5306-98-9Relevant academic research and scientific papers
Process for the preparation of phenols
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Paragraph 0024, (2017/01/12)
The present invention relates to a process for the preparation of phenols in which an aryldiazonium salt, which is prepared by the diazotization of a corresponding aromatic, primary amine, by heating in a mixture comprising hot water, a mineral acid and an organic solvent, is decomposed, where the organic solvent comprises a ketone of the formula (I) R1C(O)R2, in which R1 and R2, independently of one another, are (C1-C5)-alkyl and R1 and R2 together have at least four carbon atoms, where the aromatic primary amine is aniline or a substituted aniline which comprises at least one further substituent which is selected from: alkyl, alkenyl, alkynyl, halogen, haloalkyl, cycloalkyl, heteroalkyl, carboxyl, cyano, alkoxy and ester, and where essentially no copper salts are present in the mixture.
Copper-catalyzed C-N bond cross-coupling of aryl halides and amines in water in the presence of ligand derived from oxalyl dihydrazide: Scope and limitation
Kurandina,Eliseenkov,Khaibulova,Petrov,Boyarskiy
, p. 7931 - 7937 (2015/09/15)
An efficient and convenient method has been developed for the copper-catalyzed C-N bond cross-coupling of aryl bromides with electron-donor substituents and aliphatic amines in water. The new ligand system N-phenyloxalyl bishydrazide/hexane-2,5-dione has been shown to be considerably more efficient in the copper-catalyzed C-N bond cross-coupling reaction as compared to the ligands described in the literature and allowed decreasing of the catalyst amount (up to 2 mol %) to achieve acceptable yields of isolated products (46-84%). Acceptor substituted aryl bromides, aryl bromides with substituents in the ortho-position, and some aryl dichlorides can undergo the C-N cross-coupling under the developed conditions, but their reactivity is lower.
Oxidation of p-chlorotoluene and cyclohexene catalysed by polymer-anchored oxovanadium(iv) and copper(ii) complexes of amino acid derived tridentate ligands
Maurya, Mannar R.,Kumar, Maneesh,Kumar, Amit,Pessoa, Joao Costa
experimental part, p. 4220 - 4232 (2009/02/03)
3-Formylsalicylic acid (Hfsal), covalently bound to chloromethylated polystyrene (PS) and cross-linked with 5% divinylbenzene reacts with d,l-alanine and l-isoleucine to give the Schiff-base tridentate ligands PS-H 2fsal-d,l-Ala and PS-H2fsal-l-Ile, respectively. These anchored ligands upon reaction with VOSO4 and Cu(CH 3COO)2?H2O form the complexes PS-[VO(fsal-d,l-Ala)(H2O)], PS-[Cu(fsal-d,l-Ala)(H2O)], PS-[VO(fsal-l-Ile)(H2O)] and PS-[Cu(fsal-l-Ile)(H2O)]. The structures of these immobilized complexes have been established on the basis of scanning electron micrographs, spectroscopic (infrared, electronic and EPR), thermogravimetric and elemental analysis studies. The oxidation of p-chlorotoluene and cyclohexene has been investigated using these complexes as the catalysts in the presence of H2O2 as the oxidant. Reaction conditions have been optimised by considering the concentration of the oxidant, the amount of catalyst used and the temperature of the reaction mixture. Under the optimised conditions, p-chlorotoluene gave a maximum of 14% conversion using PS-[VO(fsal-d,l-Ala)(H2O)] as the catalyst, with the main products having a selectivity order of: p-chlorobenzaldehyde >> p-chlorobenzylalcohol > p-chlorobenzoic acid > 2-methyl-5-chlorophenol > 3-methyl-6-chlorophenol. The oxidation of cyclohexene with PS-[VO(fsal-d,l-Ala)(H2O)] proceeds with 79% conversion, which is followed by PS-[VO(fsal-l-Ile)(H2O)] with 77% conversion, and the oxidation of cyclohexene by Cu-based catalysts occurs with considerably lower conversions (29-32%). The selectivity of the products follows the order: 2-cyclohexene-1-ol > cyclohexene oxide > cyclohexane-1,2-diol > 2-cyclohexene-1-one. Recycling studies indicate that these catalysts can be reused at least three times without any significant loss in their catalytic potential. However, EPR studies indicate that while the polymer supported V(iv)O-complexes do not change after being used, the EPR spectra of the Cu-complexes show significant changes. The corresponding non-polymer bound complexes [VO(fsal-d,l-Ala)(H2O)], [Cu(fsal-d,l-Ala)(H 2O)], [VO(fsal-l-Ile)(H2O)] and [Cu(fsal-l-Ile)(H 2O)] have also been prepared in order to compare their spectral properties and catalytic activities. The non-polymer bound complexes exhibit lower conversion, along with lower turn-over frequency as compared to their polymer-bound analogues. Several EPR, 51V NMR and UV-vis studies have been undertaken to detect the intermediate species, and outlines for the mechanisms of the catalytic reactions are proposed.
Oxidation of benzyl radicals by Fe(CN)63-
Merga, Getahun,Schuchmann, Heinz-Peter,Rao, B. S. Madhava,Von Sonntag, Clemens
, p. 551 - 556 (2007/10/03)
Hydroxyl radicals and their anions [O?- radicals, pK a(?OH) = 11.9] have been generated radiolytically in N2O-saturated aqueous solution and reacted with 4-chlorotoluene. While the ?OH radical mainly produces hydroxycyclohexadienyl- type radicals, the O?- radical practically only abstracts H atoms from the methyl group yielding 4-chlorobenzyl radicals (k = 1.9 x 10 9 dm3 mol-1 s-1; determined by pulse radiolysis). The radicals formed by ?OH radical attack at pH 7 (mainly hydroxycyclohexadienyl-type radicals) are oxidized by Fe(CN) 63- (k = 1.8 x 107 dm3 mol -1 s-1) giving rise to the following products (G values in units of 10-7 mol J-1 are given in parentheses): 4-chloro-2-hydroxytoluene (2.9), 4-chloro-3-hydroxytoluene (2.4), 4-chlorobenzyl alcohol (0.05), 4-chlorobenzaldehyde (0.1) and 4-chloro-2-hydroxybenzaldehyde (0.15). The 4-chlorobenzyl radical is the main species formed at pH 13.7 and is oxidized by Fe(CN)63- with a similar rate constant (k = 4.2 x 107 dm3 mol-1 s-1), the major products being 4-chlorobenzaldehyde (3.7), 4-chloro-2-hydroxybenzaldehyde (0.65) and 4-chlorobenzyl alcohol (0.5). From ?OH radical attack (ca. 10% at this pH), 4-chloro-2-hydroxytoluene (0.4) and 4-chloro-3-hydroxytoluene (0.3) are also formed. It is suggested that the oxidation of the 4-chlorobenzyl radical by Fe(CN)63- yields in the first step a carbocation which cyclizes by deprotonation. The resulting cyclohexadienyl-type radical undergoes β-fragmentation yielding the 4-chlorobenzyloxyl radical. A 1,2-H shift and subsequent oxidation leads to 4-chlorobenzaldehyde. The unsubstituted benzyl radical is also oxidized by Fe(CN)63- yielding benzaldehyde in high yields.
Single Step Selective Oxidation of para-Chlorotoluene to para-Chlorobenzaldehyde over Vanadium Silicate Molecular Sieves
Selvam, T.,Singh, A. P.
, p. 883 - 884 (2007/10/02)
Selective formation of para-chlorobenzaldehyde (> 65percent) in a single step from para-chlorotoluene is reported for the first time using H2O2 as an oxidant and vanadium silicate molecular sieves as the catalyst.
Reactions of OH and SO4.- with Some Halobenzenes and Halotoluenes: A Radiation Chemical Study
Merga, Getahun,Rao, B. S. M.,Mohan, H.,Mittal, J. P.
, p. 9158 - 9164 (2007/10/02)
The optical absorption and kinetic characteristics of the transients formed in the reactions of OH and SO4.- with bromobenzene, ortho and meta-isomers of chloro- and bromobenzenes, and monobromotoluenes have been studied by pulse radiolysis technique.The rates for OH reaction are generally higher (k = (1.7-4.4)X109 M-1s-1) than those found for the SO4.- reaction (k = (0.4-2.3)x109 M-1s-1). ρ+ values of -0.4 for OH and -1.2 for SO4.- reactions were obtained from the Hammett analysis.The formation of substituted hydroxycyclohexadienyl radicals (λmax = 315-330 nm) is the major reaction channel, and the phenoxyl type radical (λ >/=400 nm) formation is an additional minor process in the SO4.- reaction.Abstraction of H by SO4.- from the -CH3 group is only significant with the para-isomers of bromo- and chlorotoluenes.This result is in accord with the observed yields (70 percent of SO4.-) of the products resulting from the oxidation of the 4-chlorobenzyl radical in the presence of K3Fe(CN)6 under steady-state conditions.The total yields of the phenolic products accounting for >90 percent of OH and SO4.- suggest that the attack at the ipso positions is considerably small.The rate constants for OH reactions relative to benzene at positions 3 and 6 of 2-chlorotoluene and positions 2 and 3 of 4-chlorotoluene are between 1.18 and 1.39, indicating that the directing effects of -CH3 and -Cl groups are comparable.This is also reflected in the additive effects of activation of the ortho and para-positions and deactivation of meta-positions by these substituents in 3-chlorotoluene.
Electrophilic Aromatic Substitution. Part 30. The Kinetics and Products of the Solvolyses in Aqueous Sulphuric Acids of 5-Chloro-2-methyl-2-nitrocyclohexa-3,5-dienyl Acetate: the Occurence of AAC2 and AAl1 Solvolyses, and of an Acid-catalysed Elimination of Nitrous Acid, and the...
Bloomfield, Colin,Moodie, Roy B.,Schofield, Kenneth
, p. 1793 - 1802 (2007/10/02)
Good first order kinetics of solvolysis of the above-named diene in water and in 6.5-43.6percent H2SO4 at 25 deg C, and in water and in 15.2-58.8percent H2SO4 at 5 deg C have been observed.The yields of 4-chlorotoluene, 5-chloro-2-methylphenyl acetate, 5-chloro-2-methylphenol, 4-chloro-2-nitrotoluene, 4-chloro-3-nitrotoluene, and 4-methyl-2-nitrophenol produced in water and in 21.5-92.4percent H2SO4 at 25 deg C in the presence of sulphanilic acid or hydrazinium sulphate, and additionally of 2- and 4-nitroanisole when anisole was also added, have been measured.The solvolysis proceeds by an acid-catalysed elimination of nitrous acid (confirming a tentative conclusion in another case), which competes with AAC2 and AAL1 ester solvolyses.With increasing acidity the solvolyses become dominant, the AAL1 reaction increasingly so.The small yield of 4-chloro-3-nitrotoluene comes from a thermal reaction of the diene unrelated to the elimination and solvolyses.The AAL1 reaction generates the ipso-Wheland intermediate (WiMe) that is also formed in the nitration of 4-chlorotoluene.The intermediate reacts by return to 4-chlorotoluene and nitronium ion (which can be captured by anisole), by 1,2-and 1,4-nucleophilic capture by water (giving 5-chloro-2-methylphenol and 4-methyl-2-nitrophenol, respectively), and by 1,2-rearrangement to 4-chloro-2-nitrotoluene.The first of these reactions never accounts for more than about 12percent of the WiMe and competition between capture and rearrangement moves strongly in favour of the latter with increasing acidity.Re-examination of the nitration of 4-chlorotoluene has revealed products arising from 1,2- and 1,4-capture of WiMe, previously overlooked.An improved assessmentof positional reactivities shows 59percent of primary attack by nitronium ion to occur at C-Me in 63percent H2SO4.
THE REACTIONS OF UNACTIVATED ARYL HALIDES WITH SODIUM METHOXIDE IN HMPA; SYNTHESIS OF PHENOLS, ANISOLES, AND METHOXYPHENOLS
Testaferri, L.,Tiecco, M.,Tingoli, M.,Chianelli, D.,Montanucci, M.
, p. 193 - 198 (2007/10/02)
Sodium methoxide reacts with dichlorobenzenes in HMPA to give the chloroanisoles as a result of a SNAr process.Excess MeONa then effects the demethylation of the ethers to give the chlorophenols via an SN2 reaction.With tri- and tetrachlorobenzenes the initially formed chloroanisoles can be dealkylated to chlorophenols or can suffer further substitution to give the chlorodimethoxybenzenes; these react with excess MeONa to give the chloromethoxyphenols.The results obtained with the various isomers of the di-, tri-, and tetrachlorobenzenes are presented and discussed on the basis of the electronic effects of the substituents.
