52762-76-2Relevant articles and documents
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
Synthesis of functionalised furans and pyrroles through annulation reactions of 4-pentynones
Arcadi, Antonio,Rossi, Elisabetta
, p. 15253 - 15272 (2007/10/03)
A new approach to 4-pentynones through palladium-catalysed coupling reaction of the ready available 2-propynyl ketones with aryl iodides and/or vinyl triflates is proposed. Annulation reactions of both 2-propynyl ketones and 4-pentynones gave functionalised furans using potassium tert-butoxide in DMF and functionalised pyrroles in the presence of benzylamine or ammonia, respectively in good to high yields. The methodology has been extended to the preparation of 17β-hydroxyandrost-4-en[3,2-b](5-methyl)furan and to 17β- hydroxyandrost-4-en[3,2-b](1-benzyl-5-methyl)pyrrole. A different reaction pattern was observed when the 4-pentynones were treated with sodium methoxide in MeOH. The influence of the reaction medium on the outcome of the annulation reaction in the case of one 2-pentyn-1,6-dione (heteroannulation vs. carbocyclization) is also shown.
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.
