Subsequent Acid Treatment Research Articles

ChemInform Abstract: Novel Succinct Routes to Quinoxalines and 2‐Benzimidazolylquinoxalines via the Ugi Reaction.

Abstract This Letter reveals a unique, user-friendly, concise two-step, one-pot protocol for the synthesis of highly substituted quinoxalines. Conducting the Ugi reaction with appropriately functionalized classical Ugi reagents with subsequent acid treatment of the Ugi adduct affords collections of diversified quinoxalines in good to excellent yields. The methodology exploits what may be viewed as a ‘convertible carboxylic acid’, which in addition may be captured in an intramolecular sense to generate structurally complex 2-benzimidazolylquinoxalines in a mere two steps.

A medium-term gpt delta rat model as an in vivo system for analysis of renal carcinogenesis and the underlying mode of action

The kidney is a major target site of chemical carcinogenesis. However, a reliable in vivo assay for rapid identification of renal carcinogens has not been established. The purpose of this study was to develop a new medium-term gpt delta rat model (the GNP model) to facilitate identification of renal carcinogens. In this model, we carried out an in vivo mutation assay using unilaterally nephrectomized kidney tissue and a tumor-promoting assay using residual kidney tissue, with diethylnitrosamine (DEN) as the renal tumor initiator. To clarify the optimal time of DEN injection after nephrectomy, time-dependent changes in bromodeoxyuridine-labeling indices in the tubular epithelium of nephrectomized rats were examined. The optimal dose of DEN injection and sufficient duration of subsequent nitrilotriacetic acid treatment were determined for detection of renal preneoplastic lesions. The standard protocol for the GNP model was determined as follows. Six-week-old female gpt delta rats were treated with test chemicals for 4 weeks, followed by a 2-week washout period, and 40mg/kg DEN was administered intraperitoneally to initiate renal carcinogenesis. Unilateral nephrectomy was performed 48h before DEN injection, followed by gpt assays using excised kidney tissues. One week after DEN injection, rats were further exposed to test chemicals for 12 weeks, and histopathological analysis of renal preneoplastic lesions was performed as an indicator of tumor-promoting activity in residual kidney tissue. Validation studies using aristolochic acid, potassium dibasic phosphate, phenylbutazone, and d-limonene indicated the reliability of the GNP model for predicting renal carcinogens and the underlying mode of action.

ChemInform Abstract: Isolation and Complete Structural Assignment of Lycopodium Alkaloid Cernupalhine A: Theoretical Prediction and Total Synthesis Validation.

Cernupalhine A (1) is a trace Lycopodium alkaloid (0.7 mg) possessing a new C17N skeleton with an unusual hydroxydihydrofuranone motif newly isolated from Palhinhaea cernua L. Its complete structural assignment, including absolute stereochemistry, was established through a combination of high-field NMR techniques and computational methods and further unequivocal confirmation by the first asymmetric total synthesis. Following the first total synthesis of lobscurinine (3), 1 was achieved via regio- and stereoselective cyanide ion addition and subsequent acid treatment.

Phosphorus reclamation through hydrothermal carbonization of animal manures.

Projected shortages of global phosphate have prompted investigation of methods that could be employed to capture and recycle phosphate, rather than continue to allow the resource to be essentially irreversibly lost through dilution in surface waters. Hydrothermal carbonization of animal manures from large farms was investigated as a scenario for the reclamation of phosphate for agricultural use and mitigation of the negative environmental impact of phosphate pollution. Hydrothermal reaction conditions were identified for poultry, swine, and cattle manures that resulted in hydrochar yields of 50-60% for all three manures, and >90% of the total phosphorus present in these systems was contained in the hydrochars as precipitated phosphate salts. Phosphate recovery was achieved in yields of 80-90% by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve a pH of 9, and filtration of principally calcium phosphate. Phosphate recovery was achieved in yields of 81-87% based on starting manures by subsequent acid treatment of the hydrochars, addition of base to acid extracts to achieve a pH of 9, and filtration of principally calcium phosphate. Swine and cattle manures produced hydrochars with combustion energy contents comparable to those of high-end sub-bituminous coals.

Ultrathin Exfoliated TiO2 Nanosheets Modified with ZrO2 for Dye-Sensitized Solar Cells

In the present work, we use chemical exfoliation to fabricate ultrathin two-dimensional anatase TiO2 nanosheets (NSs) for application as photoanode materials in dye-sensitized solar cells. For the first time, colloidal Ti0.91O2 NSs are synthesized via chemical exfoliation of a layered precursor (HxTi2–x/4□x/4O4·H2O; □: vacancy, x = 0.7) through ion exchange with tetrabutylammonium (TBA+) cations. The as-prepared Ti0.91O2 NSs are well-dispersed and ultrathin with a lateral size of up to a few micrometers. Subsequent acid treatment induces colloidal Ti0.91O2 to reassemble and precipitate into a gelation form, followed by thermal annealing to convert the Ti0.91O2 gelation into anatase TiO2 nanosheets for applications as photoanode materials in DSSCs. Because of the enhanced light absorption and dye absorption resulting from the high surface area of ultrathin TiO2 nanosheets, the DSSC consisting of 8.8 μm thick TiO2 nanosheet film delivers the highest energy conversion efficiency of 4.76% and the largest shor...

Ionic liquid extraction method for upgrading eucalyptus kraft pulp to high purity dissolving pulp

High purity cellulose from wood is an important raw material for many applications such as cellulosic fibers, films or the manufacture of various cellulose acetate products. Hitherto, multi-step refining processes are needed for an efficient hemicellulose removal, most of them suffering from severe cellulose losses. Recently, a novel method for producing high purity cellulose from bleached paper grade birch kraft pulp was presented. In this so called IONCELL process, hemicelluloses are extracted by an ionic liquid–water mixture and both fractions can be recovered without yield losses or polymer degradation. Herein, it is demonstrated that bleached Eucalyptus urograndis kraft pulp can be refined to high purity acetate grade pulp via the IONCELL process. The hemicellulose content could be reduced from initial 16.6 to 2.4 wt% while persevering the cellulose I crystal form by using an optimized 1-ethyl-3-methylimidazolium dimethylphosphate-water mixture as the extraction medium. The degree of polymerization was then reduced by a sulfuric acid treatment for subsequent acetylation of the pulp, resulting in a final hemicellulose content of 2.2 wt%. When pre-treating the pulp enzymatically with endoxylanase, the final hemicellulose content could be reduced even to 1.7 wt%. For comparison, the eucalyptus kraft pulp was also subjected to cold caustic extraction and the same subsequent acid treatment which led to 3.9 wt% of residual hemicelluloses. The performance in acetylation of all produced pulps was tested and compared to commercial acetate grade pulp. The endoxylanase-IONCELL-treated pulp showed superior properties. Thus, an ecologically and economically efficient alternative for the production of highest value cellulose pulp is presented.

Isolation and complete structural assignment of Lycopodium alkaloid cernupalhine A: theoretical prediction and total synthesis validation.

Cernupalhine A (1) is a trace Lycopodium alkaloid (0.7 mg) possessing a new C17N skeleton with an unusual hydroxydihydrofuranone motif newly isolated from Palhinhaea cernua L. Its complete structural assignment, including absolute stereochemistry, was established through a combination of high-field NMR techniques and computational methods and further unequivocal confirmation by the first asymmetric total synthesis. Following the first total synthesis of lobscurinine (3), 1 was achieved via regio- and stereoselective cyanide ion addition and subsequent acid treatment.

Novel succinct routes to quinoxalines and 2-benzimidazolylquinoxalines via the Ugi reaction

This Letter reveals a unique, user-friendly, concise two-step, one-pot protocol for the synthesis of highly substituted quinoxalines. Conducting the Ugi reaction with appropriately functionalized classical Ugi reagents with subsequent acid treatment of the Ugi adduct affords collections of diversified quinoxalines in good to excellent yields. The methodology exploits what may be viewed as a ‘convertible carboxylic acid’, which in addition may be captured in an intramolecular sense to generate structurally complex 2-benzimidazolylquinoxalines in a mere two steps.

Carbon Nanotubes: In Situ Monitoring the Role of Working Metal Catalyst Nanoparticles for Ultrahigh Purity Single‐Walled Carbon Nanotubes (Adv. Funct. Mater. 40/2013)

The role of metal catalysts in the creation of ultrapure single-walled carbon nanotubes (SWNCTs) is explored by Q. Zhang, F. Wei, and co-workers on page 5066. They promote efficient growth of SWCNTs via partial oxidation of metal@C nanoparticles by CO2, and subsequent acid treatment. This in situ study of the chemical vapor deposition growth and CO2 oxidation of SWCNTs reveals in real-time that the key lies in the low content of nanocarbon impurities and the catalytic oxidation being performed in the proper operation windows.

Using hydrofluoric acid to reduce the contact resistance of screen-printed silicon solar cells – Its recombination impact and a method to eliminate it

Using hydrofluoric acid (HF) to improve the contact resistance of a screen-printed silicon solar cell with a high sheet resistance emitter was found to concurrently reduce its pseudo-fill factor. By treating the cell in phosphoric acid, this impact was found to be significantly reduced or eliminated. In the solar cell presented in this work, the pseudo-fill factor reduced from 82.1% to 79.9% after treating the cell in HF, but increased to 81.8% after a subsequent phosphoric acid treatment. Similar effects were found in three other screen-printed solar cells that were fired at different peak furnace temperatures and belt speeds. It was also shown that the phosphoric acid treatment alone does not affect the pseudo-fill factor of a cell. HF treatment can now be used to reduce the contact resistance of a screen-printed silicon solar cell with a high sheet resistance emitter without suffering from a lower pseudo-fill factor so that the full benefit of a HF treatment on a screen-printed silicon solar cell can be realized. This combination of HF and phosphoric acid treatments can potentially be a useful failure analysis method for screen-printed silicon solar cells in the production line and the laboratory.

Hierarchical H-ZSM-5-supported cobalt for the direct synthesis of gasoline-range hydrocarbons from syngas: Advantages, limitations, and mechanistic insight

The main advantages and limitations of the use of mesoporous H-ZSM-5 as Co support in Fischer–Tropsch synthesis (FTS) are identified by combining a detailed catalyst performance evaluation with a thorough characterization.Mesostructures were created in H-ZSM-5 crystallites by demetalation via subsequent base and acid treatments. Desilication through base treatment provides H-ZSM-5 with pore sizes and volumes similar to amorphous SiO2 (a conventional carrier), while acid treatment removes the produced extraframework aluminum and boosts the FTS catalyst activity. Model acid-catalyzed reactions and induced deactivation of zeolite acid sites confirm that hydrocracking of primary FTS hydrocarbons at the zeolite strongly increases the selectivity toward C5–C11 (gasoline fraction). On the other hand, the strong Co–zeolite interaction as revealed by TPR(H2) results in the stabilization of lower coordinated Co sites (as revealed by IR-assisted CO adsorption) and in a higher selectivity toward methane. n-Hexane conversion reactions suggest that the latter is due to increased activity for hydrogenation and hydrocarbon hydrogenolysis reactions at such coordinatively unsaturated Co sites.

Low‐Temperature Transformation of Titania Thin Films from Amorphous Nanowires to Crystallized Nanoflowers for Heterogeneous Photocatalysis

Titania thin films with ordered nanostructures are of general interest in fields of photocatalysis, gas sensors, energy storages, energy conversions, etc. In this study, we report a low‐temperature crystallization and the simultaneously occurred morphology change of titania thin films in a dilute H2SO4 solution. Amorphous titania nanowire arrays were fabricated by a Ti–H2O2 interaction, which transformed to crystallized nanoflower arrays through a dissolution–precipitation route during the subsequent acid treatments. The nanoflowers were doped with nitrogen and also incorporated with sulfate ions. An increasing H2SO4 concentration resulted in larger nanoflowers with higher anatase content; but the crystallinity reduced. The low‐temperature‐derived nanoflower arrays possessed high density of surface hydroxyl groups and defect VO‐Ti3+ sites, which contributed to a high absorption and enhanced photodegradation efficiency of rhodamine B in water under the illumination of UV–visible light during the first several runs of photocatalytic evaluations. The beneficial surface defects diminished gradually with increasing runs; however, the average reaction rate constants of the acid treated films are still superior to that of the calcinated one, which can be attributed to several structural parameters such as the nanoflower morphology, incorporation of sulfate ions, and the coexistence of anatase and rutile.

Effect of Mesopore in MgO Templated Mesoporous Carbon Electrode on Capacitor Performance

Mesoporous carbons (MPCs) with high specific surface area were synthesized by the heat-treatment and subsequent acid treatment of magnesium citrate. The MPCs obtained were examined as electrode materials for electric double layer capacitor and showed the huge gravimetric capacitance with superior rate performance in sulphuric acid electrolyte. The MPCs also realize the larger capacitance than conventional activated carbon in organic electrolyte and extraordinary high retention of capacitance at very low temperature, such as 80% of room temperature value at −60°C.

ChemInform Abstract: Synthesis of Tetrazolo‐Fused Benzodiazepines and Benzodiazepinones by a Two‐Step Protocol Using an Ugi‐Azide Reaction for Initial Diversity Generation.

ChemInformVolume 43, Issue 49 Heterocyclic Compounds ChemInform Abstract: Synthesis of Tetrazolo-Fused Benzodiazepines and Benzodiazepinones by a Two-Step Protocol Using an Ugi-Azide Reaction for Initial Diversity Generation. Steven Gunawan, Steven Gunawan Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorMuhammad Ayaz, Muhammad Ayaz Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorFabio De Moliner, Fabio De Moliner Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorBrendan Frett, Brendan Frett Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorChristine Kaiser, Christine Kaiser Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorNina Patrick, Nina Patrick Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorZhigang Xu, Zhigang Xu Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorChristopher Hulme, Christopher Hulme Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this author Steven Gunawan, Steven Gunawan Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorMuhammad Ayaz, Muhammad Ayaz Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorFabio De Moliner, Fabio De Moliner Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorBrendan Frett, Brendan Frett Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorChristine Kaiser, Christine Kaiser Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorNina Patrick, Nina Patrick Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorZhigang Xu, Zhigang Xu Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this authorChristopher Hulme, Christopher Hulme Dep. Pharmacol. Toxicol., Coll. Pharm., Univ. Ariz., Oro Valley, AZ 85737, USASearch for more papers by this author First published: 19 November 2012 https://doi.org/10.1002/chin.201249188Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume43, Issue49December 4, 2012 RelatedInformation

Surface and Pore Structure Assessment of Hierarchical MFI Zeolites by Advanced Water and Argon Sorption Studies

Advanced physicochemical characterization of the pore structure of hierarchical zeolites, including the precise knowledge of pore size, interconnectivity, and surface properties, is crucial in order to interpret their superior performance in catalytic and adsorption applications. Postsynthetic mesopore formation by alkaline treatment of zeolites leads to simultaneous compositional changes due to the selective dissolution of silicon. By careful tuning of these effects through subsequent acid treatment, the Si/Al ratio can be restored to that of the parent zeolite. We evaluate the application of argon (87.3 K) and water (298.5 K) adsorption to assess the porous properties of mesoporous ZSM-5 zeolites with equivalent porosity, but differing composition. An accurate and combined micro/mesopore size analysis is obtained by applying NLDFT (nonlocal density functional theory) analysis on the argon isotherms. The argon adsorption data clearly reveal the two different relative pressure regions of micro- and mesopo...

Stepwise construction of a 4-hydroxyphenyl functionalized O,N,N-tridentate ferrocene-containing enaminone: Spectral, analytical and structural studies

Tetrahydropyranylation of methyl-4-hydroxybenzoate proceeds with formation of its corresponding THP aromatic ether THP–O–p-C6H4CO2CH3 (1; THP=tetrahydropyranyl, C5H9O). Reaction with in situ generated carbanion of acetylferrocene gave the protected organometallic complex Fc–C(O)CHC(OH)(p-C6H4–O–THP) (2, Fc(η5–C5H5)Fe(η5–C5H4)) featuring keto-enol functionality; subsequent acidic treatment of 2 afforded the 4-hydroxyphenyl substituted counterpart Fc–C(O)CHC(OH)(p-C6H4OH) (3) that exists as a 73/27 mixture of keto-enol/β-diketone tautomers in DMSO solution. The functionalized tridentate metalloligand Fc–C(O)CHC(p-C6H4OH)N(H)CH2CH2NH2 (4) incorporating O,N,N-donors is readily obtained upon Schiff base condensation of 3 with 1,2-diaminoethane. Complex 4 exists exclusively as its ferrocenyl-enaminone tautomer in solution and in the solid state. Compounds 1–4 were characterized by NMR (1H, 13C) and IR spectroscopy as well as by elemental analysis and single-crystal X-ray diffraction.

Synthesis of tetrazolo-fused benzodiazepines and benzodiazepinones by a two-step protocol using an Ugi-azide reaction for initial diversity generation

A two-step strategy for the synthesis of arrays of tricyclic tetrazolo-fused benzodiazepines and benzodiazepinones has been investigated. The protocol uses ortho-N-Boc phenylisocyanides and phenylglyoxaldehydes or ethyl glyoxylate in the four-component Ugi-azide reaction to afford MCR (MultiComponent Reactions) derived adducts equipped with the desired diversity inputs. A subsequent acidic treatment (TFA/DCE) allows a simultaneous deprotection–cyclization leading to the final products.

Concise One-Pot Preparation of Unique Bis-Pyrrolidinone Tetrazoles

A one-pot, two-step synthesis of bis-pyrrolidinone tetrazoles has been established via the Ugi-Azide reaction using methyl levulinate, primary amines, isocyanides and azidotrimethylsilane with subsequent acid treatment to catalyze the lactam formation. The efficiency of the protocol was established followed by a successful transition to library production in four 24-well plates.

Synthesis and surface characterization of silica nanoparticles from industrial resin waste controlled by optimal gelation conditions

Electrical and electronic waste is one of the fastest-growing industrial wastes. This paper examined the silicon extracted form electronic packaging resin ash with a subsequent acidic treatment for silica nanoparticle production. The experimental results showed that sample surface characteristics were highly dependent on the sodium silicate concentration, aging temperature, aging time, gelation pH, etc. The surface areas of the silica ranged from 214 to 664m2/g and the particle sizes ranged from 5 to 30nm. The results of this study will provide a sensible solution for the recycling of silicon-containing industrial waste for a new value-added product.

Concise route to a series of novel 3-(tetrazol-5-yl)quinoxalin-2(1H)-ones

This Letter presents a novel three step solution phase protocol to synthesize 3-(tetrazol-5-yl)quinoxalin-2(1H)-ones. The strategy utilizes ethyl glyoxalate and mono-N-Boc-protected-o-phenylenediamine derivatives in the Ugi-Azide multi-component reaction (MCR) to generate a unique 1,5-disubstituted tetrazole. Subsequent acid treatment stimulates a simultaneous Boc deprotection and intramolecular cyclization leading to bis-3,4-dihydroquinoxalinone tetrazoles. Direct oxidation using a stable solid-phase radical catalyst (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) with ceric ammonium nitrate (CAN) in catalytic fashion initiating aerobic oxidation, completes the entire procedure to generate a series of original unique bis-quinoxalinone tetrazoles. The method was also expanded to produce a bis-benzodiazepine tetrazole.