801-06-9Relevant academic research and scientific papers
Facile and Stereospecific Synthesis of Various Dienones Using Task-specific Ionic Liquid/Borohydride as Stable and Promoted Hydrogen Release Reagent
Mouradzadegun, Arash,Ganjali, Mohammad Reza,Sabbagh, Elham,Abadast, Fatemeh
, p. 3574 - 3577 (2017/11/21)
In this work, for the first time, task-specific ionic liquid, 1-n-butyl-3-methylimidazolium borohydride ([bmim]BH4), was used as the medium as well as reagent for the regiospecific reduction of triarylpyrylium perchlorates to provide aromatic d
Substituent effects in reductions of heteroaromatic cations
Heyes, David,Menon, Ramesh S.,Watt,Wiseman, Jake,Kubinski, Przemyslaw
, p. 689 - 700 (2007/10/03)
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
Substituent effects in cyanoborohydride reductions of heterocyclic aromatic cations
Beddoes, Roy,Heyes, David,Menon, Ramesh S.,Watt, C. Ian. F.
, p. 307 - 320 (2007/10/03)
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.
SYNTHESIS OF 4H-PYRANS BY O-CYCLIZATION OF 1,5-DIKETONES
Blinokhvatov, A. F.,Markovtseva, O. V.,Nikolaeva, M. N.
, p. 266 - 268 (2007/10/02)
Substituted 4H-pyrans were obtained in high preparative yields by the reaction of 1,5-diketones with acetic anhydride and boron trifluoride etherate in diethyl ether.It is assumed that the heterocyclization of 1,5-diketones includes a step involving the f
Δ3-DIHYDROPYRANS AND TETRAHYDROPYRANS BY REDUCTION OF PYRYLIUM SALTS WITH SODIUM BOROHYDRIDE IN ACETIC ACID
Balaban, Teodor-Silviu,Balaban, Alexandru, T.
, p. 1341 - 1344 (2007/10/02)
The major reduction products with triacetoxyborohydride (NaBH4 in AcOH) of 2,4,6-trisubstituted pyrylium salts bearing alkyl substituents in the 2- and/or 6-position are the Δ3-dihydropyrans with cis 2- and 6-substituents and all-cis-2,4,6-trisubstituted tetrahydropyrans. Δ3-dihydropyrans are shown to be formed via 2H-pyrans by a 1,4 reduction while tetrahydropyrans result from 4H-pyrans by reduction of both enol-ether double bonds.
