Novel reactions of carbon suboxide. VI. Synthesis of 2-Oxo-1-benzopyran- and 2-oxoquinoline-3-carboxylic acid hydrazides

A simple, one step synthesis of 2-oxo-1-benzopyran- and 2-oxoquinoline-3-carboxylic acid hydrazides from carbon suboxide and hydrazones is described.     

Contact Ion Pairs on a Protonated Azamacrocycle: the Role of the Anion Basicity

A potassium-containing hexaazamacrocyclic dication, [M?H?K]²⁺, is able to add in the gas phase mono- and dicarboxylate anions as well as inorganic anions by forming the corresponding monocharged adducts, the structure of which markedly depends on the basicity of the anion. With anions, such as acetate or fluoride, the neutral hexaazamacrocycle M acts as an acceptor of monosolvated K⁺ ion. With less basic anions, such as trifluoroacetate or chloride, the protonated hexaazamacrocycle [M?H]⁺ performs the unusual functions of an acceptor of contact K⁺/anion pairs.

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Using density functional theory to calculate the anomeric effect in hydroxylamine and hydrazide derivatives of tetrahydropyran

Little is known about the magnitude of the anomeric effect in N-glycosylated oxyamines and hydrazides, limiting efforts toward the design of chemoselective acceptors that impose a stereochemical preference on glycosylation reactions. Thus, density functional theory (DFT) calculations were conducted to estimate the magnitude of the anomeric effect in N,O-dimethyl-N-(tetrahydro-2H-pyran-2-yl)hydroxylamine (1) and N'-(tetrahydro-2H-pyran-2-yl)acetohydrazide (3). The results show that N,O-dimethyl-N-(tetrahydro-2H-pyran-2-yl)hydroxylamine (1) displays a significant anomeric effect (AE_corr = 1.38 kcal/mol) and that N'-(tetrahydro-2H-pyran-2-yl)acetohydrazide (3) displays a modest anomeric effect (AE_corr = 0.54 kcal/mol).     

Elemental Bromine Production by TiO2 Photocatalysis and/or Ozonation

Significant production of elemental bromine (Br₂) was observed for the first time when treating bromide containing solutions at acidic pH, with TiO₂ photocatalyst, ozone, or a combination thereof. Br₂ selectivities up to approximately 85 % were obtained and the corresponding bromine mass balance values satisfied. The process is general and may be applied at a laboratory scale for green bromination reactions, or industrially as a cheap, safe, and environmentally sustainable alternative to the currently applied bromine production methods.     

Mimicking of Chondrocyte Microenvironment Using In Situ Forming Dendritic Polyglycerol Sulfate‐Based Synthetic Polyanionic Hydrogels

A stable polymeric network that mimics the highly polyanionic extracellular cartilage matrix still remains a great challenge. The main aim of this study is to present the synthesis of dendritic polyglycerol sulfate (dPGS)‐based in situ forming hydrogels using strain promoted azide‐alkyne cycloaddition reactions. A real time rheological study has been used to characterize the hydrogel properties. The viability of encapsulated human chondrocytes in the different hydrogels are monitored using live‐dead staining. Furthermore, type I and II collagen gene have been analyzed. Hydrogels with elastic moduli ranging from 1 to 5 kPa have been prepared by varying the dPGS amount. The chondrocyte viability in dPGS hydrogels is found to be higher than in pure PEG and alginate‐based hydrogels after 21 d. The higher cell viability in the dPGS engineered hydrogels can be explained by the fact that dPGS can interact with different proteins responsible for cell growth and proliferation.

     

Rapid synthesis of oligosaccharides using an anomeric fluorous silyl protecting group

A fluorous silyl ether tag as protecting group at the anomeric position of sugar acceptors allows rapid synthesis of oligosaccharides by reducing the purification procedures to a simple and fast fluorous solid-phase extraction.     

Photocatalytic degradation of actual textile industrial wastewater in aqueous suspensions of polycrystalline TiO2

Heterogeneous photocatalytic oxidation of contaminants present in wastewater produced by a textile industry was carried out. The samples were withdrawn from the plant before and after a traditional biological treatment. The effluents were named A and A' (before the biological treatment), B and B' (after the biological treatment). Polycrystalline TiO2 (Degussa P25) was used as the catalyst in a batch photoreactor with immersed lamp. An almost complete decolorization was observed after about 0.5 divided by 1 hours for both kinds of effluents, but the decrease of the total organic carbon (TOC) concentration occurred more slowly. The influence of some chemical oxidants, i.e. ozone, hydrogen peroxide and peroxydisulfate on the photo-oxidation rate was also investigated. After addition of H2O2 or S2O8(2-) TOC decreased more quickly only for B and B'. The runs performed by using O3 as bubbling gas showed a mineralization rate higher than that observed in the presence of O2.     

New reactions of carbon suboxide with alkynes

Synthesis of 3,4,7,8‐tetraalkyl‐2‐oxa‐bicyclo[4.2.0]octa‐1(6),3,7‐trien‐5‐ones( 4a‐d ),4,5,7,8‐tetraalkyl‐2‐oxa‐bicyclo[4.2.0]octa‐1(6),4,7‐trien‐3‐ones ( 6a‐d ) and 3,4,7,8‐tetraalkyl‐2H,5H‐cyclobuta[b]pyrano‐[2,3‐d]pyran‐2,5‐diones ( 7a‐d ) from the reaction of alkynes ( la‐d ) with carbon suboxide ( 2 ) in various molar ratios is described.     

Degenerate two-photon absorption spectra in azoaromatic compounds.

A systematic study of the degenerate two-photon absorption (2PA) spectra of seven azoaromatic compounds in dimethyl sulfoxide solution is reported, which employed the Z-scan technique with femtosecond laser pulses from the bottom of the azo compound absorption bands up to 1100 nm. The 2PA peaks for pseudostilbene-type azo compounds (Disperse Orange (DO) 3, Disperse Red (DR) 13, DR1, DR19, and DR19-Cl) were observed at twice the peak wavelength of the linear absorption. However, such peaks were not observed for other azo compounds (PAMINO and DIAMINO) because of the symmetry of these molecules. A resonance enhancement of the 2PA cross-section was observed for all compounds. The 2PA peak and the nonlinear resonance enhancement behavior could be adjusted with a model based on perturbation theory. Such knowledge can be a guideline to the understanding of the 2PA process in azoaromatic compounds.