-enzyme bioconjugates in comparison to biotinylated enzyme alone. However, unlike alkaline phosphatase and acetylcholinesterase, the catalytic activity of hen egg white lysozyme was observed to be increasingly susceptible to ionic strength of medium with rising level of biotinylation. This susceptibility was attributed to arise from depletion of positive charge from lysine amino groups after biotinylation. Conclusions We reasoned that avidin-biotin linkage in the presence of a flexible seven atom spacer between biotin and enzyme poses no constraints to enzyme structure/dynamics enabling retention of full enzyme activity. General significance Overall our results demonstrate for the first time that streptavidin-biotin chemistry can yield quantum dot enzyme bioconjugates that retain full catalytic activity as native enzyme.
- Iyer, Aditya,Chandra, Anil,Swaminathan, Rajaram
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- Decarbethoxylative Arylation Employing Arynes: A Metal-Free Pathway to Arylfluoroamides
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An efficient, metal-free decarbethoxylative arylation protocol for the synthesis of α-aryl-α-fluoroamides from fluoromalonamates, under ambient reaction conditions using aryne as an electrophilic arylating agent, is reported. This decarbethoxylative arylation proceeds under mild conditions and provides a practical and effective entry to a wide range of α-aryl-α-fluoroacetamides. Interestingly, the use of the tert-butyl ester of fluoromalonamate prevented the otherwise rapid decarboxylation step, affording the arylated fluoromalonamate in moderate yield.
- Gupta, Ekta,Kant, Ruchir,Mohanan, Kishor
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- Nucleophilic Hydroxylation in Water Media Promoted by a Hexa-Ethylene Glycol-Bridged Dicationic Ionic Liquid
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Hexaethylene glycol bis(3-hexaethylene glycol imidazolium) dimesylate ionic liquid (hexaEG-DHIM) was designed and prepared as a highly efficient promoter for the nucleophilic hydroxylation of alkyl halides to the corresponding alcohol products in neat water media. It was observed that hexaEG-DHIM promoter enhanced the nucleophilicity of water significantly in the reaction. In addition, the hexaEG-DHIM could be reused several times without loss of activity. Moreover, the hydroxylation reactions of base-sensitive and/or polar alkyl halide substrates proceeded highly chemoselectively in excellent yields.
- Jadhav, Vinod H.,Kim, Jin Gwan,Jeong, Hyeon Jin,Kim, Dong Wook
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- Cationic reverse micelles create water with super hydrogen-bond-donor capacity for enzymatic catalysis: Hydrolysis of 2-naphthyl acetate by α-Chymotrypsin
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Reverse micelles (RMs) are very good nanoreactors because they can create a unique microenvironment for carrying out a variety of chemical and biochemical reactions. The aim of the present work is to determine the influence of different RM interfaces on the hydrolysis of 2-naphthyl acetate (2NA) by α-chymotrypsin (α-CT). The reaction was studied in water/benzyl-nhexadecyldimethylammonium chloride (BHDC)/benzene RMs and, its efficiency compared with that observed in pure water and in sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) RMs. Thus, the hydrolysis rates of 2-NA catalyzed by α-CT were determined by spectroscopic measurements. In addition, the method used allows the joint evaluation of the substrate partition constant Kp between the organic and the micellar pseudophase and the kinetic parameters: catalytic rate constant kcat, and the Michaelis constant KM of the enzymatic reaction. The effect of the surfactant concentration on the kinetics parameters was determined at constant W 0= [H2O]/[surfactant], and the variation of W0 with surfactant constant concentration was investigated. The results show that the classical Michaelis-Menten mechanism is valid for α-CT in all of the RMs systerns studied and that the reaction takes place at both RM interfaces. Moreover, the catalytic efficiency values kcat/KM obtained in the RMs systems are higher than that reported in water. Furthermore, there is a remarkable increase in α-CT efficiency in the cationic RMs in comparison with the anionic system, presumably due to the unique water properties found in these confined media. The results show that in cationic RMs the hydrogen-bond donor capacity of water is enhanced due to its interaction with the cationic interface. Hence, entrapped water can be converted into "super-water" for the enzymatic reaction studied in this work.
- Moyano, Fernando,Falcone, R. Falcone,Mejuto,Silber, Juana J.,Correa, N. Mariano
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- HCl/DMF for enhanced chemoselectivity in catalytic hydrogenolysis reactions
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An improved, chemoselective hydrogenolysis method has been developed. By employing a solvent-acid combination (i.e., DMF-aq HCl) we were able to favor debenzylation rather than aromatic hydrogenation and acid-mediated bond cleavage which are the two main drawbacks of these reactions. The generality of the method, which was primarily developed as a solution to a carbohydrate problem, is shown by the successful hydrogenolysis of 1,8-naphthalide, a previously unsolved problem.
- Ochocinska, Agata,Siegbahn, Anna,Ellervik, Ulf
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- A novel application of Hβ-zeolite in catalytic dehalogenation of halophenols
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A new application of Hβ-zeolite for debromination of bromophenols and deiodination of iodophenols is presented in this note. The heterogeneous catalyst can be recovered and recycled effectively for subsequent reactions. The catalyst was found ineffective for similar action on chlorophenols.
- Adimurthy, Subbarayappa,Ramachandraiah, Gadde,Bedekar, Ashutosh V.
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- Functional Analyses of House Fly Carboxylesterases Involved in Insecticide Resistance
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Carboxylesterase-mediated metabolism is one of major mechanisms involved in insecticide resistance. Our previous study has identified multiple carboxylesterase genes with their expression levels were significantly upregulated in pyrethroid resistant house flies. To further explore their metabolic functions, we used insect Spodoptera frugiperda (Sf9) cells to express these carboxylesterases in vitro and measure their hydrolytic activities toward esterase substrates. Our results indicated that these carboxylesterases can efficiently hydrolyze α-naphthyl acetate rather than β- naphthyl acetate. A cell based MTT cytotoxicity assay indicated that carboxylesterase-expressing cells show enhanced tolerance to permethrin, suggesting important roles of these carboxylesterases in metabolizing permethrin and thereby protecting cells from permethrin treatments. The metabolic functions of carboxylesterases were further verified by conducting in vitro metabolism studies toward permethrin and its potential metabolites 3-phenoxybenzyl alcohol and 3-phenoxybenzaldehyde, which not only suggested the potential metabolic pathway of permethrin in insects, but also important roles of these candidate carboxylesterases in metabolizing permethrin and conferring resistance in house flies. Homology modeling and docking were finally conducted to reflect interactions between permethrin ligand and carboxylesterase proteins, visually confirming the metabolic functions of carboxylesterases to insecticides in house flies.
- Feng, Xuechun,Liu, Nannan
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- Pharmacokinetics of 2-naphthol following intrapericardial administration, and formation of 2-naphthyl-β-D-glucoside and 2-naphthyl sulphate in the American lobster, Homarus americanus
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1. Following a 0.25-mg/kg intrapericardial dose of the phenolic compound, 2-naphthol, to the American lobster, Homarus americanus, a two-compartment model best described the disposition of parent [14C]-2-naphthol in the haemolymph. Male and female lobsters had similar α-phase half lives of 26 ± 19 min (mean ± SD, n = 4) and 29 ± 15 min respectively. The β-phase half lives were significantly longer in males, 63.9 ± 30.9 h, than in females, 30.6 ± 6.8 h (P -1 x kg-1 and was higher than that of males, 11.1 ± 5.9 ml x h-1 x kg-1 (p 99% bound to haemolymph proteins at 1 min find > 90% bound at 1 day after the dose, indicating that both 2-naphthol and 2-naphthyl-β-D-glucoside were highly protein bound. 4. 2-Naphthyl-β-D-glucoside was slowly eliminated from haemolymph in both males and females, with elimination half lives of 34-78 h. 2-Naphthyl-β-D-glucoside was the major metabolite in urine samples collected at 5 days after the dose. Hepatopancreas and antennal gland contained glucosidase activities, and the long half life of 2-naphthyl-β-D-glucoside could be explained by conjugation-deconjugation cycling. 5. 2-Naphthyl sulphate was eliminated from haemolymph with a half-life 10 h and was excreted in urine.
- Li,James
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- The reduction of graphene oxide with hydrazine: elucidating its reductive capability based on a reaction-model approach
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We have performed an experimental investigation on the effects of hydrazine treatment on graphene oxide via a reaction-model approach. Hydrazine was reacted with small conjugated aromatic compounds containing various oxygen functional groups to mimic the structure of graphene oxide. The hydroxyl and carboxylic groups were not readily removed while carbonyl groups reacted with hydrazine to form the corresponding hydrazone complexes. In the presence of adjacent hydroxyl groups, carboxyl groups underwent thermal decarboxylation.
- Chua, Chun Kiang,Pumera, Martin
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- PHOTOCHEMICAL REACTIONS OF NAPHTHYL-VINYL NON-CONJUGATED BICHROMOPHORIC SYSTEMS
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2-(1-Naphthyl)ethyl vinyl ether undergoes intramolecular 1,2-photocycloaddition whereas the 2-naphthyl isomer yields a product reflecting dimerisation and loss of the elements of acetylene: consistent with such diverse photochemistry, the addition of 2,3-dihydropyran to naphthalene produces only the 1,2-, 1',2'-regioisomer.
- Kashoulis, Annoula,Gilbert, Andrew,Ellis-Davies, Graham
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- Mechanistic Insights into Hydrogen Evolution by Photocatalytic Reforming of Naphthalene
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Heterogeneous photocatalysis has been widely considered, among other applications, for environmental remediation and hydrogen production. While these applications have been traditionally seen as well-separated areas, recent examples have highlighted the possibility of coupling them. Here, we demonstrate the simultaneous production of H2 and naphthalene removal from aqueous solutions with (unoptimized) photonic efficiencies of 0.97 and 0.33percent, respectively, over Pt-TiO2 under simulated sunlight. Photocatalytic and spin-trapping experiments in the presence of a hydroxyl radical and hole scavengers evinced that only the photogenerated holes play a significant role in the oxidation of naphthalene. Isotopic labeling analyses showed that the evolved H2 isotopologues match those of the solvent and that deuterated water (but not deuterated naphthalene) decreases the reaction rate, suggesting its involvement in the rate-determining step. Moreover, the use of Ti18O2 does not lead to the significant formation of 18O-enriched CO2, suggesting that water is the source of the oxygen atoms. Ultimately, by considering the stable and transient reaction intermediates, we propose a plausible reaction pathway. Our work illustrates that environmental remediation can be effectively coupled to solar fuel production, providing a double purpose to photocatalytic reactions, while the mechanistic insights will be of use for the further development of this strategy.
- Al-Madanat, Osama,Alsalka, Yamen,Bahnemann, Detlef W.,Curti, Mariano,Dillert, Ralf
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- Conversion of 1-tetralone over HY zeolite: An indicator of the extent of hydrogen transfer
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The conversion of pure 1-tetralone and its mixtures with n-decane, decalin, tetralin, or 1,5-dimethyl tetralin (DMT) has been investigated over HY zeolite. The dominant reactions undergone by 1-tetralone are the dehydrogenation to 1-naphthol and the subsequent isomerization to 2-naphthol. In the presence of hydrocarbons, the hydrogen transfer/dehydration of naphthols is accelerated, and naphthalene is formed in different amounts, depending on the nature of the co-fed hydrocarbon. In this contribution, it is demonstrated how the product distribution from the tetralone conversion can be used as an indicator of the hydrogen transfer ability of a particular hydrocarbon, or mixture of hydrocarbons. The relative order of hydrogen transfer ability of the various hydrogen donating compounds, as inferred from the naphthalene-to-naphthol product ratio, is DMT > tetralin ≈ decalin > n-decane. This trend agrees well with the hydride dissociation energy of individual donors calculated by DFT.
- Prasomsri, Teerawit,Galiasso Tailleur, Roberto E.,Alvarez, Walter E.,Sooknoi, Tawan,Resasco, Daniel E.
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- Formation of naphthalene hydrates in the enzymatic conversion of 1,2-dihydronaphthalene by two fungal peroxygenases and subsequent naphthalene formation
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The formation of naphthalene hydrates (i.e. 1- and 2-hydroxy-1,2- dihydronaphthalene) displays a new activity (besides epoxidation) in the enzymatic transformation of 1,2-dihydronaphthalene by two fungal unspecific peroxygenases (UPOs) accounting for 16-19% of the overall turnover. These arene hydrates decayed into naphthalene that in turn was converted by UPOs into naphthols. The oxygen transferred during hydroxylation was shown to derive from hydrogen peroxide proving a true peroxygenation reaction.
- Kluge, Martin,Ullrich, Rene,Scheibner, Katrin,Hofrichter, Martin
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- Enzymatic Reaction in Water-in-Oil Microemulsions. Part 2. - Rate of Hydrolysis of a Hydrophobic Substrate, 2-Naphthyl Acetate
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The catalytic hydrolysis rates of a hydrophobic substrate, 2-naphthyl acetate (NA), have been measured both in aqueous solution and in water-in-oil microemulsions (ME) formed by di(2-ethylhexyl)sodium sulfosuccinate (AOT) in heptane.The catalysts used were lipase, α-chymotrypsin and imidazole.The dependence of WO = OV/OV at a constant OV and of OV at a constant WO on the overall rate constants were discussed in terms of a reaction model.The reaction model includes three parameters, the distribution constants of NA and the catalysts and the rate constant of the local reaction field.The distribution constant of NA was evaluated by measurements of the distribution of NA between the ME in the Winsor II region and the aqueous phase, but that of catalysts was treated as a fitting parameter.It is suggested that the reactions with these catalysts proceeds at the interfacial region of ME.For the imidazole-catalysed reaction, if the imidazole exists preferentially at the interface, the rate constant is independent of WO, but the values was 0.2 times that in the aqueous phase.Superactivity of lipase was observed, that is the turnover number in ME was greater than that in the aqueous phase.However, as the Michaelis constant was also large, the rate constant (kCAT/km) in ME was smaller than that in the aqueous phase.The rate constant increased as WO increased.The dependence was caused by the conformation change of lipase due to the interaction of AOT molecules.The rate constants for both imidazole and lipase decreased with increase in at constant WO, which might be caused by the change in the structure of ME.The turnover number for α-chymotrypsin at the interface was lower than that in the aqueous phase and approached the values in the aqueous phase as WO and increased.However, the Michaelis constant decreased with increase in WO and approached a constant value, which was 25 times that in the aqueous phase.
- Miyake, Yoshikazu,Owari, Takuya,Ishiga, Fumio,Teramoto, Masaaki
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- Novel spectral manipulations for determinations of Tolnaftate along with related toxic compounds: Drug profiling and a comparative study
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A comparative study using novel quadruple divisor and mean centering of ratio spectra spectrophotometric methods was developed for resolution of five- component mixture of Tolnaftate, β-naphthol (Tolnaftate alkaline degradation product and its toxic impurity), methyl(m-tolyl)carbamic acid (Tolnaftate alkaline degradation product), N-methyl-m-toluidine (Tolnaftate toxic impurity) and methyl paraben (as a preservative). For the novel quadruple divisor method, each component in the quinary mixture was determined by dividing the quinary mixture spectrum by a sum of standard spectrum of equal concentration of the other four components as a quadruple divisor. First derivative of each ratio spectra was then obtained which allowed selective determination of each component without interference from other components in the mixture. The second method was mean centering of ratio spectra that depended on utilizing the mean centered ratio spectra in four successive steps leading to enhancement of the signal to noise ratio. The absorption spectra of the five studied components were recorded in the wavelength range of 210–350 nm. The mean centered fourth ratio spectra amplitudes for each component were used for its determination. The developed methods were successfully applied for determination of laboratory prepared quinary mixtures to ensure method's specificity, then, were further applied on Tinea Cure cream where no interference from excipients. For the first time, Tolnaftate was determined along with its toxic impurity; β-naphthol, that could be absorbed by the skin, causing systemic toxic effects, unlike Tolnaftate that poorly absorbed, indicating the significance of this work. The proposed methods were statistically compared with each other and with the reference method. Furthermore, ICH guidelines were followed for their validation.
- Emam, Raghda A.,Abdelrahman, Maha M.,Abdelaleem, Eglal A.,Ali, Nouruddin W.
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- Oxyfunctionalization of Hydrocarbons. 17. Acid-Dependent High Regioselectivity Hydroxylation of Naphthalene with Hydrogen Peroxide Giving 1- or 2-Naphthol
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The acid-catalyzed hydroxylation of naphthalene with 90percent hydrogen peroxide was investigated.Regioselectivity of the reaction depends on the acidity of the system and the solvent used.In anhydrous hydrogen fluoride or 70percent HF-30percent pyridine solution at -10 to +20 deg C 1-naphthol is the product formed in > 98percent selectivity.In contrast, 2-naphthol is obtained in hydroxylation in superacid (HF-BF3, HF-SbF5, HF-TaF5, FSO3H-SbF5) solution at -60 to -78 deg C in > 98percent selectivity.When 1-naphthol reacted under the latter conditions 1,5- and 1,7-dihydroxynaphthalene were obtained, while 2-naphthol gave 1,6-dihydroxynaphthalene (along with only minor amounts of 1,7-dihydroxynapthtalene).The mechanism of the reactions is discussed, contrasting electrophilic hydroxylation of naphthalene, giving predominantly 1-substitution, with reaction of protonated naphthalenes (i.e., naphthtalenium ions) with hydrogen peroxide.
- Olah, George A.,Keumi, Takashi,Lecoq, Jean Claud,Fung, Alexander P.,Olah, Judith A.
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- Mechanistic imperatives for catalysis of aldol addition reactions: Partitioning of the enolate intermediate between reaction with bronsted acids and the carbonyl group
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The lyoxide ion catalyzed intramolecular aldol addition reaction of 2- (2-oxopropyl)benzaldehyde (1) to give the aldol adduct 3 proceeds via essentially irreversible formation of the acetone-like enolate intermediate 2, because reprotonation of 2 by a solvent of H2O or D2O (k(HOH) or k(DOD)) is much slower than intramolecular addition of the enolate to the carbonyl group (k(c)). The aldol addition reaction of 1 catalyzed by high concentrations of 3-substituted quinuclidine buffers proceeds via reversible deprotonation of 1 to give the enolate 2, and rate-determining addition of the enolate to the carbonyl group. A rate constant ratio of k(c)/k(HOH) = 35 was determined for partitioning of the enolate 2 between intramolecular addition to the carbonyl group and protonation by solvent water. The corresponding ratios k(BH)/k(c) (M-1) for the protonation of 2 by Bronsted buffer acids and intramolecular aldol addition increase from 7 to 450 as the acidity of the buffer acid is increased from pK(BH) = 11.5 to 7.5. The data show that the electrophilic reactivity of the benzaldehyde carbonyl group toward intramolecular addition of the enolate 2 is the same as that of a hypothetical tertiary ammonium cation of pK(BH) = 13.3. The Marcus intrinsic barrier for addition of the enolate 2 to the carbonyl group is unexpectedly small, which suggests that the transition state for this reaction is stabilized by interactions between the soft-soft acid-base pair. The relevance of this work to chemical and enzymatic catalysis of aldol condensation reactions is discussed.
- Richard, John P.,Nagorski
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- Selective Reductive Cleavage of Arenocrown Ethers by Alkali Metals in THF
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Alkali metal solutions in tetrahydrofuran containing the arenocrown ethers naphtho-15-crown-5, benzo-15-crown-5, and benzo-18-crown-6 were investigated using 39K NMR, ESR, and GC-MS techniques.The cleavage of carbon-oxygen bonds in the crown ethers studied is discussed.
- Sokol, Maria,Kowalczuk, Marek,Grobelny, Zbigniew,Janeczek, Henryk,Jedlinski, Zbigniew,et al.
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- UEBER DIE REAKTION VON α- UND β-TETRALON MIT KALIUMSUPEROXID
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The reaction of α- and β-tetralone with potassium superoxide is described.In addition to 2-hydroxy-1,4-naphthoquinone α-naphthol is formed from α-tetralone and β-naphthol and 2-carboxy-benzenepropionic acid from β-tetralone.
- Lissel, Manfred
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- Two channels of electron transfer observed for the reaction of n-butyl chloride parent radical cations with naphthols and hydroxybiphenyls
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Pulse radiolysis of naphthols (NpOH) and hydroxybiphenyls (ByOH) in n-butyl chloride (BuCl) at room temperature exhibits electron transfer at a bimolecular rate constant of (1.0-2.8) × 1010 dm3 mol-1 s-1. The experiments reveal the direct formation of two types of transients: phenol type radical cations (NpOH?+, ByOH?+) and phenoxyl type radicals (NpO?, ByO?). This is explained by a mechanism involving two different electron-transfer channels. The solute radical cations exhibit two optical absorption bands in the 570-650 and 360-460 nm regions and undergo electron transfer with triethylamine and proton transfer with ethanol with bimolecular rate constants of (4-12) × 109 and (3-6) × 108 dm3 mol-1 s-1, respectively. NpO? and ByO? have relatively long lifetimes and show absorption bands in the 340-400 and 470-540 nm regions. By way of comparison, these phenoxyl type radicals are separately generated by pulse radiolysis in aqueous alkaline solution containing sodium azide, i.e., by oxidation of the solutes with N3? radicals. Under these conditions, the phenoxyl radicals decay by second-order kinetics with 2k = (1.2-4.5) × 108 dm3 mol-1 s-1. The various modes of formation and decay of the phenolic radical cations are analyzed over a wide range of dose rate and solute concentrations. In comparison to radical cations of one-ring phenols, the increased stability of NpOH?+ and ByOH?+ is explained by the delocalization of the positive charge over the whole aromatic system, a postulate supported by open-shell quantum chemical calulations.
- Mohan,Hermann,Naumov,Mittal,Brede
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- Acid-Catalyzed Versus Thermally Induced C1-C1′ Bond Cleavage in 1,1′-Bi-2-naphthol: An Experimental and Theoretical Study
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Experiments show that 1,1′-bi-2-naphthol (BINOL) undergoes facile C1-C1′ bond cleavage under action of triflic acid at temperatures above 0 °C to give mainly 2-naphthol along with oligomeric material. CASSCF and MRMP//CASSCF computations have demonstrated unambiguously that this unusual mode of scission of the biaryl bond can occur in the C1,C1′-diprotonated form of BINOL via a mechanism involving homolytic cleavage prompted by the intramolecular electrostatic repulsion. These findings also provide insights into the mechanism of a comparatively easy thermal cleavage of BINOL, implying the intermediacy of its neutral diketo form.
- Genaev, Alexander M.,Shchegoleva, Lyudmila N.,Salnikov, George E.,Shernyukov, Andrey V.,Shundrin, Leonid A.,Shundrina, Inna K.,Zhu, Zhongwei,Koltunov, Konstantin Yu.
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- Coordination of manganese porphyrins on amino-functionalized MCM-41 for heterogeneous catalysis of naphthalene hydroxylation
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The different amounts of [5,10,15,20-tetrakis-(pentafluorophenyl)porphyrin] manganese chloride (TF20PPMnCl) were immobilized on amino-functionalized MCM-41 for catalysis of the hydroxylation of naphthalene. The samples were characterized by X-ray powder diffraction, N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, diffuse reflectance ultraviolet-visible spectroscopy, thermogravimetric and differential scanning calorimetry, and inductively coupled plasma mass spectrometry. The results indicated that the manganese porphyrins were axially coordinated on amino-functionalized MCM-41. The prepared samples showed remarkable catalytic activity in the hydroxylation of naphthalene with meta-chloroperbenzoic acid as the oxidant. The catalyst could be reused several times without loss of its activity.
- Yang, Fu,Gao, Shuying,Xiong, Cuirong,Wang, Haiqing,Chen, Jin,Kong, Yan
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- Atropselective hydrolysis of chiral BiNoL-phosphate esters catalyzed by the phosphotriesterase from Sphingobium sp. TCM1
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The phosphotriesterase from Sphingobium sp. TCM1 (Sb-PTE) is notable for its ability to hydrolyze a broad spectrum of organophosphate triesters, including organophosphorus flame retardants and plasticizers such as triphenyl phosphate and tris(2-chloroethyl) phosphate that are not substrates for other enzymes. This enzyme is also capable of hydrolyzing any one of the three ester groups attached to the central phosphorus core. The enantiomeric isomers of 1,1′-bi-2-naphthol (BINOL) have become among the most widely used chiral auxiliaries for the chemical synthesis of chiral carbon centers. PTE was tested for its ability to hydrolyze a series of biaryl phosphate esters, including mono- and bis-phosphorylated BINOL derivatives and cyclic phosphate triesters. Sb-PTE was shown to be able to catalyze the hydrolysis of the chiral phosphate triesters with significant stereoselectivity. The catalytic efficiency, kcat/Km, of Sb-PTE toward the test phosphate triesters ranged from ～10 to 105 M?1 s?1. The product ratios and stereoselectivities were determined for four pairs of phosphorylated BINOL derivatives.
- Xiang, Dao Feng,Narindoshvili, Tamari,Raushel, Frank M.
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- Bacterial Oxidation of Naphtharene to 1-Naphthol
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The oxidation of naphtharene in a liquid culture was carried out in the presence of Bacillus cereus. 1-Naphthol was obtained in 11-20percent yield and the selectivity of 65-77percent at 28 deg C and pH 7.0 after 12-24 h.The ratio of 1-naphthol to 2-naphthol was 94:6.
- Inoue, Masami,Inoue, Tomoni,Okami, Mituaki,Sayama, Michio,Hirai, Yoshiro
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- Effect of Confinement on the Properties of Sequestered Mixed Polar Solvents: Enzymatic Catalysis in Nonaqueous 1,4-Bis-2-ethylhexylsulfosuccinate Reverse Micelles
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The influence of different glycerol, N,N-dimethylformamide (DMF) and water mixtures encapsulated in 1,4-bis-2-ethylhexylsulfosuccinate (AOT)/n-heptane reverse micelles (RMs) on the enzymatic hydrolysis of 2-naphthyl acetate by α-chymotrypsin is demonstrated. In the case of the mixtures with DMF and protic solvents it has been previously shown, using absorption, emission and dynamic light-scattering techniques, that solvents are segregated inside the polar core of the RMs. Protic solvents anchor to the AOT, whereas DMF locates to the polar core of the aggregate. Thus, DMF not only helps to solubilize the hydrophobic substrate, increasing its effective concentrations but surprisingly, it does not affect the enzyme activity. The importance of ensuring the presence of RMs, encapsulation of the polar solvents and the corrections by substrate partitioning in order to obtain reliable conclusions is highlighted. Moreover, the effect of a constrained environment on solvent–solvent interactions in homogenous media and its impact on the use of RMs as nanoreactors is stressed.
- Durantini, Andres M.,Falcone, R. Dario,Silber, Juana J.,Correa, N. Mariano
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- Mn(III) active site in hydrotalcite efficiently catalyzes the oxidation of alkylarenes with molecular oxygen
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Developing efficient heterogeneous catalytic systems based on easily available materials and molecular oxygen for the selective oxidation of alkylarenes is highly desirable. In the present research, NiMn hydrotalcite (Ni2Mn-LDH) has been found as an efficient catalyst in the oxidation of alkylarenes using molecular oxygen as the sole oxidant without any additive. Impressive catalytic performance, excellent stability and recyclability, broad applicable scope and practical potential for the catalytic system have been observed. Mn3+ species was proposed to be the efficient active site, and Ni2+ played an important role in stabilizing the Mn3+ species in the hydrotalcite structure. The kinetic study showed that the aerobic oxidation of diphenylmethane is a first-order reaction over Ni2Mn-LDH with the activation energy (Ea) and pre-exponential factor (A0) being 85.7 kJ mol?1 and 1.8 × 109 min?1, respectively. The Gibbs free energy (ΔG≠) was determined to be -10.4 kJ mol-1 K-1 for the oxidation based on Eyring-Polanyi equation, indicating the reaction is exergonic. The mechanism study indicated that the reaction proceeded through both radical and carbocation intermediates. The two species were then trapped by molecular oxygen and H2O or hydroxyl species, respectively, to yield the corresponding products. The present research might provide information for constructing highly efficient and stable active site for the catalytic aerobic oxidation based on available and economic material.
- Wang, Anwei,Zhou, WeiYou,Sun, Zhonghua,Zhang, Zhong,Zhang, Zhihui,He, MingYang,Chen, Qun
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- Biocatalytic Cross-Coupling of Aryl Halides with a Genetically Engineered Photosensitizer Artificial Dehalogenase
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Devising artificial photoenzymes for abiological bond-forming reactions is of high synthetic value but also a tremendous challenge. Disclosed herein is the first photobiocatalytic cross-coupling of aryl halides enabled by a designer artificial dehalogenase, which features a genetically encoded benzophenone chromophore and site-specifically modified synthetic NiII(bpy) cofactor with tunable proximity to streamline the dual catalysis. Transient absorption studies suggest the likelihood of energy transfer activation in the elementary organometallic event. This design strategy is viable to significantly expand the catalytic repertoire of artificial photoenzymes for useful organic transformations.
- Fu, Yu,Huang, Jian,Wu, Yuzhou,Liu, Xiaohong,Zhong, Fangrui,Wang, Jiangyun
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supporting information
p. 617 - 622
(2021/02/03)
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- Palladium-catalyzed ortho-C-H hydroxylation of benzoic acids
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A simple Pd(OAc)2 catalyzed ortho-hydroxylation of benzoic acids using TBHP as the sole oxidant has been explored. This protocol features relatively broad substrate scope and operational simplicity. The compatibility of ortho-substituted substrates is an effective complement to the previous ortho-hydroxylation reaction.
- Luo, Feihua,He, Shuhua,Gou, Quan,Chen, Jinyang,Zhang, mingzhong
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- Ligand compound for copper catalyzed aryl halide coupling reaction, catalytic system and coupling reaction
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The invention provides a ligand compound capable of being used for copper catalyzed aryl halide coupling reaction, the ligand compound is a three-class compound containing a 2-(substituted or non-substituted) aminopyridine nitrogen-oxygen group, and the invention also provides a catalytic system for the aryl halide coupling reaction. Thecatalytic system comprises a copper catalyst, a compound containing a 2-(substituted or non-substituted) aminopyridine nitrogen-oxygen group adopted as a ligand, alkali and a solvent, and meanwhile, the invention also provides a system for the aryl halide coupling reaction adopting the catalyst system. The compound containing the 2-(substituted or non-substituted) aminopyridine nitrogen oxygen group can be used as the ligand for the copper catalyzed aryl chloride coupling reaction, and the ligand is stable under a strong alkaline condition and can well maintain catalytic activity when being used for the copper-catalyzed aryl chloride coupling reaction. In addition, the copper catalyst adopting the compound as the ligand can particularly effectively promote coupling of copper catalyzed aryl chloride and various nucleophilic reagents which are difficult to generate under conventional conditions, C-N, C-O and C-S bonds are generated, and numerous useful small molecule compounds are synthesized. Therefore, the aryl halide coupling reaction has a very good large-scale application prospect by adopting the copper catalysis system of the ligand.
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Paragraph 0152-0159
(2021/05/29)
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- A mild and practical method for deprotection of aryl methyl/benzyl/allyl ethers with HPPh2andtBuOK
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A general method for the demethylation, debenzylation, and deallylation of aryl ethers using HPPh2andtBuOK is reported. The reaction features mild and metal-free reaction conditions, broad substrate scope, good functional group compatibility, and high chemical selectivity towards aryl ethers over aliphatic structures. Notably, this approach is competent to selectively deprotect the allyl or benzyl group, making it a general and practical method in organic synthesis.
- Pan, Wenjing,Li, Chenchen,Zhu, Haoyin,Li, Fangfang,Li, Tao,Zhao, Wanxiang
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p. 7633 - 7640
(2021/09/22)
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- Photocatalytic Reductive C-O Bond Cleavage of Alkyl Aryl Ethers by Using Carbazole Catalysts with Cesium Carbonate
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Methods to activate the relatively stable ether C-O bonds and convert them to other functional groups are desirable. One-electron reduction of ethers is a potentially promising route to cleave the C-O bond. However, owing to the highly negative redox potential of alkyl aryl ethers (Ered -2.6 V vs SCE), this mode of ether C-O bond activation is challenging. Herein, we report the visible-light-induced photocatalytic cleavage of the alkyl aryl ether C-O bond using a carbazole-based organic photocatalyst (PC). Both benzylic and non-benzylic aryl ethers underwent C-O bond cleavage to form the corresponding phenol products. Addition of Cs2CO3 was beneficial, especially in reactions using a N-H carbazole PC. The reaction was proposed to occur via single-electron transfer (SET) from the excited-state carbazole to the substrate ether. Interaction of the N-H carbazole PC with Cs2CO3 via hydrogen bonding exists, which enables a deprotonation-assisted electron-transfer mechanism to operate. In addition, the Lewis acidic Cs cation interacts with the substrate alkyl aryl ether to activate it as an electron acceptor. The high reducing ability of the carbazole combined with the beneficial effects of Cs2CO3 made this otherwise formidable SET event possible.
- Yabuta, Tatsushi,Hayashi, Masahiko,Matsubara, Ryosuke
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p. 2545 - 2555
(2021/02/01)
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- Electrochemical phenothiazination of naphthylamines and its application in photocatalysis
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N-Phenylphenothiazine as an inexpensive, highly reductive and oxygen tolerant organophotocatalyst has exhibited potential in various challenging photochemical transformations. Here we report a general and straightforward method to access structurally diverse N-phenylphenothiazine derivatives by means of a novel electrochemical tool. The introduction of a 2-naphthylamine moiety with an extended π-system and an amine group led to the variation of spectral characterization. Photochemical verification experiments demonstrated that the formed N-arylation products with good efficacy and chemo/site-control displayed competitive catalytic activity in challenging transformations. This journal is
- Chen, Song,Li, Ya-Nan,Xiang, Shao-Hua,Li, Shaoyu,Tan, Bin
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supporting information
p. 8512 - 8515
(2021/08/31)
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- Me3SI-promoted chemoselective deacetylation: a general and mild protocol
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A Me3SI-mediated simple and efficient protocol for the chemoselective deprotection of acetyl groups has been developedviaemploying KMnO4as an additive. This chemoselective deacetylation is amenable to a wide range of substrates, tolerating diverse and sensitive functional groups in carbohydrates, amino acids, natural products, heterocycles, and general scaffolds. The protocol is attractive because it uses an environmentally benign reagent system to perform quantitative and clean transformations under ambient conditions.
- Gurawa, Aakanksha,Kashyap, Sudhir,Kumar, Manoj
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p. 19310 - 19315
(2021/06/03)
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- Well-defined Cp*Co(III)-catalyzed Hydrogenation of Carbonates and Polycarbonates
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We herein report the catalytic hydrogenation of carbonates and polycarbonates into their corresponding diols/alcohols using well-defined, air-stable, high-valent cobalt complexes. Several novel Cp*Co(III) complexes bearing N,O-chelation were isolated for the first time and structurally characterized by various spectroscopic techniques including single crystal X-ray crystallography. These novel Co(III) complexes have shown excellent catalytic activity to produce value added diols/alcohols from carbonate and polycarbonates through hydrogenation using molecular hydrogen as sole reductant or iPrOH as transfer hydrogenation source. To demonstrate the developed methodology's practical applicability, we have recycled the bisphenol A monomer from compact disc (CD) through hydrogenation under the established reaction conditions using phosphine-free, earth-abundant, air- and moisture-stable high-valent cobalt catalysts.
- Dahiya, Pardeep,Gangwar, Manoj Kumar,Sundararaju, Basker
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p. 934 - 939
(2020/12/15)
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- Nickel-catalyzed deallylation of aryl allyl ethers with hydrosilanes
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An efficient and mild catalytic deallylation method of aryl allyl ethers is developed, with commercially available Ni(COD)2 as catalyst precursor, simple substituted bipyridine as ligand and air-stable hydrosilanes. The process is compatible with a variety of functional groups and the desired phenol products can be obtained with excellent yields and selectivity. Besides, by detection or isolation of key intermediates, mechanism studies confirm that the deallylation undergoes η3-allylnickel intermediate pathway.
- Ding, Guangni,Fan, Sijie,Wang, Jingyang,Wang, Yu,Wu, Xiaoyu,Xie, Xiaomin,Yang, Liqun,Zhang, Zhaoguo
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supporting information
(2021/09/28)
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- PREPARING METHODE FOR NAPHTHOL
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The present invention provides a method for producing naphthol by oxidizing naphthalene and an oxidizing agent in the presence of a catalyst. According to the present invention, naphthol can be produced in a single process of direct oxidation of naphthalene, and the yield and selectivity of naphthalene can be improved by controlling process variables such as the molar ratio of the oxidizing agent and naphthalene, catalyst input amount, and reaction time.
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Paragraph 0032-0048
(2021/01/28)
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- Decarboxylative Hydroxylation of Benzoic Acids
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Herein, we report the first decarboxylative hydroxylation to synthesize phenols from benzoic acids at 35 °C via photoinduced ligand-to-metal charge transfer (LMCT)-enabled radical decarboxylative carbometalation. The aromatic decarboxylative hydroxylation is synthetically promising due to its mild conditions, broad substrate scope, and late-stage applications.
- Ritter, Tobias,Su, Wanqi,Xu, Peng
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p. 24012 - 24017
(2021/10/06)
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- Highly recyclable Ti0.97Ni0.03O1.97catalyst coated on cordierite monolith for efficient transformation of arylboronic acids to phenols and reduction of 4-nitrophenol
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A stable Ni2+substituted TiO2catalyst (Ti0.97Ni0.03O1.97) has been synthesized by a solution combustion method with an average crystallite size of 7.5 nm. Ti1?xNixO2?x(x= 0.01-0.06) crystallizes in the TiO2anatase structure with Ni2+substituted in Ti4+ion sites and Ni taking a nearly square planar geometry. This catalyst is found to be highly active in the transformation of diverse arylboronic acids to the corresponding phenols. The catalyst coated cordierite monolith can even be recycled for up to 20 cycles with a cumulative TOF of 1.8 × 105h?1. In scale-up reactions, various phenols are synthesized by employing a single cordierite monolith. It also shows high performance in the reduction of 4-nitrophenol.
- Hegde, M. S.,Prasanna,Usha, K. M.
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supporting information
p. 14223 - 14234
(2021/10/25)
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- Isotruxene-based porous polymers as efficient and recyclable photocatalysts for visible-light induced metal-free oxidative organic transformations
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Two new isotruxene-based porous polymers were prepared and demonstrated to be highly efficient, metal-free heterogeneous photocatalysts for oxidative transformations using air as the mild oxidant under visible-light irradiation. Both catalysts show excellent recyclability. In addition, the reactions can be performed in water, further indicating the greenness of this method. This journal is
- Zhang, Haowen,Zhang, Xiao,Zheng, Ying,Zhou, Cen
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supporting information
p. 8878 - 8885
(2021/11/27)
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- Highly efficient, recyclable and alternative method of synthesizing phenols from phenylboronic acids using non-endangered metal: Samarium oxide
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Oxidation of phenylboronic acid to phenol is one of the important industrial processes and it is generally employed in the plastic, explosive and drug manufacturing industries. Over the past decades, numerous efficient methods have been described for the generation of phenols from phenylboronic acids in the presence of oxidant. However, these methods suffered from various limitations, including the use of expensive, toxic reagents and sophisticated protocol to synthesise the phenols. Additionally, some of these reported literatures employed endangered metals, in which mankind is facing the risk of limited supply of these elements in 20 years’ time from now. As such, a viable alternative and green method for achieving organic synthesis is highly sought after by the chemists of today. Herein, we report for the first time a facile, efficient and alternative method in the preparation of phenols from phenylboronic acids using non-endangered metal as catalyst. In all cases, all phenols were afforded in satisfactory yields (81–96%) by employing column-free method. In the recyclability study, the Sm2O3 catalyst was found to possess good catalytic performance, even after being reused for five consecutive times (96–91%). In addition, SEM result revealed that the morphology of the recycled Sm2O3 catalyst was well preserved after five successive uses, which indicate no observable changes occurred in the recovered catalysts. As a final note, the current method is anticipated to be useful for industries manufacturing chemical intermediates as it provides an alternative method of catalysis by using a non-endangered metal in organic transformations.
- Yusoff, Hanis Mohd,Bala Chandran, Prasana Devi,Sayuti, Fatin Amira Binti,Kan, Su-Yin,Mohd Radzi, Siti Aisha,Yong, Fu-Siong Julius,Lee, Oon Jew,Chia, Poh Wai
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- Cu2O/TiO2 as a sustainable and recyclable photocatalyst for gram-scale synthesis of phenols in water
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A green and straightforward protocol was developed for the synthesis of phenols from aryl boronic acid using an inexpensive and available Cu2O/TiO2 photocatalyst under visible light and sunlight. This approach proceeded in mild reaction conditions in water and the presence of air as a green oxidant, resulting in the corresponding phenols in good to excellent yields. Sunlight was also a sustainable source for this photochemical reaction. Heterogeneous nano photocatalyst was successfully recovered in 8 consecutive runs. It is noteworthy that, the photocatalyst exhibited high activity for the large-scale synthesis of phenols.
- Hosseini-Sarvari, Mona,Keshavarz, Kimia,Tavakolian, Mina
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- Highly efficient heterogeneous V2O5@TiO2 catalyzed the rapid transformation of boronic acids to phenols
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A V2O5@TiO2 catalyzed green and efficient protocol for the hydroxylation of boronic acid into phenol has been developed utilizing environmentally benign oxidant hydrogen peroxide. A wide range of electron-donating and the electron-withdrawing group-containing (hetero)aryl boronic acids were transformed into their corresponding phenol. The methodology was also applied successfully to transform various natural and bioactive molecules like tocopherol, amino acids, cinchonidine, vasicinone, menthol, and pharmaceuticals such as ciprofloxacin, ibuprofen, and paracetamol. The other feature of the methodology includes gram-scale synthetic applicability, recyclability, and short reaction time.
- Upadhyay, Rahul,Singh, Deepak,Maurya, Sushil K.
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supporting information
p. 3925 - 3931
(2021/08/24)
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- Blacklight-Induced Hydroxylation of Arylboronic Acids Leading to Hydroxyarenes Using Molecular Oxygen and Tetrabutylammonium Borohydride
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A new simple protocol for the conversion of arylboronic acids to hydroxyarenes was achieved using molecular oxygen in the presence of tetrabutylammonium borohydride under blacklight irradiation (360 nm). A radical chain mechanism in which a superoxide ion (O2?.) plays a key role is proposed.
- Kawamoto, Takuji,Ryu, Ilhyong
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- Double Insurance of Continuous Band Structure and N-C Layer Induced Prolonging of Carrier Lifetime to Enhance the Long-Wavelength Visible-Light Catalytic Activity of N-Doped In2O3
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Nonmetallic doped metal oxides can be broad in their visible-light-response range. However, the half-filled or isolated impurity state can also be the new recombination center for photogenerated electrons/holes, which seriously influence the photocatalytic activity of the catalyst in the visible-light region. Therefore, how to prolong the photogenerated carrier life of nonmetallic doping metal oxides is the difficult and challenging topic in the field of photocatalysis. In this work, the hexagonal nanosheets assembled by N-doped C (N-C)-coated N-doped In2O3 (N-In2O3) nanoparticles (N-C/N-In2O3 HS) was obtained by simply pyrolyzing the In(2,5-PDC) hexagonal sheets. The N-C/N-In2O3 HS catalyst exhibit good photocatalytic activity and cycle stability in the long-wavelength region of visible light (λ = 520 and 595 nm). The effective utilization of long-wavelength visible light for N-C/N-In2O3 HS was mainly attributed to the acceptor-donor-acceptor compensation mechanism between the oxygen vacancy (VO) and substitutional N-doping (Ns) sites, which made the N-C/N-In2O3 HS possess a continuous band structure, without the half-filled or isolated impurity state in the band gap, and extended its light absorption edge to 733 nm. The compensation mechanism of nitrogen doping on In2O3 can promote the photocatalytic activity under longer-wavelength yellow light (595 nm) irradiation. The N-C layer coated on the N-In2O3 nanoparticles acted as a good acceptor of photogenerated electrons, facilitating the effective spatial separation of photogenerated carriers and extend photogenerated carrier lifetimes. The comparative photocatalytic experiments (N-In2O3 HS and N-C/N-In2O3 HS) show that the presence of N-doped C layer can enhance the photocatalytic efficiency by nearly 10-fold. This double-doping and carbon-coating strategy provided a novel research idea to solve the problem that nonmetal atoms doped metal oxides led to the secondary combination of photogenerated electrons/holes.
- Sun, Liming,He, Xiaoxiao,Zeng, Suyuan,Yuan, Yusheng,Li, Rong,Zhan, Wenwen,Chen, Jinquan,Wang, Xiaojun,Han, Xiguang
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supporting information
p. 1160 - 1171
(2021/01/18)
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- Evaluation of 2-(piperidine-1-yl)-ethyl (PIP) as a protecting group for phenols: Stability to ortho-lithiation conditions and boiling concentrated hydrobromic acid, orthogonality with most common protecting group classes, and deprotection via Cope elimination or by mild Lewis acids
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A new protecting group, 2-(piperidine-1-yl)-ethyl (PIP), was evaluated as a protecting group for phenols. The PIP group was stable to ortho-lithiation conditions and refluxing with concentrated hydrobromic acid. Deprotection was accomplished by two routes, oxidation to N-oxides followed by Cope elimination (CE) and subsequent hydrolysis or ozonolysis of the vinyl ether or one-step deprotection by BBr3?Me2S. The PIP group is orthogonal to the O-benzyl, O-acetyl, O-t-butyldiphenylsilyl, O-methyl, O-p-methoxybenzyl, O-allyl, O-tetrahydropyranyl and N-t-butoxy carbonyl groups. The CE step was systematically studied and was found to give higher yields when the reaction was performed in the presence of silylating agents.
- Norén, Rolf
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- Homogeneous Palladium-Catalyzed Selective Reduction of 2,2′-Biphenols Using HCO 2H as Hydrogen Source
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An efficient homogeneous palladium-catalyzed selective deoxygenation of 2,2′-biphenols by reduction of aryl triflates with HCO 2H as the hydrogen source is reported. This protocol complements the current method based on heterogeneous Pd/C-catalyzed hydrogenation with hydrogen gas. This process provided the reduction products in good to excellent yields, which could be readily converted to various synthetically useful molecules, especially ligands for catalytic synthesis.
- Li, Ruoling,Li, Chenchen,Yang, Wen,Zhao, Wanxiang
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p. 1605 - 1618
(2021/02/01)
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- Synthesis of Trinuclear Benzimidazole-Fused Hybrid Scaffolds by Transition Metal-Free Tandem C(sp2)?N Bond Formation under Microwave Irradiation
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2-(2-Bromoaryl)- and 2-(2-bromovinyl)benzimidazoles have been coupled and cyclized with 2-methoxy- and 2-aryloxybenzimidazoles as building blocks in the presence of a base under microwave irradiation to give a class of trinuclear N-fused hybrid scaffolds, benzo[4,5]imidazo[1,2-a]benzo[4,5]imidazo[1,2-c]quinazolines and -pyrimidines, respectively, in good yields. 2-(2-Bromoaryl)- and 2-(2-bromovinyl)imidazoles also reacted with 2-methoxybenzimidazoles in the presence of base under microwave irradiation to give a class of trinuclear N-fused hybrid scaffolds, benzo[4,5]imidazo[1,2-a]imidazo[1,2-c]quinazolines and -pyrimidines, respectively, in similar yields. This process seems to proceed via an initial C(sp2)-N coupling by an addition-elimination nucleophilic aromatic substitution (SNAr) and subsequent cyclization accompanied by extrusion of alcohols.
- Dao, Pham Duy Quang,Cho, Chan Sik
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p. 4088 - 4098
(2021/06/16)
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- Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
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The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
- Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
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supporting information
p. 16470 - 16485
(2021/10/20)
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- Photocatalytic synthesis of phenols mediated by visible light using KI as catalyst
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A transition-metal-free hydroxylation of iodoarenes to afford substituted phenols is described. The reaction is promoted by KI under white LED light irradiation and uses atmospheric oxygen as oxidant. By the use of triethylamine as base and solvent, the corresponding phenols are obtained in moderate to good yields. Mechanistic studies suggest that KI and catalysis synergistically promote the cleavage of C-I bond to form free aryl radicals.
- Huiqin, Wei,Wu, Mei
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supporting information
(2021/11/30)
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- Palladium-Catalyzed Hydroxylation of Aryl Halides with Boric Acid
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Boric acid, B(OH)3, is proved to be an efficient hydroxide reagent in converting (hetero)aryl halides to the corresponding phenols with a Pd catalyst under mild conditions. Various phenol products were obtained in good to excellent yields. This transformation tolerates a broad range of functional groups and molecules, including base-sensitive substituents and complicated pharmaceutical (hetero)aryl halide molecules.
- Song, Zhi-Qiang,Wang, Dong-Hui
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supporting information
p. 8470 - 8474
(2020/11/18)
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- Visible-light-mediated borylation of aryl and alkyl halides with a palladium complex
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Palladium catalyzed visible-light-mediated borylation of inactivated aryl and alkyl halides is reported; the method provided high yields and excellent functional group compatibility. Furthermore, arylsilicates were synthesized selectively using dimethylphenylsilyl boronic ester via changing the reaction conditions. Finally, the possible reaction mechanism is determined through fluorescence quenching and turn on/off experiments.
- Zhao, Jia-Hui,Zhou, Zhao-Zhao,Zhang, Yue,Su, Xuan,Chen, Xi-Meng,Liang, Yong-Min
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p. 4390 - 4394
(2020/10/20)
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- KMnO4-catalyzed chemoselective deprotection of acetate and controllable deacetylation-oxidation in one pot
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A novel and efficient protocol for chemoselective deacetylation under ambient conditions was developed using catalytic KMnO4. The stoichiometric use of KMnO4 highlighted the dual role of a heterogeneous oxidant enabling direct access to aromatic aldehydes in one-pot sequential deacetylation-oxidation. The reaction employed an alternative solvent system and allowed the clean transformation of benzyl acetate to sensitive aldehyde in a single step while preventing over-oxidation to acids. Use of inexpensive and readily accessible KMnO4 as an environmentally benign reagent and the ease of the reaction operation were particularly attractive, and enabled the controlled oxidation and facile cleavage of acetate in a preceding step. This journal is
- Gurawa, Aakanksha,Kumar, Manoj,Rao, Dodla S.,Kashyap, Sudhir
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supporting information
p. 16702 - 16707
(2020/10/27)
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- Covalent Catalysis by Cross β Amyloid Nanotubes
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The binding pockets of extant enzymes feature precise positioning of amino acid residues that facilitate multiple complex transformations exploiting covalent and non-covalent interactions. Reversible covalent anchoring is extensively used as an efficient tool by Nature for activating modern enzymes such as esterases and dehydratases and also for proteins like opsins for the complex process of visual phototransduction. Here we construct paracrystalline amyloid surfaces through the self-propagation of short peptides which offer binding pockets exposed with arrays of imidazoles and lysines. As covalent catalysis is utilized by modern-day enzymes, these homogeneous amyloid nanotubes exploit Schiff imine formation via the exposed lysines to efficiently hydrolyze both activated and inactivated esters. Controls where lysines were mutated with charged residues accessed similar morphologies but did not augment the rate. The designed amyloid microphases thus foreshadow the generation of binding pockets of advanced proteins and have the potential to contribute to the development of functional materials.
- Chatterjee, Ayan,Das, Dibyendu,Sarkhel, Baishakhi
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supporting information
p. 4098 - 4103
(2020/08/19)
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- Chemoselective Cross-Coupling between Two Different and Unactivated C(aryl)-O Bonds Enabled by Chromium Catalysis
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We report here the first example of cross-coupling between two different and unactivated C(aryl)-O bonds with chromium catalysis. The combination of a low-cost Cr(II) salt, 4,4′-di-tert-butyl-2,2′-dipyridyl (dtbpy) as the ligand, and magnesium as the reductant shows high reactivity in promoting the reductive cross-coupling of aryl methyl ether derivatives with aryl esters by cleavage and coupling of two different C(aryl)-O bonds under mild conditions. The formation of active low-valent Cr species by reduction of CrCl2 with Mg can be considered, which prefers to initially activate the C(aryl)-O bond of phenyl methyl ether with the chelation help of dtbpy and an o-imine auxiliary. The subsequent consecutive reduction, second C(aryl)-O activation, and reductive elimination allow for the achievement of selective cross-coupling of C(aryl)-O/C(aryl)-O bonds.
- Tang, Jinghua,Liu, Liu Leo,Yang, Shangru,Cong, Xuefeng,Luo, Meiming,Zeng, Xiaoming
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supporting information
p. 7715 - 7720
(2020/05/20)
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- Vinylene-Bridged Two-Dimensional Covalent Organic Frameworks via Knoevenagel Condensation of Tricyanomesitylene
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Vinylene-bridged covalent organic frameworks (COFs) have shown great potential for advanced applications because of their high chemical stability and intriguing semiconducting properties. Exploring new functional monomers available for the reticulation of vinylene-bridged COFs and establishing effective reaction conditions are extremely desired for enlarging the realm of this kind of material. In this work, a series of vinylene-bridged two-dimensional (2D) COFs are synthesized by Knoevenagel condensation of tricyanomesitylene with ditopic or tritopic aromatic aldehydes. With use of appropriate secondary amines as catalysts, high-crystalline vinylene-bridged COFs were achieved, exhibiting long-range ordered structures, well-defined nanochannels, high surface areas (up to 1231 m2 g-1), and excellent photophysical properties. Under a low loading amount and short reaction time, they enable aerobic photocatalytic transformation of arylboronic acids to phenols with high efficiency and excellent recyclability. This work demonstrates a new functional monomer, tricyanomesitylene, feasible for the general synthesis of vinylene-bridged COFs with potential application in photocatalytic organic transformation, which instigates further research on such kind of material.
- Bi, Shuai,Thiruvengadam, Palani,Wei, Shice,Zhang, Wenbei,Zhang, Fan,Gao, Lusha,Xu, Junsong,Wu, Dongqing,Chen, Jie-Sheng,Zhang, Fan
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supporting information
p. 11893 - 11900
(2020/08/06)
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- Aerobic photooxidative hydroxylation of boronic acids catalyzed by anthraquinone-containing polymeric photosensitizer
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We report herein the synthesis of a polymeric photosensitizer and its application in aerobic photooxidative hydroxylation of boronic acids. The polymeric photosensitizer was synthesized by the condensation of anthraquinone-2-carbonyl chloride (AQ-2-COCl) with poly (2-hydroxyethyl methacrylate) (PHEMA). The photo-oxidative hydroxylation of boronic acids using anthraquinone-containing-poly (2-hydroxyethyl methacrylate) (AQ-PHEMA) was then explored and shown to exhibit high efficiency and broad scope. Moreover, AQ-PHEMA could be easily recovered and reused for more than 20 times without significant loss of the catalytic activity.
- Chen, Yang,Ding, Aishun,Hu, Jianhua
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p. 7927 - 7932
(2020/03/11)
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- Rongalite-promoted metal-free aerobic ipso-hydroxylation of arylboronic acids under sunlight: DFT mechanistic studies
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A novel rongalite-promoted metal-free aerobic ipso-hydroxylation of arylboronic acids has been developed. This method employs low-cost rongalite as a radical initiator and O2 as a green oxidizing agent for ipso-hydroxylation. This protocol is compatible with a wide variety of functional groups with good to excellent yields at room temperature. Furthermore, mechanistic insight into the role of superoxide radical anions in C-B cleavage has also been provided based on DFT studies.
- Golla, Sivaparwathi,Poshala, Soumya,Pawar, Ravinder,Kokatla, Hari Prasad
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supporting information
(2019/12/27)
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- Nickel-catalyzed oxidative hydroxylation of arylboronic acid: Ni(HBTC)BPY MOF as an efficient and ligand-free catalyst to access phenolic motifs
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A straightforward and mild oxidative ipso-hydroxylation of arylboronic acids has been achieved using a simple and non-noble metal, nickel-based reusable heterogeneous catalyst Ni(HBTC)BPY MOF (HBTC = benzene-1,3,5-tricarboxylate, BPY = 4,4′-bipyridine) in the presence of benign hydrogen peroxide as an oxidant under ambient reaction condition. The Ni(HBTC)BPY MOF exhibits excellent catalytic activity towards the formation of phenols from diverse arylboronic acids within short time and can be reused up to five times without any notable loss in its activity as well as shown high functional group tolerance even in the presence of sensitive functionalities and useful to achieve hydroxyl group in heterocycles.
- Latha, Ganesapandian,Devarajan, Nainamalai,Karthik, Murugan,Suresh, Palaniswamy
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- Bimetallic photoredox catalysis: Visible light-promoted aerobic hydroxylation of arylboronic acids with a dirhodium(ii) catalyst
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We report the use of a rhodium(II) dimer in visible light photoredox catalysis for the aerobic oxidation of arylboronic acids to phenols under mild conditions. Spectroscopic and computational studies indicate that the catalyst Rh2(bpy)2(OAc)4 (1) undergoes metal-metal to ligand charge transfer upon visible light irradiation, which is responsible for catalytic activity. Further reactivity studies demonstrate that 1 is a general photoredox catalyst for diverse oxidation reactions.
- Campbell, Michael G.,Chuang, Gary Jing,Liu, Ming-Lun,Miura-Stempel, Emily,Tu, Jing-Wen,Yang, Hsiang-Ming
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p. 2040 - 2047
(2020/03/13)
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- Quaternary ammonium hydroxide-functionalized g-C3N4 catalyst for aerobic hydroxylation of arylboronic acids to phenols
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A new and efficient metal-free approach toward the synthesis of phenols via an aerobic hydroxylation of arylboronic acids by using a novel quaternary ammonium hydroxide g-C3N4 catalyst has been described. The functionalized quaternary ammonium hydroxide (g-C3N4-OH) has been prepared from graphitic carbon nitride (g-C3N4) scaffold by converting the residual –NH2 and –NH groups to quaternary methyl ammonium iodide by performing a methylation reaction with methyl iodide followed by ion-exchange with 0.1 N KOH or anion exchange resin Amberlyst A26 (OH- form) by post-synthetic modification. The resultant g-C3N4-OH was characterized by XRD, FTIR, field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), N2 adsorption/desorption isotherms, and acid–base titration. Tested as solid-base catalysts, the g-C3N4-OH showed excellent catalytic activity in the aerobic hydroxylation reaction by converting a variety of arylboronic acids to the corresponding phenols in high yields. More importantly, the g-C3N4-OH solid-base has been successfully reused four times with the minor loss of initial catalytic activity (10.5percent).
- Muhammad, Ibrahim,Mannathan, Subramaniyan,Sasidharan, Manickam
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p. 1470 - 1476
(2020/07/13)
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- Synthesis of Phenols via Metal-Free Hydroxylation of Aryl Boronic Acids with Aqueous TBHP
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An alternate procedure for oxidative hydroxylation of aryl boronic acids with aqueous TBHP to access phenols is described. The protocol tolerated various functional groups substituted with aromatic rings. The reaction was performed in water and free from transition metal oxidants.
- Shaikh, Tanveer MahmadAlli
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- Method for preparing alcohol and phenol through aerobic hydroxylation reaction of boric acid derivative in absence of photocatalyst
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The invention discloses a method for preparing alcohol and phenol through aerobic hydroxylation reaction of a boric acid derivative in the absence of a photocatalyst, wherein the boric acid derivativeis aryl boronic acid or alkyl boronic acid, and the corresponding target compounds are respectively a phenol-based compound and an alcohol-based compound. According to the method, by using a boric acid derivative as a reaction substrate, an additive is added under a solvent condition, and a hydroxylation reaction is performed under aerobic and illumination conditions to obtain a corresponding target compound. According to the invention, the new strategy is provided for the synthesis of phenols through aerobic hydroxylation of aryl boronic acid without a photocatalyst; the catalyst-free aerobic hydroxylation method for photocatalysis of aryl boronic acid or alkyl boronic acid by using triethylamine as an additive is firstly disclosed; and the new method has advantages of photocatalyst-freecondition, wide substrate range and good functional group compatibility.
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Paragraph 0025-0028; 0030-0032
(2020/01/25)
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- Donor-acceptor type [4+3] covalent organic frameworks: sub-stoichiometric synthesis and photocatalytic application
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Three unprecedented 2D [4+3] covalent organic frameworks (TTCOF-1, TTCOF-2, and TTCOF-3) have been prepared by substoichiometric condensation of tetratopic and tritopic monomers, overcoming the limitations of the design rules of conventional topologies. By reticulating the tetraphenylethylene (TPE)-based and triazine-based moieties into COF frameworks, novel electron donor-acceptor (D-A) type structures were obtained. These TTCOFs have good photocatalytic activity in aerobic C(sp3)-H bond functionalization and arylboronic acid oxidation driven by visible light, with yields up to 94%. This can expedite possibilities of COFs with new structural and topological complexities and can also expand the application of COF-based photocatalysis in synthetic chemistry.
- Liao, Qiaobo,Xu, Wentao,Huang, Xin,Ke, Can,Zhang, Qi,Xi, Kai,Xie, Jin
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p. 707 - 714
(2020/04/15)
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- Helical Carbenium Ion: A Versatile Organic Photoredox Catalyst for Red-Light-Mediated Reactions
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Red light has the advantages of low energy, less health risks, and high penetration depth through various media. Herein, a helical carbenium ion (N,N′-di-n-propyl-1,13-dimethoxyquinacridinium (nPr-DMQA+) tetrafluoroborate) has been used as an organic photoredox catalyst for photoreductions and photooxidations in the presence of red light (λmax = 640 nm). It has catalyzed red-light-mediated dual transition-metal/photo-redox-catalyzed C-H arylation and intermolecular atom-transfer radical addition through oxidative quenching. Moreover, its potential in photooxidation catalysis has also been demonstrated by successful applications in red-light-induced aerobic oxidative hydroxylation of arylboronic acids and benzylic C(sp3)-H oxygenation through reductive quenching. Thus, a versatile organic photoredox catalyst (helical carbenium ion) for red-light-mediated photoredox reactions has been developed.
- Mei, Liangyong,Veleta, José M.,Gianetti, Thomas L.
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supporting information
p. 12056 - 12061
(2020/08/07)
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- Iridium complex-linked porous organic polymers for recyclable, broad-scope photocatalysis of organic transformations
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Two rigid porous organic polymers (Ir-POP-1 and Ir-POP-2) were prepared from the coupling reactions of tetraphenylmethane tetraborate and two [Ir(ppy)2(dtbbpy)]+-based bitopic linkers and applied as heterogeneous visible-light photocatalysts for organic transformations. Ir-POP-2 was found to exhibit high catalytic activity for a wide range of organic reactions, which include Smiles-Truce rearrangement of alkyliodides, desulfurative conjugate addition to Michael acceptors, and aerobic oxidations of sulfides and arylboronic acids. For all the transformations, Ir-POP-2 could achieve heterogeneous photocatalytic efficiency that rivals that of the homogeneous prototype iridium complexes. This remarkably high photocatalytic performance has been attributed to the large pore size of the conjugated backbone. The new heterogeneous photocatalyst was also highly stable to achieve good recyclability for all the studied reactions and could be reused eight to nineteen times.
- Xu, Zi-Yue,Luo, Yi,Zhang, Dan-Wei,Wang, Hui,Sun, Xing-Wen,Li, Zhan-Ting
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supporting information
p. 136 - 143
(2020/01/21)
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- Nickel-catalyzed removal of alkene protecting group of phenols, alcohols via chain walking process
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An efficient nickel-catalyzed removal of alkene protection group under mild condition with high functional group tolerance through chain walking process has been established. Not only phenolic ethers, but also alcoholic ethers can be tolerated with the retention of stereocenter adjacent to hydroxyl group. The new reaction brings the homoallyl group into a start of new type of protecting group.
- Meng, Chenkai,Niu, Haolin,Ning, Juehan,Wu, Wengang,Yi, Jun
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- Identification of an Oxalamide Ligand for Copper-Catalyzed C?O Couplings from a Pharmaceutical Compound Library
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A typical pharmaceutical compound library is stocked with molecular diversity and could provide a platform for the discovery of new ligand structures. Herein, we describe the use of this approach in combination with high throughput screening to identify N,N’-bis(thiophene-2-ylmethyl)oxalamide as a ligand that is generally effective for copper-catalyzed C?O cross-couplings to prepare both biarylethers as well as phenols under mild conditions.
- Chan, Vincent S.,Krabbe, Scott W.,Li, Changfeng,Sun, Lijie,Liu, Yue,Nett, Alex J.
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- Reductive C-O, C-N, and C-S Cleavage by a Zirconium Catalyzed Hydrometalation/β-Elimination Approach
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A zirconium catalyzed reductive cleavage of Csp3 and Csp2 carbon-heteroatom bonds is reported that makes use of a tethered alkene functionality as a traceless directing group. The reaction is successfully demonstrated on C-O, C-N, and C-S bonds and proposed to proceed via a hydrozirconation/β-heteroatom elimination sequence of an in situ formed zirconium hydride catalyst. The positional isomerization of the catalyst further enables the cleavage of homoallylic ethers and the removal of terminal allyl and propargyl groups.
- Matt, Christof,K?lblin, Frederic,Streuff, Jan
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supporting information
p. 6983 - 6988
(2019/09/09)
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- Radical Truce-Smiles reactions on an isoxazole template: Scope and limitations
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The use of TiCl3-HCl as promotor in the radical Truce-Smiles reactions of 2-(((3,5-dimethylisoxazol-4-yl)sulfonyl)oxy)benzenediazonium salts has been investigated in detail. During these reactions the desired Truce-Smiles rearrangement (via an ipso-substitution reaction) is accompanied by the formation of a number of by-products including dihydrobenzo[5,6][1,2]oxathiino[3,4-d]isoxazole 4,4-dioxides, dioxidobenzo[e][1,2]oxathiin-3-yl)ethan-1-ones, anilines and chloroaromatics. Replacing TiCl3-HCl by Cu(NO3)2-Cu2O as reductant in these reactions was found to afford broadly comparable product distributions. Competition and radical clock experiments also provide an indication of the relative susceptibility of the isoxazole nucleus towards attack by aryl radicals.
- Rashid, Srood O.,Almadhhi, Sultan S.,Berrisford, David J.,Raftery, James,Vitorica-Yrezabal, Inigo,Whitehead, George,Quayle, Peter
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p. 2413 - 2430
(2019/03/23)
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- Phthalocyanine Zinc-catalyzed Hydroxylation of Aryl Boronic Acids under Visible Light
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A visible-light-promoted aerobic oxidative hydroxylation of boronic acids using phthalocyanine zinc as an easily available photosensitizer has been developed. It provided a direct access to synthesize aliphatic alcohols and phenols from boronic acids. The advantages of this approach included the low catalyst loading (0.5 mol%), high efficient, the use of O2 as an oxygen source, wide substrate range, the simple operational process, and mild conditions. (Figure presented.).
- Luo, Dong-Ping,Huang, Yang-Feng,Hong, Xiao-Yi,Chen, Dingben,Li, Guo-Xing,Huang, Xiao-Bo,Gao, Wen-Xia,Liu, Miao-Chang,Zhou, Yun-Bing,Wu, Hua-Yue
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supporting information
p. 961 - 964
(2019/01/25)
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