5672-87-7Relevant academic research and scientific papers
A new finding in selective Baeyer-Villiger oxidation of α-fluorinated ketones; a new and practical route for the synthesis of α-fluorinated esters
Kobayashi, Satoru,Tanaka, Hiroaki,Amii, Hideki,Uneyama, Kenji
, p. 1547 - 1552 (2007/10/03)
α-Fluorinated esters were effectively prepared by the Baeyer-Villiger oxidation of α-fluorinated ketones with m-chloroperbenzoic acid (m-CPBA) under mild conditions. The yield of the esters was influenced by the choice of solvent, base, and substituent on the aryl group of the ketones. 4-Methoxyphenyl substituted fluoroketones were oxidized almost quantitatively with m-CPBA within 10 min to 12 h at room temperature using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a cosolvent with CH2Cl2 (1:1, v/v) and aqueous buffer (KH2PO4-NaOH, pH 7.6) as an additive base. The oxidation reaction rates of α-fluorinated ketones were higher than those of the corresponding non-fluorinated ketones. The fluorine atom at α-position of fluoromethyl aryl ketones enhanced the reactivity in the Baeyer-Villiger oxidation.
Electron-withdrawing substituents decrease the electrophilicity of the carbonyl carbon. An investigation with the aid of 13C NMR chemical shifts, v(C=O) frequency values, charge densities, and isodesmic reactions to interprete substituent effects on reactivity
Neuvonen, Helmi,Neuvonen, Kari,Koch, Andreas,Kleinpeter, Erich,Pasanen, Paavo
, p. 6995 - 7003 (2007/10/03)
13C NMR chemical shifts and v(C=O) frequencies have been measured for several series of phenyl-or acyl-substituted phenyl acetates and for acyl-substituted methyl acetates to investigate the substituent-induced changes in the electrophilic character of the carbonyl carbon. Charge density, bond order, and energy calculations have also been performed. The spectroscopic and charge density results indicate that opposite to the conventional thinking, electron-withdrawing substituents do not increase the electrophilicity of the carbonyl carbon but instead decrease it. On the other hand, reaction energies of the isodesmic reactions designed show that electron-withdrawing substituents destabilize the carbonyl derivatives investigated. So, a significant ground-state destabilization of carboxylic acid esters, and carbonyl compounds in general, due to the decreased resonance stabilization, is proposed as a novel concept to explain both the increase in their reactivity and the changes in the chemical shifts and carbonyl frequencies induced by electron-withdrawing substituents.
Fluorodediazoniation in ionic liquid solvents: New life for the Balz-Schiemann reaction
Laali, Kenneth K.,Gettwert, Volker J.
, p. 31 - 34 (2007/10/03)
Drawbacks associated with the classic Balz-Schiemann reaction are eliminated in a series of examples by conducting fluorodediazoniation in ionic liquid solvents, thus opening up a new horizon for a much in demand process.
A practical and highly efficient synthesis of α-(trimethylsilyl)-difluoro-acetates
Amii,Kobayashi,Uneyama
, p. 2001 - 2003 (2007/10/03)
An efficient method for the gram scale preparation of α-(trimethylsilyl)difluoroacetates is described. The key step involves Mg(0)-promoted selective C-F bond cleavage of readily available trifluoroacetates.
TRIETHYL PHOSPHITE IN ORGANIC SYNTHESIS. A FACILE, ONE-POT CONVERSION OF ALCOHOLS INTO AMINES
Zwierzak, Andrzej
, p. 51 - 54 (2007/10/02)
General protocols for converting primary, secondary, and tertiary alcohols into the corresponding primary amines are presented.
Reactions of the Readily Accessible Electrophile, Trifluoroacetyl Triflate: A Very Reactive Agent for Trifluoroacetylations at Oxygen, Nitrogen, Carbon, or Halogen Centers
Forbus, T. R.,Taylor, S. L.,Martin, J. C.
, p. 4156 - 4159 (2007/10/02)
Trifluoroacetyl triflate (TFAT) is readily prepared in 82percent yield by the dehydration (phosphorus pentoxide) of a 2:1 mixture of trifluoroacetic acid and trifluoromethanesulfonic (triflic) acid.Reactions of this highly electrophilic trifluoroacetylating reagent with alcohols, ketones, ethers, amines, and pyridines give esters, enol esters, ether cleavage, amides, and acylpyridinium ions, respectively.Reactions with ionic or easily ionizable alkyl halides give the very volatile trifluoroacetyl halides and the ionic triflate.Triphenylmethyl chloride, for example, is quantitatively converted to triphenylcarbenium triflate in a very convenient synthetic procedure.Trifluoroacetyl triflate is used in the synthesis of the first member of a new class of pyrylium salts, 2,6-dimethoxypyrylium triflate.
OXIDATION BY THE SALTS OF METALS. VII. PLUMBATION AND OXIDATIVE SUBSTITUTION OF AROMATIC COMPOUNDS IN THE LEAD TETRAACETATE-LITHIUM CHLORIDE SYSTEM IN THE PRESENCE OF PERFLUORINATED CARBOXYLIC ACIDS
Serguchev, Yu. A.,Davydova, V. G.,Makhon'kov, D. I.,Beletskaya, I. P.
, p. 1006 - 1011 (2007/10/02)
The oxidation of benzene and substituted benzenes PhX with electron-donating (X = CH3, OCH3) and electron-withdrawing (X = Hlg, CF3, NO2) substituents in the Pb(OAc)4-LiCl system was investigated in the presence of perfluorinated carboxylic acids RfCOOH (Rf = CF3, C6F13).The reaction leads to the plumbation, chlorination, and acyloxylation products.It was shown that the reactions take place through the formation of aryl derivatives of lead(IV) with the participation of mixed-ligand complexes of lead.The products from the plumbation of toluene (in C6F13COOH in the absence of lithium chloride) and benzotrifluoro were isolated.In trifluoroacetic acid these intermediates undergo intramolecular redox decomposition with ligand transfer.The halogenobenzenes and benzotrifluoride are oxidized selectively in the CF3COOH-Pb(IV)-LiCl system, giving the corresponding aryl chlorides with yields close to quantitative (80-90percent).
Inverse Temperature Effects and Concentration Dependent Apparent First Order Rate Constants in Complex Ion Radical Reactions
Parker, Vernon D.
, p. 123 - 130 (2007/10/02)
Ion radical reactions frequently consist of numerous coupled chemical and electron transfer equilibria prior to the rate determining step.Two consequences of this are (a) that the rates can show unusual temperature effects and (b) apparent first order rate constants can be concentration dependent.Both of these effects were found in two electrode reactions examined, the deprtonation of hexamethylbenzene cation radical in acetonitrile and the anodic asubstitution of bromine by trifluoroacetoxy during oxidation of 4-bromoanisole.In both cases inverse dependence of the reaction rates with temperature was observed and the apparent first order rate constants were dependent upon the substrate concentration.It is pointed out that these unusual temperature and concentration effects are powerful mechanism aids in the study of complex ion radical reactions.A method was developed for treating kinetic schemes in cases where concentration dependent apparent first order rate constants are observed.
