Formation of Exciplexes in Films of Polyimides,Polyamides, and Polyquinazolones Derived from Aromatic and Heteroaromatic Diamines

The emission bands exchibited by films of polyimides derived from 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, hexafluoroisopropylidenedibenzene-3,3′,4,4′-tetracarboxylic dianhydride, and aromatic and heteroaromatic diamines, and also of polyamides and polyquinazolones derived from the same amines are exciplex bahnds. With polyamides, complexes in the ground state are formed. The fluorescence of the photoconductivity sensitizer Rhodamine 6G is quenched in films of these polymers by the exciplex mechanism.     

Reaction products of nitronyl nitroxyl radicals with acids

Study of the structures of compounds generated by the reactions of 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1H-imidazole-1-oxyl 3-oxide with trifluoromethanesulfonic and picric acids demonstrated that these reactions produced salts of disproportionation products of nitronyl nitroxyl.     

Kinetics and mechanism of cyclohexene hydrocarbomethoxylation catalyzed by a Pd(II) complex

The kinetics of cyclohexene hydrocarbomethoxylation catalyzed by the Pd(PPh₃)₂Cl₂-PPh₃-p-toluenesulfonic acid (TSA) is reported. The reaction is first-order with respect to cyclohexene and TSA and of order 0.5 with respect to Pd(PPh₃)₂Cl₂. The reaction rate as a function of CO pressure or methanol or PPh₃ concentration passes through an extremum. The chloride anion inhibits the reaction. A mechanism involving cationic hydride complexes as intermediates is suggested. A rate equation is set up by the quasi-steady-state treatment of experimental data.     

Stereoselective synthesis of 4-substituted 1,2,3,4,10,10a-hexahydropyrazino[1,2-<Emphasis Type="Italic">a</Emphasis>]indoles

4-Substituted 1,2,3,4-tetrahydropyrazino[1,2-a]indoles were synthesized from 2-cyanoindole. (R)-4-Methyl-1,2,3,4-tetrahydropyrazino[1,2-a]indole was obtained by the Mitsunobu reaction. Stereoselective reduction of 4-substituted 1,2,3,4-tetrahydropyrazino[1,2-a]indoles gave 4-substituted 1,2,3,4,10,10a-hexahydropyrazino[1,2-a]indoles. (4R, 10aR)-4-Methyl-1,2,3,4,10,10a-hexahydropyrazino[1,2-a]indole was synthesized.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 221–225, January, 2005.     

Carbazole-functionalized polyfluorenes: synthesis and conformational properties in chloroform solution and β-phase formation in copolyfluorene films

Novel copolyfluorenes (CPFs) containing 2.5 or 10 mol% of carbazole-2,7-diyl (2,7-Cz) or carbazole-3,6-diyl (3,6-Cz) derivatives in the backbone have been synthesized by means of palladium-catalyzed Suzuki polymerization under microwave irradiation. The structure of the CPF polymers was also modified by insertion of additional 2-ethylhexyl or carbazole, diaryloxadiazole, or triphenylamine units via 3,6-Cz or 2,7-Cz comonomer units in the side chains of polymers. The self-organization of molecules in chloroform solutions was investigated using light scattering and within a wide concentration interval. Analysis of the behavior of the CPFs showed that the synthesized copolymers have an increased equilibrium rigidity of molecules with a Kuhn segment length A = (10–15) nm. The A value decreases with the introduction of Cz-units into the macromolecule in the meta-position. It is shown that chemical structure of the CPFs and thermal treatment in the temperature range 60–150 °C have a dominant effect on the optoelectronic properties as well as on microstructures of their films.     

Reaction of dialkyl 2-aryl-4-hydroxy-4-methyl-6-oxocyclohexane-1,3-dicarboxylates with aliphatic amines

Benzylamine, phenethylamine, and homoveratrylamine reacted with dialkyl 2-aryl-4-hydroxy-4-methyl-6-oxocyclohexane-1,3-dicarboxylates at the endocyclic carbonyl group with conservation of the enolic hydroxy group to give dialkyl 4-alkylamino-2-aryl-6-hydroxy-6-methylcyclohex-3-ene-1,3-dicarboxylates. The reaction of dimethyl 4-hydroxy-4-methyl-6-oxo-2-phenylcyclohexane-1,3-dicarboxylate with tryptamine was accompanied by dehydration with formation of dimethyl 4-[2-(1H-indol-3-yl)ethylamino]-6-methyl-2-phenylcyclohexa-3,5-diene-1,3-dicarboxylate, presumably due to basic properties of the indole nitrogen atom.     

Nucleophilic substitution of hydrogen–the Boger reaction sequence as an approach towards 8-(pyridin-2-yl)coumarins

1. Download : Download high-res image (126KB)
2. Download : Download full-size image

     

Reactions of 2-Acetyl-5-hydroxy-5-methyl-3-phenylcyclohexanone and Alkyl 4-Hydroxy-4-methyl-2-oxo-6-phenylcyclohexanecarboxylates with Nucleophilic Reagents

Russian Journal of General Chemistry - A series of novel enamines, bis(enamines), benzisoxazoles, tetrahydroindazoles, benzophenone hydrazones were obtained via reactions of...