Fluorinated heterocyclic compounds. A photochemical synthesis of 3-amino-5-perfluoroaryl-1,2,4-oxadiazoles

New Fluorine-Containing Diamine Monomers for Potentially Improved Polyimides

Two new fluorine-containing diamine monomers were designed with the goal of reducing charge transfer complex (CTC) interactions between neighboring chains in polyimides (i.e., high transparency/low color) while hopefully maintaining the well-known thermal stability and flexibility generally associated with polyimides. The proposed diamines have been prepared through (1) the functionalization of 1,3-bis[(pentafluorobenzyl)oxy]benzene with 4-aminophenol and (2) the addition of 2-chloro-5-nitrobenzotrifluoride to 4,4'-bicyclohexanol followed by reduction of the resulting dinitro compound. The new compounds have been characterized by multinuclear NMR and IR spectroscopy and high-resolution liquid chromatography-mass spectrometry as well as single-crystal X-ray diffraction on the new diamine prepared from 4,4'-bicyclohexanol. Not only was the structure of the proposed new diamine confirmed, but another interesting example of hydrogen bonding between an N-H proton and the π-system of an aromatic ring was observed and documented. Initial polymerizations have been carried out via the two-step imidization process.

Fluorescent and Phosphorescent Nitrogen-Containing Heterocycles and Crown Ethers: Biological and Pharmaceutical Applications

Fluorescent molecules absorb photons of specific wavelengths and emit a longer wavelength photon within nanoseconds. Recently, fluorescent materials have been widely used in the life and material sciences. Fluorescently labelled heterocyclic compounds are useful in bioanalytical applications, including in vivo imaging, high throughput screening, diagnostics, and light-emitting diodes. These compounds have various therapeutic properties, including antifungal, antitumor, antimalarial, anti-inflammatory, and analgesic activities. Different neutral fluorescent markers containing nitrogen heterocycles (quinolones, azafluoranthenes, pyrazoloquinolines, etc.) have several electrochemical, biological, and nonlinear optic applications. Photodynamic therapy (PDT), which destroys tumors and keeps normal tissues safe, works in the presence of molecular oxygen with light and a photosensitizing drugs (dye) to obtain a therapeutic effect. These compounds can potentially be effective templates for producing devices used in biological research. Blending crown compounds with fluorescent residues to create sensors has been frequently investigated. Florescent heterocyclic compounds (crown ether) increase metal solubility in non-aqueous fluids, broadening the application window. Fluorescent supramolecular polymers have widespread use in fluorescent materials, fluorescence probing, data storage, bio-imaging, drug administration, reproduction, biocatalysis, and cancer treatment. The employment of fluorophores, including organic chromophores and crown ethers, which have high selectivity, sensitivity, and stability constants, opens up new avenues for research. Fluorescent organic compounds are gaining importance in the biological world daily because of their diverse functionality with remarkable structural features and positive properties in the fields of medicine, photochemistry, and spectroscopy.

Targeting Nonsense: Optimization of 1,2,4-Oxadiazole TRIDs to Rescue CFTR Expression and Functionality in Cystic Fibrosis Cell Model Systems

Cystic fibrosis (CF) patients develop a severe form of the disease when the cystic fibrosis transmembrane conductance regulator (CFTR) gene is affected by nonsense mutations. Nonsense mutations are responsible for the presence of a premature termination codon (PTC) in the mRNA, creating a lack of functional protein. In this context, translational readthrough-inducing drugs (TRIDs) represent a promising approach to correct the basic defect caused by PTCs. By using computational optimization and biological screening, we identified three new small molecules showing high readthrough activity. The activity of these compounds has been verified by evaluating CFTR expression and functionality after treatment with the selected molecules in cells expressing nonsense–CFTR–mRNA. Additionally, the channel functionality was measured by the halide sensitive yellow fluorescent protein (YFP) quenching assay. All three of the new TRIDs displayed high readthrough activity and low toxicity and can be considered for further evaluation as a therapeutic approach toward the second major cause of CF.

Synthesis of fluorinated oxadiazoles with gelation and oxygen storage ability

A new family of fluorinated low molecular weight (LMW) gelators has been synthesized through SNAr substitution of 5-polyfluoroaryl-3-perfluoroheptyl-1,2,4-oxadiazoles with glycine ester. The obtained compounds give thermal and pH-sensitive hydrogels or thermo-reversible organogels in DMSO. Oxygen solubility studies showed the ability to maintain high oxygen levels in solution and in gel blend with plate counter agar (PCA).

Fluoropolymer Based on a Polyaspartamide containing 1,2,4-Oxadiazole Units: A Potential Artificial Oxygen (O2) Carrier

In this preliminary work we have prepared a fluorinated polymer capable of solubilizing an appreciable amount of O(2) and, at the same time, maintaining a higher water solubility than perfluoroalkanes investigated as injectable O(2) carriers. In particular, we describe the synthesis and characterization of a new macromolecular conjugate obtained by derivatization of alpha,beta-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA) with 5-pentafluorophenyl-3-perfluoroheptyl-1,2,4-oxadiazole, called PHEA-F. This new water soluble fluoropolymer was prepared in high yield using a simple procedure. It was characterized by FT-IR and UV-vis spectrophotometry, (19)F-NMR and SEC measurements. O(2) solubility studies on PHEA-F aqueous solutions were carried out at 25 degrees C and 37 degrees C at atmospheric pressure and showed that PHEA-F conjugate, despite its low degree of derivatization in fluorine containing groups (2.60 mol-%), is capable of dissolving 13-15% more O(2) than non-fluorinated PHEA. Moreover, O(2) release in simulated physiological conditions is faster for PHEA-F than for PHEA. The biocompatibility of this conjugate has been evaluated by performing an in vitro viability assay on human chronic myelogenous leukaemia cells (K-562) chosen as a model cell line and in vitro haemolysis experiments on human RBCs. All these properties suggest the potential use of PHEA-F as an artificial O(2) carrier.

Characterization of isomeric 1,2,4-oxadiazolyl-N-methylpyridinium salts by electrospray ionization tandem mass spectrometry

The mass spectrometry behavior of 1,2,4-oxadiazolyl-N-methylpyridinium salts has been investigated. These substances are of current interest as perspective ionic liquids, compounds used as green solvents for synthesis, and for their catalytic properties. The studies have been developed through ESI-MS/MS experiments. The obtained results demonstrate that a readily distinction between the two isomeric classes, 3- N-methylpyridinium- and 5-N-methylpyridinium-1,2,4-oxadiazoles, is possible through ESI-MS/MS experiments. A deeper investigation on the principal fragmentation pathways of characteristic ions has been also developed.

Mass spectrometric analysis of 1,2,4-oxadiazoles and 4,5-dihydro-1,2,4-oxadiazoles

1,2,4-Oxadiazoles and 4,5-dihydro-1,2,4-oxadiazoles are an interesting class of compounds because of their pharmacological and other properties. Although short descriptions of these compounds under mass spectrometric conditions exist, we thought it worthwhile to write a comprehensive review of this class of compounds. Therefore, this revision deals first with 1,2,4-oxadiazoles and then 4,5-dihydro-1,2,4-oxadiazoles from 1964 until the year 2002. Much work on these compounds has been described under electron impact conditions and only a little under chemical ionization (CI).

Photochemistry of fluorinated heterocyclic compounds. An expedient route for the synthesis of fluorinated 1,3,4-oxadiazoles and 1,2,4-triazoles

The photochemistry of some 3-N-alkylamino-5-perfluoroalkyl-1,2,4-oxadiazoles in the presence of nitrogen nucleophiles such as ammonia and primary and secondary aliphatic amines has been investigated. The primary photolytic intermediate from the cleavage of the ring O-N bond follows two distinct and competing pathways leading to (i). 5-perfluoroalkyl-1,3,4-oxadiazoles, through the ring contraction-ring expansion photoisomerization route favored by the presence of the base or (ii). 5-perfluoroalkyl-1,2,4-triazoles, through the intervention, as an internal nucleophile, of the exocyclic N-alkylamino moiety of the oxadiazole followed by the attack of the external nitrogen nucleophile and subsequent heterocyclization. Some comments on the photoreactivity of fluorinated oxadiazoles and on the applications of these photoprocesses in the synthesis of target fluorinated structures are emphasized. In this context, irradiations of 3-perfluoroalkanoylamino-4-phenylfurazan in the presence of primary aliphatic amines are reconsidered as feasible one-pot synthetic methodologies toward fluorinated heterocycles. X-ray analysis of two representative products 1-methyl-3-methylamino-5-perfluoroheptyl-1,2,4-triazole and 2-methylamino-5-trifluoromethyl-1,3,4-oxadiazole confirmed the proposed structures and furnished interesting information on the crystal packing of these fluorinated five-membered heterocycles.

Fluorinated heterocyclic compounds. An expedient route to 5-perfluoroalkyl-1,2,4-triazoles via an unusual hydrazinolysis of 5-perfluoroalkyl-1,2,4-oxadiazoles: first examples of an ANRORC-like reaction in 1,2,4-oxadiazole derivatives

The hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles has been investigated. Nucleophilic addition of the reagent to the C(5)-N(4) double bond of the oxadiazole ring, followed by ring-opening and then ring-closure involving the beta-nitrogen atom of the hydrazino moiety and the C(3) of the oxadiazole ring, explains the formation of 5-perfluoroalkyl-1,2,4-triazoles as final products. Useful applications in synthesis of this uncommon hydrazinolysis can be claimed.