- Redox-Neutral Selenium-Catalysed Isomerisation of para-Hydroxamic Acids into para-Aminophenols
-
A selenium-catalysed para-hydroxylation of N-aryl-hydroxamic acids is reported. Mechanistically, the reaction comprises an N?O bond cleavage and consecutive selenium-induced [2,3]-rearrangement to deliver para-hydroxyaniline derivatives. The mechanism is studied through both 18O-crossover experiments as well as quantum chemical calculations. This redox-neutral transformation provides an unconventional synthetic approach to para-aminophenols.
- Chuang, Hsiang-Yu,Schupp, Manuel,Meyrelles, Ricardo,Maryasin, Boris,Maulide, Nuno
-
supporting information
p. 13778 - 13782
(2021/03/31)
-
- Selective Photoinduced Reduction of Nitroarenes to N-Arylhydroxylamines
-
We report the selective photoinduced reduction of nitroarenes to N-arylhydroxylamines. The present methodology facilitates this transformation in the absence of catalyst or additives and uses only light and methylhydrazine. This noncatalytic photoinduced transformation proceeds with a broad scope, excellent functional-group tolerance, and high yields. The potential of this protocol reflects on the selective and straightforward conversion of two general antibiotics, azomycin and chloramphenicol, to the bioactive hydroxylamine species.
- Kallitsakis, Michael G.,Ioannou, Dimitris I.,Terzidis, Michael A.,Kostakis, George E.,Lykakis, Ioannis N.
-
supporting information
p. 4339 - 4343
(2020/06/08)
-
- A general and scalable synthesis of polysubstituted indoles
-
A consecutive 2-step synthesis of N-unprotected polysubstituted indoles bearing an electron-withdrawing group at the C-3 position from readily available nitroarenes is reported. The protocol is based on the [3,3]-sigmatropic rearrangement of N-oxyenamines generated by the DABCO-catalyzed reaction of N-arylhydroxylamines and conjugated terminal alkynes, and delivers indoles endowed with a wide array of substitution patterns and topologies.
- Diana-Rivero, Raquel,García-Tellado, Fernando,Tejedor, David
-
-
- TRIFLUOROMETHOXYLATION OF ARENES VIA INTRAMOLECULAR TRIFLUOROMETHOXY GROUP MIGRATION
-
The present invention provides a process of producing a trifluoromethoxylated aryl or trifluoromethoxylated heteroaryl having the structure: (I), wherein A is an aryl or heteroaryl, each with or without subsutitution; and R1 is -H, -(alkyl), -(alkenyl), -(alkynyl), -(aryl), -(heteroaryl), - (alkylaryl), - (alkylheteroaryl), -NH-(alkyl), -N(alkyl)2, -NH-(alkenyl), -NH-(alkynyl) -NH-(aryl), -NH-(heteroaryl), -O-(alkyl), -O-(alkenyl), -O-(alkynyl), -O-(aryl), -O-(heteroaryl), -S-(alkyl), -S- (alkenyl), -S-(alkynyl), -S-(aryl), or -S-(heteroaryl), comprising: (a) reacting a compound having the structure: (II), with a trifluoromethylating agent in the presence of a base in a first suitable solvent under conditions to produce a compound having the structure: (III); and (b) maintaining the compound produced in step (a) in a second suitable solvent under conditions sufficient to produce the trifluoromethoxylated aryl or trifluormethoxylated heteroaryl having the structure: (I).
- -
-
Page/Page column 62-63
(2016/05/02)
-
- Mechanistic studies on intramolecular C-H trifluoromethoxylation of (hetero)arenes via OCF3-migration
-
The one-pot two-step intramolecular aryl and heteroaryl C-H trifluoromethoxylation recently reported by our group has provided a general, scalable, and operationally simple approach to access a wide range of unprecedented and valuable OCF3-containing building blocks. Herein we describe our investigations to elucidate its reaction mechanism. Experimental data indicate that the O-trifluoromethylation of N-(hetero)aryl-N-hydroxylamine derivatives is a radical process, whereas the OCF3-migration step proceeds via a heterolytic cleavage of the N-OCF3 bond followed by rapid recombination of a short-lived ion pair. Computational studies further support the proposed ion pair reaction pathway for the OCF3-migration process. We hope that the current study would provide useful insights for the development of new transformations using versatile N-(hetero)aryl-N-hydroxylamine synthons.
- Lee, Katarzyna N.,Lei, Zhen,Morales-Rivera, Cristian A.,Liu, Peng,Ngai, Ming-Yu
-
supporting information
p. 5599 - 5605
(2016/07/06)
-
- Trifluoromethoxylation of arenes: Synthesis of ortho- Trifluoromethoxylated aniline derivatives by OCF3 migration
-
Aryl trifluoromethoxylation by a two-step sequence of O-trifluoromethylation of N-aryl-N-hydroxylamine derivatives and intramolecular OCF3 migration is presented. This protocol allows easy access to a wide range of synthetically useful ortho-OCF3 aniline derivatives. In addition, it utilizes bench-stable reagents, is operationally simple, shows high functional-group tolerance, and is amenable to gram-scale as well as one-pot synthesis.Areaction mechanism of a heterolytic cleavage of the N-OCF3 bond followed by recombination of the resulting nitrenium ion and trifluoromethoxide is proposed for the OCF3-migration reaction.
- Hojczyk, Katarzyna N.,Feng, Pengju,Zhan, Chengbo,Ngai, Ming-Yu
-
supporting information
p. 14559 - 14563
(2015/01/09)
-
- Solvent hydrogen bonding and structural influences on the CrVI oxidation of anilines in aqueous acetic acid medium
-
The oxidation of meta- and para-substituted anilines by CrVI oxidant, imidazolium fluorochromate (IFC), in aqueous acetic acid mixtures of varying compositions in the presence of p-toluenesulfonic acid (PTS) is first order in IFC and PTS. Michaelis-Menten type kinetics is observed with all of the anilines. The IFC oxidation of 15 meta- and para-substituted anilines at 299-322 K complies with the isokinetic relationship but not to any of the linear free energy relationships. The isokinetic temperature lies within the experimental range. The rate data failed to correlate with macroscopic solvent parameters such as relative permittivity, εr, and ionizing power, Y, correlation of rate data with Kamlet-Taft solvatochromic parameters (hydrogen bond donor acidity, α, hydrogen bond acceptor basicity, β, and dipolarity/polarizability, π*) is linear which suggests that the specific solute-solvent interactions play a dominating role in governing the reactivity.
- Bhuvaneshwari,Elango
-
experimental part
p. 242 - 249
(2010/04/26)
-
- NOVEL COMPOUNDS AS AGONIST FOR PPAR GAMMA AND PPAR ALPHA, METHOD FOR PREPARATION OF THE SAME, AND PHARMACEUTICAL COMPOSITION CONTAINING THE SAME
-
The present invention relates to novel compounds accelerating the activity of Peroxisome proliferator-activated receptor gamma (PPARγ) and alpha (PPARα), processes of preparing the same, and pharmaceutical compositions containing the same as an active agent.
- -
-
Page/Page column 163-164
(2010/11/27)
-
- Effect of solvent on the rate of oxidation of substituted anilines with nicotinium dichromate in aqueous-acetic acid media
-
Mechanistic studies on the oxidation of 15 para- and meta-substituted anilines by nicotinium dichromate in water-acetic acid medium of varying mole fractions have been performed. The reaction can be characterized by the experimental rate equation, -d[oxidizing agent]/dt = Kk [substrate] [HCrO 4-]/(1 + K [substrate]) The addition of p-toluenesulfonic acid enhances the reaction. The oxidation substituted anilines at 299-322 K complies with the isokinetic relationship but not to any of the linear free energy relationships, the isokinetic temperature lies within the experimental range. Correlation of rate data with Kamlet-Taft solvatochromic parameters (α, β, π*) suggests that the specific solute-solvent interactions play a major role in governing the reactivity.
- Bhuvaneshwari,Elango
-
p. 999 - 1005
(2007/10/03)
-
- Effect of substituents on the rate of oxidation of anilines with peroxomonosulfate monoanion (HOOSO3-) in aqueous acetonitrile: A mechanistic study
-
Mechanistic studies on the oxidation of 18 meta-, para-, and ortho-substituted anilines (Ans) by HOOSO3- in aqueous acetonitrile medium have been performed. The reaction can be characterized by the experimental rate equation, -d[HSO5-]/dt = k[An][HSO5-] The addition of p-toluenesulfonic acid (TsOH) retards the reaction. The increase in the reactivity of anilines as the medium is made more aqueous is interpreted. The reaction is enhanced by electron-donating groups on the amine in the series consistent with the rate-limiting nucleophilic attack of the amine on the persulfate oxygen. The proposed mechanism involves the conversion of phenylhydroxylamine to nitrosobenzene in a fast step. The ESR study reveals the absence of free radicals in the reaction. Various attempts have been made to analyze the experimental rate constants in terms of LFER plots. Improved correlations are obtained with σ- values and the σ- form of the Yukawa-Tsuno equation.
- Meenakshisundaram, Subbiah,Selvaraju,Made Gowda,Rangappa, Kanchugarakoppal S.
-
p. 649 - 657
(2007/10/03)
-
- Electrophilic intermediate in the reaction of glutathione and nitrosoarenes
-
A kinetic study is reported of the reaction of glutathione (γ-L-glutamyl-L-cysteinylglycine, GSH) with nine substituted nitrosobenzenes (3,4-Me2 4-Me, 3,5-Me2, 3-Me, parent, 3-MeO, 4-Cl, 3-Cl, 3-NO2). Previous workers have shown that this reaction proceeds in parallel pathways, producing the appropriate N-arylhydroxylamine and GSSG or a sulfinanilide adduct ArNHS(O)G; a rapid equilibrium addition to form a common intermediate, a semimercaptal ArN(OH)SG, has also been observed. In the present study, equilibrium constants for the formation of this intermediate from ArNO and GSH have been measured by a kinetic method, and the kinetic behavior of the slower additional reactions of the semimercaptal have been examined in detail. For experiments carried out at constant pH and buffer concentration, the decay of ArN(OH)SG follows the rate law k2GSH[GSH] + k2(rearr). A comparison with product ratios previously reported shows that the bimolecular term with GSH represents the process forming ArNHOH and GSSG, while the unimolecular term represents the rearrangement to the sulfmanilide. The former process is found to be proportional to [OH-] for solutions near neutrality, is not buffer catalyzed, and has a ρ value of +1.4. This suggests a mechanism in which glutathione anion GS- reacts at the sulfur of the adduct displacing ArN-(OH) as a leaving group. The rearrangement reaction follows σ+ with a ρ+ value of -3.5 and has a rate law containing a pH-independent term and terms for catalysis by H+ and the acid component of the buffer. An 18O tracer study shows that the S=O oxygen in the sulfmanilide is derived from solvent, not the original N=O group. A mechanism is proposed with rate-limiting N-O cleavage, either uncatalyzed involving direct heterolysis with OH- as a leaving group or catalyzed by acids with H2O as the leaving group. The species produced is a cationic intermediate ArN+SG, a nitrenium ion stabilized by both the aryl ring and the directly attached sulfur atom. Aryl-stabilized nitrenium ions are commonly encountered in Bamberger-like rearrangements of hydroxylamine derivatives. The sulfur atom of PhN(OH)SG is shown to provide an approximately 106 rate acceleration for N-O cleavage in a comparison with the Bamberger rearrangement of PhNHOH.
- Kazanis, Sophia,McClelland, Robert A.
-
p. 3052 - 3059
(2007/10/02)
-
- Tandem Michael Addition-Sigmatropic Rearrangement Processes. Part 2. Construction of Cyclopropapyrroloindol-4-one (CPI) Unit of Antitumour Antibiotic CC-1065
-
Development of an alternative strategy for preparing 3-acetoxymethyl-2,3-dihydro-1-methylsulfonyl-6-methoxyindole 25 has been completed.Since 25 was an intermediate in a previous synthesis of the CPI unit 5 of the antitumour antibiotic CC-1065 1, this ach
- Toyota, Masahiro,Fukumoto, Keiichiro
-
p. 547 - 552
(2007/10/02)
-