Synthesis, spectral luminescent and scintillation properties of organic luminophores based on carbonyl-containing derivatives of 2-(fur-2-yl)-5-phenyloxazole

A series of derivatives of 2-(fur-2-yl)-5-phenyloxazole with various substituents in the 5-position of the furan ring and furan-containing analogs of 1,4-bis(5-phenyloxazol-2-yl)benzene are synthesized. Their spectral-luminescent properties are investigated.Institute of Single Crystals, National Academy of Sciences of Ukraine, Kharkov 310001Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 317–323, March, 1999.     

THE PHOTOTOXICITY OF 2,5-DIPHENYLOXAZOLE (POP) AND 1,4-BIS(5-PHENYLOXAZOL-2-YL)BENZENE (POPOP)

Abstract 2,5-Diphenyloxazole (POP) is widely used for the determination of radioactivity by scintillation counting. It has been found to be phototoxic to the yeasts Saccharomyces cerevisiae and Candida utilis , to the first instar larvae of the mosquito Aedes aegypti , to the crustaceans Daphnia magna and Artemia salida , as well as to the eggs of Drosophila melanogaster . The related molecule 1,4-bis(5-phenyloxazol-2-yl)benzene (POPOP) is also phototoxic, but to a lesser degree. Both POP and POPOP can sensitize the formation of singlet oxygen.     

New and efficient high Stokes shift fluorescent compounds: unsymmetrically substituted 1,2-bis-(5-phenyloxazol-2-yl)benzenes via microwave-assisted nucleophilic substitution of fluorine

Two new unsymmetric derivatives of 1,2-bis-(5-phenyloxazol-2-yl)benzene (ortho-POPOP) were synthesized via microwave-assisted nucleophilic substitution of fluorine which appears to be significantly more efficient compared with conventional thermal activation. The compounds synthesized are characterized by high fluorescence Stokes shifts (6000-11,000 cm⁻¹) in solvents of various polarity, intermediate-to-high fluorescence quantum yields and lifetimes in the range of several nanoseconds.     

Structural characterization of two oxadiazolic systems used as spacers for potential angiotensin II receptor antagonists

The structures of two oxadiazole derivatives, methyl 2-[5-(4-methylphenyl)-1,3,4-oxadiazol-2-yl]benzoate (1) and methyl 2-[3-(4-methylphenyl)-1,2,4-oxadiazol-5-yl]benzoate2, used as spacers in the synthesis of new potential non-peptide angiotensin receptor antagonists have been determined by X-ray crystallography. In both compounds π-π interactions were observed between the oxadiazole rings and the phenyl rings of neighboring molecules. In the crystal packing of the oxadiazole 2 two C-H?O interactions are present.     

Molecular structure and conformations of a sterically hindered aryl derivative of 1,3,4-oxadiazole containing an o,o′-biphenyl ring system

The structure of sterically hindered molecules of 2,2-bis(5-phenyl-1-,3,4-oxadiazol-2-yl)biphenyl has been studied. Crystals that are suitable for x-ray diffraction analysis can be obtained for the different conformers of this compound. It has been found that during synthesis the molecule of this compound is obtained in an energetically less favorable conformation. On the basis of model calculations using the AMI method with geometry optimization it has been proposed that during synthesis there are no changes in conformation of either the intermediates or the final product and the conformation of the resulting oxadiazole system is governed by the conformation of the initial 2,2-diphenic acid dichloride.Khar'kov State University, Khar'kov 310077. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 984–991, July 1996. Original article submitted April 23, 1996.     

Reaction of arylidene derivatives of Meldrum's acid with 3-amino-1,2,4-triazole

The condensation of arylidene derivatives of Meldrum's acid with 3-amino-1,2,4-triazole in nitrobenzene leads to 4,5,6,7-tetrahydro-1,2,4-triazolo [1,5-a]pyrimidin-5-ones. In DMF the reaction proceeds with the formation of arylsubstituted N-(2H-1,2,4-triazol-3-yl)-3-(2H-1,2,4-triazol-3-ylamino)propionamides. Ukrainian Research Institute for the Pharmacotherapy of Endocrine Diseases, Kharkov 310002. Kharkov State University, Kharkov 310077, Ukraine     

A novel acyclic addition of ketenes to oxazoles/oxazolines

The addition of n-butyryl chloride (1) to 5-phenyloxazole (6) or 4,5-dihydro-5-methyl-4-[(4′-methylphenyl)-sulfonyl]oxazole (8) in the presence of triethylamine lead to 1-(5′-phenyloxazol-2′-yl)-1-buten-1-yl butanoate (7) and 1-(5′-methyl-4′-[4″-methylphenylsulfonyl]4′,5′-dihydrooxazol-2′-yl)-1-buten-1-yl butanoate (9) , respectively.     

Imine-enamine tautomerism of dihydroazolopyrimidines. 6. Synthesis and tautomerism of thienyl derivatives of dihydro-1,2,4-triazolo-[1,5-a]pyrimidines

The cyclocondensation of thiophene analogs of chalcone with 3-amino-1,2,4-triazole gives 5- and 7-(α-thienyl)dihydro-1,2,4-triazolo[1,5-a]pyrimidines. The tautomer composition of synthesized compounds was analyzed. For communication 5, see [1]. Kharkov State University, 310077 Kharkov, Ukraine, Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 678–682, May, 1999.     

Theoretical investigation of the reaction of unsymmetrical 3,6-disubstituted <Emphasis Type="Italic">sym</Emphasis>-tetrazines with certain enamines

A theoretical investigation has been carried out of the reaction of 6-(3,5-dimethylpyrazol-1-yl)-sym-tetrazin-3-ylhydrazones of ketones with enamines such as 1-morpholinocyclopentene and 1-piperidino-cyclopentene. A [4+2] cycloaddition mechanism of unsymmetrical 3,6-disubstituted tetrazines with enamines is proposed (the Carboni–Lindsey reaction). As a result only one product is preferentially obtained, having a substituent in the ortho position relative to the dimethylpyrazolyl radical, however in the case of small steric problems under kinetic conditions, control of the process is possible and all possible stereoisomers are obtained.     

Synthesis of novel 5-chloro-2-(thiophen-2-yl)-7,8-dihydroquinoline-6-carboxamides as potent inhibitors of Mycobacterium tuberculosis

A series of novel 5-chloro-2-(thiophen-2-yl)-7,8-dihydroquinoline-6-carboxamides was designed, synthesized, and evaluated for antitubercular activity. The required 5-chloro-2-(thiophen-2-yl)-7,8-dihydroquinoline-6-carboxylic acid intermediate was prepared by oxidizing the respective aldehyde with sodium chlorite and 30% H2O2. Further, the acid was coupled with various aryl, alkyl, and heterocyclic amines using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and hydroxybenzotriazole to give the desired 5-chloro-2-(thiophen-2-yl)-7,8-dihydroquinoline-6-carboxamides in excellent yields. All the new compounds were characterized by their NMR and mass spectral analysis. Screening of all new compounds for in vitro antimycobacterial activity against M. tuberculosis H37Rv (Mtb) resulted in five analogs with MIC 3.12 µg/cm3 as promising antitubercular agents with lower cytotoxicity profiles.     

Improved mesophase stability of benzoxazole derivatives via dipole moment modification

By modifying the molecular dipole moments with lateral monofluorine substituent, improved mesophase stabilities were obtained for novel benzoxazole derivatives, 2-(4?-alkoxy-3-fluorobiphenyl-4-yl)-benzoxazole liquid crystals (coded as nPPF(3)Bx). The series of nPPF(3)Bx with lateral monofluorine substituent ortho to benzoxazole group have larger calculated dipole moments by about 2 D than the corresponding fluorine-substituted analogs (compounds I) with lateral monofluorine ortho to alkoxy group; it is interesting to note that they show lower melting and clearing points but better mesophase stability with wider mesophase ranges for the molecules with both polar (NO₂, Cl) and nonpolar (CH₃, H) terminal groups. Meanwhile, compounds nPPF(3)Bx show greater red-shifted photoluminescence emissions than compounds I, which suggest that π–π interaction between molecules is reinforced by the enhanced dipole–dipole interaction caused by increased dipole moments. These results suggest that modification of the molecular dipole moment is an effective method to improve the mesophase stability of the classical mesogenic compounds.     

Selective Stille coupling reactions of 3-chloro-5-halo(pseudohalo)-4H-1,2,6-thiadiazin-4-ones

A series of 3-chloro-5-halo(pseudohalo)-4H-1,2,6-thiadiazin-4-ones (halo/pseudohalo = Br, I, OTf) are prepared from 3,5-dichloro-4H-1,2,6-thiadiazin-4-one (3) in good yields. Of these the triflate reacts with tributyltin arenes (Stille couplings) chemoselectively to give only the 5-aryl-3-chloro-4H-1,2,6-thiadiazin-4-ones in high yields. This allowed the preparation of a series of unsymmetrical biaryl thiadiazines and ultimately a series of oligomers. Furthermore, treatment of 3-chloro-5-iodo-4H-1,2,6-thiadiazin-4-one (10) with Bu(3)SnH and Pd(OAc)(2) gave the bithiadiazinone which can also be further arylated via the Stille reaction to give bisthien-2-yl and bis(N-methylpyrrol-2-yl) analogs.     

Synthesis and GCP II inhibitory activity of 4[4-(3-bromobenzyl)-5-hydroxyisoxazol-3-yl]benzoic acid heterocyclic analogs

A method for the synthesis of analogs of glutamate carboxypeptidase II inhibitor 4-[4-(3-bromobenzyl)-5-hydroxyisoxazol-3-yl]benzoic acid-4-[4-(3-bromobenzyl-5-hydroxypyrazol-3-yl]-benzoic acid and 4-[4-(3-bromobenzyl)-3-hydroxyisoxazol-5-yl]benzoic acid from 4-(2-ethoxycarbonylacetyl)benzoic acid was developed. The GCP II inhibitory activity of all the compounds synthesized was determined. Substitution of the 5-hydroxyisoxazole group by the 5-hydroxypyrazole group led toa complete loss of activity, while replacement with the 3-hydroxyylisoxazole gave the compound with slightly less inhibitoer activity comparing with the initial compound. __________ Translated from Khimiya Geteritsiklicheskikh Soedinenii, No. 11, 1693–1697, November, 2007.     

Photochromic dihetarylethenes

The structures of two hetarylethene photochromes,viz., 1,2-bis(2-ethyl-5-ethylsulfonylthien-3-yl)perfluorocyclopentene and 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene, were established by X-ray diffraction analysis. The conformational parameters of the title compounds are considered. The cyclopentene ring in the former compound is planar and this ring in the latter compound adopts an envelope conformation. There are no overall conjugated systems in the molecules under study. In both structures, the dihetaryl fragments are rotated with respect to the perfluorocyclopentene fragments by ∼55°. The thiophene and benzoxazole rings in 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene are coplanar. For Part 3, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 74–77, January, 2000.     

Synthesis of （S）-2-（3-Arylacrylamido）-3-{4-[2-（5-methyl-2-phenyloxazol-4-yl）ethoxy]phenyl}propanoic Acids

The synthesis of （S）-2-（3-arylacrylamido）-3-{4-[2-（5-methyl-2-phenyloxazol-4-yl）etho- xy]phenyl}propanoic acids is described. Their structures were confirmed by ^1H-NMR.     

Photochromic dihetarylethenes

The structures of two hetarylethene photochromes,viz., 1,2-bis(2-ethyl-5-ethylsulfonylthien-3-yl)perfluorocyclopentene and 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene, were established by X-ray diffraction analysis. The conformational parameters of the title compounds are considered. The cyclopentene ring in the former compound is planar and this ring in the latter compound adopts an envelope conformation. There are no overall conjugated systems in the molecules under study. In both structures, the dihetaryl fragments are rotated with respect to the perfluorocyclopentene fragments by ∼55°. The thiophene and benzoxazole rings in 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene are coplanar. For Part 3, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 74–77, January, 2000.     

Conformational flexibility of 1,3-cyclohexadiene and its aza analogs

The conformational flexibility of 1,3-cyclohexadiene and its analogs — pyridine and pyrimidine derivatives— was studied by HF/6-31G** ab initio quantum chemical calculations. The potential surface calculations and normal vibration shape analysis show that the molecules exhibit two weakly coupled ring deformation modes. One of the modes may be described as rotation around the C(sp₃)-C(sp₂) bond leading to a transition state of the ring inversion process. The other mode involves flattening of the butadiene fragment and a loss of planarity for endocyclic double bonds without any pronounced changes in the conformation of the saturated part of the molecule. An accurate calculation of the ring inversion barrier demands inclusion of electron correlation effects. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 3, pp. 474-479, May-June, 2000.     

X-ray structures and pharmacological activities of lidocaine derivatives

The molecular and crystal structures of the lidocaine analogs 2-(pyrazol-1-yl)-2′-methylacetanilide (1), 2-(3,5-dimethyl-4-iodo-pyrazol-1-yl)-2′-methylacetanilide (2), 2-(3,5-dimethyl-4-iodo-pyrazol-1-yl)-3′-methylacetanilide (3), and 2-(pyrazol-1-yl)-4′-methylacetanilide (4), are reported, with a summary of their pharmacological activities. In this series, the moiety comprising the heterocyclic ring and the amide alkyl linker displays a common conformation. Molecules of 1–4 form identical hydrogen bonded motifs in their crystals, namely linear chains via intermolecular N–H···O=C hydrogen bonding. Moderate anesthetic and anti-arrhythmic potencies recorded for 1–4 relative to lidocaine are countered by their significantly lower toxicities.     

Synthesis of Nanostructured Organosilicon Luminophores Based on Phenyloxazoles

Russian Journal of Organic Chemistry - A series of nanostructured organosilicon luminophores (NOLs) composed of a central 1,4-bis(5-phenyl-1,3-oxazol-2-yl)benzene (POPOP) acceptor chromophore and...     

Crystal structure of the alcoholates and the ansolvate of PNU-97018, an angiotensin II receptor antagonist

The title compound, PNU-97018 [systemic name: 2-butyl-3,6,7,8,9,11-hexahydro-6,9-dimethyl-3-([2'-(2H-tetrazol-5-yl)[1,1'-biphenyl]-4-yl]methyl)-6,9-ethano-4H-imidazo[4,5-d]-pyridazino[1,2-a]pyridazin-4-one] is a newly developed angiotensin II receptor antagonist. The compound and its methanolate and ethanolate were characterized by X-ray crystallography and thermal analysis. The methanolate and ethanolate crystals have an almost identical molecular conformation and crystal packing. In both alcoholates, each alcohol molecule is fixed to the compound with a molar ratio of 1 : 1 by a hydrogen bond between the hydroxyl group of the alcohol molecule and the tetrazole group of the compound. The hydroxyl group of each alcohol molecule further links with the imidazole ring of the neighboring compound by hydrogen bond to form a hydrogen-bond network in both alcoholates. A tunnel-like structure that includes alcohol molecules is formed in each alcoholate. The ansolvate crystal showed completely different thermal and X-ray crystallographic characteristics from the alcoholates, where the compound molecules were directly linked by hydrogen bonds between the tetrazole group of a molecule and the imidazole ring of the neighboring molecule. The position of the hydrogen atom in the tetrazole ring was different between the ansolvate and alcoholates. Unlike alcoholates, a layer structure stacked on the b-c plane was observed in the ansolvate crystal. It was concluded that the molecular conformation and the arrangement of the compound molecules were largely different between ansolvate and alcoholate crystals.