- Improved intermolecular hydride transfer using task-specific ionic liquid: A reasonable and environmentally benign approach for the synthesis of bioactive 2H-thiopyran derivatives
-
The present study describes, for the first time, the application of 1-n-butyl-3-methylimidazolium borohydride ([bmim]BH4) as task-specific ionic liquid for highly regioselective reduction of triarylthiopyrylium salts. This method furnished a straightforwa
- Mouradzadegun, Arash,Najafi, Zeynab,Elahi, Somayeh
-
p. 624 - 629
(2015/11/17)
-
- A novel reaction of 2,4,6-triphenyl(thio)selenopyrylium salts leading to benzoyl(thio)selenophenes and 2,4,6-triphenyl(thio)selenopyrans
-
Thio- and selenopyrylium salts undergo simultaneous oxidation, leading to the corresponding benzoylselenophene or benzoylthiophene, and reduction reactions leading to 4H-selenopyran or 4H-thiopyran In the presence of water and triethylamine .
- Drevko,Bol'Shakova,Almaeva,Suchkov,Mandych,Shekhter
-
experimental part
p. 1526 - 1527
(2011/01/06)
-
- Efficient reduction of thiopyrylium salts to corresponding 2H- and 4H-thiopyrans under solvent-free condition: Regioselectivity and mechanism
-
A solvent-free reduction of 2,4,6-triarylthiopyrylium with NaBH 4/alumina is described. The regioselectivity of these reductions were compared with those obtained in solution experiments. Copyright Taylor & Francis Inc.
- Mouradzadegun, Arash,Gheitasvand, Nargess
-
p. 1385 - 1388
(2007/10/03)
-
- Substituent effects in reductions of heteroaromatic cations
-
A set of 11 each of 2,4,6-triphenylpyrylium, -thiopyrylium and -N-methylpyridinium tetrafluoroborates carrying a range of substituents in the phenyl rings were prepared. First and second wave reduction potentials were determined. For the thiopyrylium seri
- Heyes, David,Menon, Ramesh S.,Watt,Wiseman, Jake,Kubinski, Przemyslaw
-
p. 689 - 700
(2007/10/03)
-
- Study of the state of rhodium in the potassium rhodiumundecatungstosilicate/alumina system by diffuse-reflectance IR spectroscopy
-
Adsorption of CO on the catalytic system K5[SiW11RhO39]/Al2O3 was studied by diffusereflectunce IR spectroscopy. The electronic state of rhodium and thermal stability of the system in the redox cycles
- Korovchenko,Gazarov,Kustov
-
p. 1174 - 1177
(2007/10/03)
-
- Substituent effects in cyanoborohydride reductions of heterocyclic aromatic cations
-
First and second wave E1/2redn potentials have been measured by cyclic voltammetry for a set of fifteen 2,6-diphenyl-4-(X-phenyl)-pyrylium, -thiopyrylium and -N-methylpyridinium tetrafluoroborates, with X = p-CH3, -H, m-Cl, p-CF3 and m,m-(CF3)2.There are linear correlations between Hammett substituent constants and scaled potentials (E/0.05915) giving slopes of ρ = 2.59+/-0.06 (r2 = 0.9984), 2.38+/-0.07 (r2 = 0.9973) and 3.10+/-0.16 (r2 = 0.9918), respectively, for the first wave potentials.Products, rates and kinetic hydrogen isotope effects for reductions of the cations with sodium and tetrabutylammonium cyanoborohydride in acetonitrile solution have been determined.Reaction of the thiopyrylium 2 (X = H) yields kinetically controlled 54:46 mixture of the 4H- and 2H-thiopyrans.With the pyrylium ion 1 (X = H) the 4H- to 2H-ratio is 24:76 with the 2H-pyran suffering electrocyclic ring opening to 1,3,5-triphenylpentadienal.Product ratios are weakly sensitive to substituents on the 4-phenyl, with electron withdrawing groups increasing the amount of 2H-product for both thiopyryliums and pyrylium cations.Reductions are first order in cation and cyanoborohydride.For sodium cyanoborohydride and 2,4,6-triphenylpyrylium, k(25 deg C) = 65.6 dm3 mol-1 s-1 and for 2,4,6-triphenylthiopyrylium. k(25 deg C) = 16.7 dm3 mol-1 s-1, with kinetic isotope effects kBH3CN/kBD3CN) of 1.17 and 1.68, respectively.Logarithms of rate constants correlate with Hammett constants giving ρ = 1.46+/-0.06 (r2 = 0.9951) for the pyrylium series and ρ = 1.12+/-0.08 (r2 = 0.9831) for the thiopyryliums.The N-methylpyridinium ions do not react with cyanoborohydride.The X-ray crystal structure of 2,4,6-triphenyl-N-methylpyridinium tetrafluoroborate has been determined.Dihedral angles about bonds from the pyridinium ring to the 2- and 6-phenyls are larger than corresponding angles in 2,4,6-triphenylpyrylium and 2,4,6-triphenylthiopyryliums and are ascribed to relief of non-bonded interactions between the 2- and 6-phenyls and the N-methyl group.
- Beddoes, Roy,Heyes, David,Menon, Ramesh S.,Watt, C. Ian. F.
-
p. 307 - 320
(2007/10/03)
-
- CATALYTIC REDUCTION OF THIOPYRYLIUM SALTS AND THEIR CONDENSED ANALOGS
-
A method was developed for the synthesis of substituted thiacyclohexanes, thiadecalins, and perhydrothioxanthenes by reduction of thiopyrylium salts and their condensed analogs under the conditions of catalytic hydrogenation in the presence of catalysts b
- Kharchenko, V. G.,Bozhenova, O. A.,Shebaldova, A. D.
-
p. 2158 - 2162
(2007/10/02)
-