Conformational analysis of 1,2:5,6-diepithio-3,4-di-o-acetyl-hexitols

Conformational studies of acetylated open chain hexitol derivatives, possessing similar structures but differing in their configuration have been made by analysing their NMR spectra. It is shown, that the carbon chain of all three (manno-, ido-and gluco-) isomers is present in a non planar non zig-zag conformation, containing the acetoxy groups at C-3 and C-4 in a trans relation.     

Cyclische gekreuzt-konjugierte Bindungssysteme. XIV. 5,6-Dimethyl-1,2; 3,4-dibenzo- und 5,6-Dimethyl-1,2,3,4-tetraphenyl-calicen

The syntheses of 5,6-dimethyl-1,2;3,4-dibenzo- and 5,6-dimethyl-1,2,3,4-tetraphenyl-calicene and some of their physical and chemical properties are reported.     

1,2;3,4-Di-O-isopropylidene-l-galactose synthesis from its d-enantiomer

Easy procedure was devised to obtain di-O-isopropylidene-l-galactose from di-O-isopropylidene-d-galactose.     

Cyclische gekreuzt-konjugierte Bindungssysteme. XV. Cycloadditionen mit 5,6-Dimethyl-1,2;3,4-dibenzo- und 5,6-Dimethyl-1,2,3,4-tetraphenyl-calicen

Cycloaddition reactions of 5,6-dimethyl-1,2,3,4-dibenzo- and 5,6-dimethyl-1,2,3,4-tetraphenyl-calicene with diazo compounds, with dienes, and with dienophilic reagents are described.     

Amide catalysed facile isomerization of 5,6-dihydroisoquinolines: synthesis of stable 1,2-dihydroisoquinolines.

Stable 1,2-dihydroisoquinolines have been synthesized by an amide catalysed novel isomerization reaction of 5,6-dihydroisoquinolines.     

The syntheses of 4b,5a-dihydrodibenz[3,4:5,6]anthra[1,2-b]oxirene and 4b,5a-dihydro-5H-dibenz[3,4:5,6]anthra[1,2-b]azirine

The syntheses of the K-oxide and K-imine derivatives of dibenz[a,j]anthracene ( 1 ) are described. The parent hydrocarbon 1 that was obtained as a side product in the Elbs pyrolysis of (2-methyl-1-naphthyl)-1′-naphthylmethanone ( 10 ) was oxidized to 3-(2-formylphenyl)-3-phenanthrenecarboxaldehyde ( 3 ). Treatment of the dialdehyde with tris(dimethylamino)phosphine gave 4b,5a-dihydrodibenz[3,4:5,6]anthra[1,2-b]oxirene ( 4 ). Reaction of the oxirane with sodium azide followed by triethyl phosphite cyclization of the mixture of trans azido-alcohols so formed, yielded mainly 4b,5a-dihydrodibenz[3,4:5,6]anthra[1,2-b]azirine ( 5 ).     

A novel palladium-catalyzed synthesis of 1,2-dihydroquinoxalines and 3,4-dihydroquinoxalinones

Reactions of enamines, derived from 2-nitroanilines and alpha-substituted aldehydes, with carbon monoxide (6 atm) in the presence of a catalytic amount of bis(dibenzylideneacetone)palladium(0) (Pd(dba)(2)) and 1,3-bis(diphenylphosphino)propane (dppp) afford readily separated mixtures of 1,2-dihydroquinoxalines and 3,4-dihydroquinoxalinones. Addition of a catalytic amount of 1,10-phenanthroline to the reaction mixture substantially improved the yield of products. [reaction: see text]     

Synthesis and characterization of benzo[1,2-b:3,4-b':5,6-b']trithiophene (BTT) oligomers

Two dimers (2 and 3), dendritic tetramer (4), hexamer (5), and decamer (6) of benzo[1,2-b:3,4-b':5,6-b']trithiophene (BTT), a potential π-core unit with C(3h) symmetry, were synthesized, characterized, and evaluated for possible use as organic semiconductors. Single crystal X-ray analyses of the dimers (2 and 3) revealed that they have planar molecular structures with dihedral angles of almost 180° between two BTT units. In accordance with the rigid and planar molecular structure, the unsubstituted dimer (2) is poorly soluble, whereas the octyl-substituted dimer (3) has improved solubility. Although the solubility of the dendritic tetramer (4) is decreased, further extended systems, i.e., the dendritic hexamer (5) and decamer (6), have solubilities better than that of 4. With increasing numbers of BTT units in the molecule, the experimentally determined energy levels of HOMO shift upward slightly and the HOMO-LUMO energy gaps become smaller, but the extent of HOMO destabilization and reduction of the HOMO-LUMO gap are not significant. Taking into account the energy levels of the frontier orbitals, 3-6 could be useful as p-channel organic semiconductors rather than n-channel. In fact, the spin-coated thin film of 3 with edge-on molecular orientation acted as an active channel of field-effect transistors that showed hole mobilities as high as 0.14 cm(2) V(-1) s(-1), indicating that the BTT core is a useful π-conjugated system for application to organic semiconductors, although 4-6 gave FET characteristics rather inferior to those of 3, owing to their amorphous nature in the thin film state.     

On the synthesis of 3,4-dihydro-2H-1,2-benzothiazine 1,1-dioxides

The 3,4-dihydro-2H-1,2-benzothiazine 1,1-dioxides were prepared by reduction of the corresponding 1,2-benzothiazin-2-ones with diborane. The latter were obtained by the action of primary amines on 4,5-dimethoxy-2-carbomethoxymethylbenzenesulfonyl chloride followed by basic hydrolysis and cyclization of the formed 4,5-dimethoxy-2-carbomethoxymethylbenezenesulfonamides.     

Derivatives of 4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-4,9-dione: synthesis and properties

A new family of organic semiconducting materials (1-4) integrating the structural components of thiophene and fluorene into a single molecular entity was synthesized and characterized. Optical and electrochemical properties of these previously unknown 4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-4,9-dione derivatives were studied in detail. These materials possess unique optical properties with the longest wavelength absorption maxima around 500-800 nm, which gradually reached a saturation limit with the total number of thiophene units approaching eight. They also display dramatic change in the redox properties with increasing conjugation chain lengths. A thin film of oligomer 3 prepared by a solution-casting method showed a well-ordered solid-state structure according to X-ray diffraction analysis.     

RP-HPLC assay for 1,2-5,6-dianhydro-3,4-disuccinyl-galactitol and its metabolites in blood plasma and liver

Summary A method involving pre-column derivatization and HPLC assay is described for measuring submicrogram quantities of 1,2-5,6-dianhydro-3,4-disuccinyl-galactitol (1,2-5,6-dianhydro-3,4-bis(carboxypropionyl)-galactitol), an effective cytostatic drug and its metabolites in blood plasma and liver homogenate. The substance and its metabolites were derivatized with sodium pentamethylene-dithiocarbamate to form different bis(dithiocarbamoyl) esters, which can be detected by UV absorbance at 254 and 280 nm. The directly derivatized products were then extracted into CHCl₃, and after sample preparation resolved by RP-HPLC on SAS-Hypersil column.     

5,6-dihydropyridine: synthesis and characterization

5,6-dihydropyridine 1 is synthesized either by flash vacuum thermolysis of 1-azabicyclo[2.2.2] oct-2-ene 3 or by dehydrochlorination over solid bases of N-chloro-1,2,5,6-tetrahydropyridine 4 and characterized at low temperature by its ¹H and ¹³C nmr and ir spectra.     

Design and synthesis of pyrazolo[3,4-d]pyridazine 5,6-dioxides as novel NO-donors

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