Preparation of dibenzofuran-type amorphous polyetherketone by novel etherification reaction

4-Fluorobenzophenone reacted with potassium carbonate in the presence of silica catalyst in diphenyl sulfone solvent to yield 4,4′-dibenzoyldiphenyl ether. This new etherification reaction was extended to three difluoro aromatic ketones. 4,4′-Bis(4-fluorobenzoyl)diphenyl ether ( I ) reacted with potassium carbonate to yield a crystalline poly(oxy-1,4-phenylene-carbonyl-1,4-phenylene) (PEK) and 4,4′-bis{4-[4-(4-fluorobenzoyl)phenoxy]benzoyl}benzene ( II ) gave a crystalline poly(oxy-1,4-phenylene-carbonyl-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene-carbonyl-1,4-phenylene)(PEKEKEKK). 2,8-Bis(4-fluorobenzoyl)dibenzofuran ( III ) or 2,8-bis(4-chlorobenzoyl)dibenzofuran ( IV ) reacted with potassium carbonate to yield a poly(oxy-1,4-phenylene-carbonyl-2,8-dibenzofuran-carbonyl-1,4-phenylene) (PEKBK). The PEKBK was a noval amorphous polymer with the glass transition temperature of 222°C and it showed excellent thermal stability [T. Tanabe and I. Fukawa, Jpn. Pat., Kokai 64–74223 (1989)]. Several amorphous dibenzofuran type polyetherketone copolymers were prepared by coplycondensation of III with 4,4′-difluorobenzophenone ( V ) or 1,4-bis(4-fluorobenzoyl)benzene ( VI ) [T. Tanabe and I. Fukawa, Jpn. Pat., Kokai 1153722 (1989)]. © 1992 John Wiley & Sons, Inc.     

Bromination of 4-aryl-3,5-dialkoxycarbonyl-2,6-dimethyl-1,4-dihydropyridines

4-Aryl-3,5-dialkoxycarbonyl-2,6-dimethyl-1,4-dihydropyridines are brominated by N-bromosuccinimide in methanol at room temperature at the methyl groups at positions 2 and 6 to form mono-, di-, tri-, and tetrabromo derivatives. When the N-unsubstituted bromomethyl-1,4-dihydropyridines are heated they are easily converted to tetrahydrofuropyridines, but in the case of the analogous N-substituted-1,4-dihydropyridines cyclization does not occur. The 2,6-bis(bromomethyl)-substituted products easily replace bromine under the influence of nucleophilic reagents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1230–1235, September, 1991.     

Direct synthesis of 4,4-disubstituted N-silyl-1,4-dihydropyridines

An unprecedented method for the preparation of 4,4-disubstituted 1,4-dihydropyridines is presented. It is based on the trapping reaction of 4-substitued N-silylpyridinium ions. When performed with dialkylmagnesium reagents, such as iPr₂Mg, silyl protected 4,4-disubstituted 1,4-dihydropyridines were obtained in up to quantitative yields. High 1,4-selectivity was found for sterically demanding nucleophiles, whereas small nucleophiles (Me₂Mg) tend to yield 1,2-addition-products. Grignard, dialkylzinc and organocopper reagents were found to give either no addition products or less favorable results. Reduction of the obtained 1,4-dihydropyridine with NaCNBH₃ in the presence of HCl, followed by treatment with tert-butyl dicarbonate provided the corresponding N-Boc protected piperidines with high yields.     

Synthesis and electrochemical oxidation of 1-aryl-3,5-diethoxycarbonyl-2,6-unsubstituted 1,4-dihydropyridines

The possibility of obtaining 1-aryl-3,5-diethoxycarbonyl-2,6-unsubstituted 1,4-dihydropyridines with electronacceptor substituents in the N-phenyl radical was demonstrated. The intermediate products of their formation, viz., 2,4-bis(arylaminomethyiene)-3-phenylglutaric acid esters, were established. The electrochemical oxidation potentials of 1-aryl-2,6-unsubstituted 1,4-dihydropyridines are 100–200 mV higher than those of the 2,6-dimethyl analogs. A linear correlation between the electrochemical oxidation potentials and the Taft ⁰ constants of the substituents in the 1-phenyl ring was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 373–377, March, 1991.     

Synthesis of novel unsymmetrical coumarinyl-1,4-dihydropyridines

The novel unsymmetrical 3,5-dialkoxycarbonyl-2,6-dimethyl-4-(7′,8′-dimethoxycoumarin-4′-yl)-1,4-dihydropyridines and 5-acetyl-3-alkoxycarbonyl-2,6-dimethyl-4-(7′,8′-dimethoxycoumarin-4′-yl)-1,4-dihydropyridines (coumarinyl-1,4-dihydropyridines) have been synthesized by Knoevenagel condensation of 4-formyl-7,8-dimethoxycoumarin with alkyl acetoacetates in the presence of AlCl₃ followed by cyclization of the resulted Knoevenagel product with other alkyl acetoacetate or acetyl acetone and ammonium acetate. The structure of the intermediate Knoevenagel product and the cyclized unsymmetrical coumarinyl-1,4-dihydropyridines has been established on the basis of their spectral data analysis and single-crystal X-ray diffraction analysis. The observed conformation of the coumarinyl-1,4-dihydropyridines holds the key to promising calcium antagonistic activity of the synthesized coumarinyl-1,4-dihydropyridines.     

Oxidation of cationic 1,4-dihydropyridine derivatives as model compounds for putative gene delivery agents

A new synthetic approach to cationic pyridine derivatives is described here. Two different strategies for the synthesis of 1,1′-{[3,5-bis(ethoxycarbonyl)-4-phenylpyridine-2,6-diyl]dimethylene}bispyridinium salts have been developed. The key step of the first strategy relies on electrochemical and chemical oxidation of cationic 1,4-dihydropyridines; the second one involves nucleophilic substitution of pyridine dibromo derivatives.     

Synthesis and characterization of new unsaturated polyesters and copolyesters containing azo groups in the main chain

A new interesting class of linear unsaturated polyesters based on dibenzylidenecycloalkanones have been synthesized by interfacial polycondensation of 4,4^′-azodibenzoyl chloride or 3,3^′-azodibenzoyl chloride with: 2,5-bis(p-hydroxybenzylidene)cyclopentanone I, 2,6-bis(p-hydroxybenzylidene)cyclohexanone II, 2,6-divanillylidenecyclohexanone III, or 2,7-bis(p-hydroxybenzylidene)cycloheptanone IV at ambient temperature. The copolyesters are also synthesized from the monomers I, II, III or IV with the diacid chlorides. The resulting polyesters and their copolyesters were characterized by elemental analyses, IR spectroscopy and solubility. Additionally, inherent viscosity of the polyesters in the range 0.32-0.86 dL g⁻¹ and the inherent viscosity of the copolyesters in the range 0.28-0.65 dL g⁻¹ were determined. The UV-visible spectra of certain polymers were measured in m-cresol solution and showed a characteristic absorption band at 435-473 nm due to n-π^* transition. The thermal properties of the polymers were evaluated by thermo gravimetric analysis and differential scanning calorimetry measurements and correlated with their structural units. The crystallinity of some polyesters and copolyesters were tested. In addition, the electrical properties of all polyesters and copolyesters were measured.     

Reactivity of bis-vinylphosphates obtained from imide derivatives. Synthesis of 2,6-disubstituted 1,4-dihydropyridines

The Pd-catalyzed functionalization of lactam-derived vinyl phosphates has become an important tool in the last decade for the synthesis of nitrogen-containing heterocycles. By using this method, we were able to introduce alkenyl, aryl and heteroaryl groups on bis-vinylphosphate derivatives to provide efficient access to 2,6-disubstituted 1,4-dihydropyridines.     

A convenient synthesis of substituted piperazines via aminomercuration-demercuration of diallylamines

cis and trans-2,6-Bis[bromomercuriomethyl]piperazines II which bear equal or different substituents at each nitrogen are obtained in the reaction of N-substituted diallylamines with mercury(II) acetate and aryl-amines followed by a double decomposition process with potassium bromide. Their reduction with sodium borohydride lead to the corresponding 1,4-disubstituted cis- and trans-2,6-dimethylpiperazines III. Steric factors account for the remarkable stereoselectivity observed in the preparation of compounds IIIi-IIIn in which a 3:1 cis to trans isomer ratio is found.     

THE SYNTHESES OF POLYQUINOLINES WITH 2,2''''-PYRIDYLQUINOLINE AND 2,6-DIQUINOLYLPYRIDINE AS LIGAND AND THEIR APPLICATIONS IN SOME CATALYTIC REACTIONS

The polyquinolines with 2,2'-pyridylquinoline as bidentate and 2,6-diquinolylpyridine as tridentate ligand have been prepared from 4,4-dlamino- 3,3'-dibenzoyldiphenyl ether, 4,4'-diacetyldiphenyl ether and 1,4-bis (2-acetylpyridyl-6-oxy) benzene, 2,6-diacetylpyridine, respectively. These polyquinoline-supported ligands have been used in hydrogenation and hydroformylation of olefins with some transition metal complexes.     

Supramolecular helical architecture assembled by double-helical [Ag2L2] units

A series of new sterically hindered bridged ligand 4,4^′-methylene-N,N^′-bis(phenyl-2-pyridylmethylene)-bis(2,6-dialkylanil)s was efficiently synthesized by the condensation reaction of 4,4^′-methylene-bis(2,6-disubstituted aniline) and benzoyl pyridine. They easily coordinated with Ag(I) to form Ag(I) complexes. The structure of complex [Ag₂L⁴₂][ClO₄]₂ was determined by the single X-ray crystallographic analysis, and the double-helical asymmetric unit containing two [Ag₂L⁴₂] moieties was interconnected with the adjacent unit through hydrogen bonds to form a helical supramolecular architecture.     

Spectrophotometric evidence for the existence of rotamers in solutions of some ketocyanine dyes

The existence of rotational conformers in solutions of 1,5-bis[dialkylaminophenyl]-1,4-pentadien-3-one (I) was investigated by infrared, absorption and fluorescence spectroscopy. Comparison was made with 2,5-bis{[4-(dialkylamino)phenyl]-methylene}-cyclopentanone (II) and 2,6-bis{[4-(dialkylamino)phenyl]-methylene}-cyclohexanone (III) which may be considered as rigidified analogues of I. The study in organic solvents revealed that two different conformers coexisted in solutions of I. They differ by rotation about the carbonyl-carbon quasi-single bond and, according to spectroscopic data and AM1 calculations, could be cis, cis and cis, trans isomers, the latter being found in much larger proportions.     

Engineering organic sensitizers for iodine-free dye-sensitized solar cells: red-shifted current response concomitant with attenuated charge recombination

With a new metal-free donor-acceptor photosensitizer featuring the 2,6-bis(thiophen-2-yl)-4,4-dihexyl-4H-cyclopenta[2,1-b:3,4-b']dithiophene-conjugated spacer and the tris(1,10-phenanthroline)cobalt(II/III) redox shuttle, we present a highly efficient iodine-free dye-sensitized solar cell displaying a power conversion efficiency of 9.4% measured at 100 mW cm(-2) simulated AM1.5 conditions.     

A stereospecific synthesis of (+/-)-5,8-disubstituted indolizidines and (+/-)-1,4-disubstituted quinolizidines found in poison frog skins

An efficient, high-yield stereospecific route to three (+/-)-5, 8-disubstituted indolizidines, (209B (I), 209I (II), 223J (III)) and two (+/-)-1,4-disubstituted quinolizidines (207I (IV), 233A (V)), racemates of alkaloids found in the skins of neotropical and Madagascan poison frogs is reported. The structures of the natural alkaloids were thereby established by chiral GC comparison with the exception of indolizidine 209B (I) for which a natural 209B could no longer be detected.     

Synthesis and Spin State of the Cobalt(II) Complexes with Substituted 2,6-Bis(pyrazol-3-yl)pyridine Ligands

Russian Journal of Coordination Chemistry - The direct template reactions afford the cobalt(II) complexes (I–III) with the hydroxy- and acetyl-substituted 2,6-bis(pyrazol-3-yl)pyridine...     

OXIDATIVE POLYMERIZATION OF 2,6-DISUBSTITUTED PHENOLS CATALYZED BY IRON-SALEN COMPLEX

Oxidative polymerization of 2,6-disubstituted phenols has been performed by using iron(III)-salen complex and hydrogen peroxide as catalyst and oxidizing agent, respectively. The oxidative reaction of 2,6-dimethylphenol produced the polymer along with a byproduct dimer of 3,5,3',5'-tetramethyl-4,4'-dipheno-quinone. The addition of pyridine suppressed the formation of the dimer to mainly give the polymer with molecular weight of more than 1×10⁴ in high yields. From NMR analysis, the polymer was found to consist of exclusively 1,4-oxyphenylene unit. Effects of the solvent composition, added amount and type of amine, and catalyst amount have been systematically investigated. 2-Allyl-6-methylphenol and 2,6-diphenylphenol produced the corresponding polymer under the similar polymerizaconditions, whereas the formation of C-C coupling dimer was observed in using 2,6-diisopropylphenol and 2,6-dimethoxyphenol as monomer.     

1,1,2-Trihaloalkenes and Dimeric Acetylenes from Acetylenic Tellurium Species

Reaction of 1-teliuroalk-1-ynes with bromine and iodine or with Cu(II) chloride furnishes respectively 1,1,2-trihaloalkcnes and 1,4-disubstituted 1,3-diynes.     

Synthesis of benzoates of 1,4-bis(2,5-dimethyl-4-hydroxypiperidino)-2-butene and 1,4-bis-(2,5-dimethyl-4-hydroxypiperidino)-2-butyne

1,4-Bis(2,5-dimethyl-4-hydroxypiperidino)-2-butene and 1,4-bis(2,5-dimethyl-4-hydroxypiperidino)-2-butyne (II and III) were obtained by the action of 1,4-dibromo-2-butene and 1,4-dibromo-2-butyne on the form of 2,5-dimethyl-4-piperidol (I). The benzoates (IV and V) were obtained by acylation of II and III with benzoyl chloride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 352–353, March, 1971.     

Arylidene Copolyether Sulfones. I. Synthesis and Characterization of Some New Copolyether Sulfones Containing Dibenzylidene Cyclopentanone Moieties

Abstract

New copolyether sulfones containing 2,5-bis(4-oxo-benzylidene)-cyclopentanone moieties were prepared in the conventional literature manner by condensing the dipotassium salts of 2,5-bis(4-hydroxyphenzyl- idene)cyclopentanone (I) and 2, 2-bis(4-hydroxyphenyl)propane (Bisphenol A, III) with 4,4′-dichlorodiphenyl sulfone (II), or by condensing the dipotassium salts of I with chlorine-terminated Bisphenol A-4,4′-di-chlorodiphenylsulfone copolymers (V). The resulting copolyether sulfones were confirmed by IR, viscometry, DSC measurements, thermooptical (TOA), and thermogravimetric analysis (TGA).     

Diverse reactions of 1,4-dilithio-1,3-dienes with nitriles: facile access to tricyclic Delta1-bipyrrolines, multiply substituted pyridines, siloles, and (Z,Z)-dienylsilanes by tuning of substituents on the butadienyl skeleton

Addition cyclization of 1,2,3,4-tetrasubstituted 1,4-dilithio-1,3-dienes (Type I) with four equivalents of various aromatic nitriles in the presence of hexamethylphosphoramide (HMPA) gives exclusively fully substituted pyridines in moderate to good yields. Similarly, trisubstituted pyridines can be prepared by the reaction of 2,3-dialkyl- or diaryl-substituted 1,4-dilithio-1,3-dienes (Type II) with nitriles. However, five- or six-membered-ring fused 2,3-disubstituted 1,4-dilithio-1,3-dienes (Type III) reacted with various aromatic and aliphatic nitriles without alpha-hydrogen atoms to afford tricyclic Delta1-bipyrrolines in high yields. The reaction of six-membered-ring fused 2,3-disubstituted 1,4-dilithio-1,3-diene (Type III) with 2-cyanopyridine afforded the corresponding pyridine, and no tricyclic Delta1-bipyrroline was observed. Seven-membered-ring fused dilithiodienes reacted with PhCN or trimethylacetonitrile to afford the corresponding pyridines in good yield. When 1,2,3,4-tetrasubstituted dilithio reagents (Type I) were treated with Me3SiCN, a tandem silylation/intramolecular substitution process readily occurred to yield siloles, whereas the reaction of 2,3-disubstituted dilithio reagents (Types II and III) with Me3SiCN gave rise to (Z,Z)-dienylsilanes with high stereoselectivity. These results revealed that the formation of tricyclic Delta1-bipyrrolines, pyridines, siloles, and (Z,Z)-dienylsilanes are strongly dependent on the substitution patterns of the dilithio butadienes and the nature of the nitriles employed.