- o-directed lithiation of acylated hydroxythiophenes
-
O-Carbamates derived from 2-hydroxy- and 3-hydroxy-thiophenes generated o-directed carbanions, which were transformed to the corresponding methyl sulfides and methyl and trimethylsilyl substituted thiophenes.
- Vendina, Ineta,Parkova, Anete,Trapencieris, Peteris
-
-
Read Online
- Hemicucurbit[6]uril-induced aerobic oxidation of heterocyclic compounds
-
The aerobic oxidation of furan in aqueous solution in the presence of HemiQ[6] has been investigated, and the product furan-2,5-diol is stabilized by encapsulation of HemiQ[6], which could be transformed to the dione confirmation in acidic solution and escape from the macrocyclic compound. The 1H NMR titration experiments of the host-guest interaction at different pH values suggest protonation should improve the encapsulation, and therefore an unique property that HemiQ[6] can be protonated has been revealed. The oxidizing kinetics suggests that the procedure is a consecutive reaction with a series of constants k1 = 2.9 × 10-2 min-1, k 2 = 2.7 × 10-2 min-1, and k3 = 5.7 × 10-3 min-1, respectively. The kinetic investigation at pD = 2.0 indicates the HemiQ[6]-catalytic oxidation of furan could be accelerated by acidification. As a consequence, a plausible mechanism has been established on the above evidences. 2-Methylfuran is employed to give the product 2-methylfuran-5-ol exhibiting a satisfied activity in this aerobic oxidation with the supramolecular catalysis of HemiQ[6], but the oxidation of thiophene is very slow in either neutral or acidic condition.
- Cong, Hang,Yamato, Takehiko,Tao, Zhu
-
-
Read Online
- BIARYL HYDROXYTHIOPHENE GROUP IV TRANSITION METAL POLYMERIZATION CATALYSTS WITH CHAIN TRANSFER CAPABILITY
-
Catalyst systems that include a chain transfer agent and a metal-ligand complex according to formula (I).
- -
-
-
- BIARYL PHENOXY GROUP IV TRANSITION METAL CATALYSTS FOR OLEFIN POLYMERIZATION
-
Embodiments are directed to catalyst systems comprising at least one metal ligand complex and to processes for polyolefin polymerization incorporating the catalyst systems. The metal ligand complexes have the following structures:
- -
-
-
- An efficient base and H2O2 free protocol for the synthesis of phenols in water and oxygen using spinel CuFe2O4 magnetic nanoparticles
-
An efficient base and H2O2 free protocol was used for the synthesis of phenols from boronic acids using biogenic CuFe2O4 magnetic nanoparticles as catalyst at room temperature in water and oxygen. The catalyst was prepared using the flowers of Lantana camara. The size of the nanoparticles was 4.27 nm. Base free and ligand free protocol, less time, excellent yields, room temperature, biogenic synthesis of the catalyst, use of O2 as an environmentally friendly oxidant are the advantages of the present protocol. The recyclability of the catalyst was for 5 cycles without loss of magnetic property or catalytic activity.
- Chutia, Rituparna,Chetia, Bolin
-
p. 1925 - 1936
(2020/08/13)
-
- Trinuclear Mn2+/Zn2+based microporous coordination polymers as efficient catalysts foripso-hydroxylation of boronic acids
-
Two microporous coordination polymers based on hourglass trinuclear building units, [Mn3(bpdc)3(bpy)]·2DMF and [Zn3(bpdc)3(bpy)]·2DMF·4H2O (bpdc = 4,4′-biphenyl dicarboxylic acid, bpy = 4,4′-bipyridine), have been synthesized under solvothermal conditions employing DMF as the solvent. Each structure consists of two crystallographically distinct M2+(M1 and M2) centers that are connectedviacarboxylate bridges from six bpdc ligands, generating a trinuclear metal cluster, [M3(bpdc)3(bpy)]. Cluster representation of the structure resulted in an interpenetrated net of rarehextopological type. Catalytic activities of the CPs have been assessed for the oxidative hydroxylation of phenylboronic acids (PBAs) using aqueous hydrogen peroxide (H2O2). Various substituted aryl/hetero-arylboronic acids RB(OH)2[R = phenyl, 2,4-difluorophenyl, 4-aminophenyl, 2-thiopheneetc.] underwentipso-hydroxylation smoothly at room temperature to generate the corresponding phenols in excellent yields. The main advantages of this protocol are the aqueous medium reaction, heterogeneous catalytic system, and short reaction time with excellent yield.
- Bora, Sanchay J.,Dutta, Anurag,Goswami, Shyam,Guha, Ankur K.,Paul, Rima,Thakur, Ashim J.
-
p. 5454 - 5462
(2020/05/16)
-
- A simple, fast and excellent protocol for the synthesis of phenols using CuFe 2O 4 magnetic nanoparticles
-
Abstract: This paper describes a very mild, quick and simple protocol for the synthesis of phenols using CuFe 2O 4 magnetic nanoparticles as a catalyst. The nanosized catalyst has an average diameter of 17.63 nm. The magnetic nanoparticles were characterized by SEM, EDX, VSM, XRD and TEM analysis. The synthesis of phenols from phenylboronic acids using H 2O 2 as an oxidant proceeded very well with excellent yields. Heterogeneous catalyst, easy recyclability, mild reaction conditions, short reaction time added as an advantage for the present protocol. Graphical Abstract: A very mild, quick and efficient protocol has been designed for the preparation of phenols from phenyl boronic acids using CuFe 2O 4 Magnetic Nanoparticles (MNPs) as a catalyst. Heterogeneous catalyst, easy recyclability added as an advantage for the protocol.[Figure not available: see fulltext.].
- Chutia, Rituparna,Chetia, Bolin
-
-
- Cellulose as recyclable organocatalyst for ipso-hydroxylation of arylboronic acids
-
Cellulose catalyzed oxidative hydroxylation of aryl and hetero-arylboronic acids to the corresponding phenols under metal and base free strategy has been demonstrated. The sustainable ipso-hydroxylation takes place using hydrogen peroxide as an oxidant in water under mild condition in shorter period of time. Interestingly, easy recovery and reusability of heterogeneous catalyst without significant loss in catalytic yield makes the protocol environmentally benign.
- Laskar, Khairujjaman,Paul, Subham,Bora, Utpal
-
-
- Heterogeneous Palladium–Chitosan–CNT Core–Shell Nanohybrid Composite for Ipso-hydroxylation of Arylboronic Acids
-
Abstract: A novel palladium-nanohybrid (Pd–Chitosan–CNT) catalytic composite has been developed using CNT–chitosan nanocomposite and palladium nitrate. The prepared catalytic platform displays excellent catalytic reactivity for the ipso-hydroxylation of various arylboronic acids with a mild oxidant aqueous H2O2 at room temperature, affording the corresponding phenols in excellent yields. Significantly, the easy recovery and reusability by simple manipulation demonstrate the green credentials of this catalytic platform. Graphical Abstract: [Figure not available: see fulltext.]
- Shin, Eun-Jae,Kim, Han-Sem,Joo, Seong-Ryu,Shin, Ueon Sang,Kim, Seung-Hoi
-
-
- Size-tunable ZnO nanotapes as an efficient catalyst for oxidative chemoselective C–B bond cleavage of arylboronic acids
-
Herein, we report a simple but effective chemical approach for the synthesis of size-tunable ZnO nanotapes by precipitation method in the presence of phytochemicals present in the flower extract of Lantana camara plant. The electron microscopic study confirmed that the size of ZnO nanotapes can be systematically controlled by varying the concentration of either flower extract or metal ions and the flower extract played the key role in controlling the growth of ZnO nanotapes. The phase and crystalline analysis was carried out by X-ray diffraction method which indicated that ZnO nanostructures are highly crystalline in nature and are free from any impurities. The synthesized ZnO nanostructures exhibited interesting optical properties as investigated by UV–vis absorption and photoluminescence spectroscopy. Further the surface functionalities affect the optical properties of ZnO nanostructures which possess relatively strong UV emissions; a blue emission and a green emission. The synthesized ZnO nanostructures showed excellent catalytic properties in the ipso-hydroxylation of different aryl/ hetero-arylboronic acid to phenol in a relatively greener reaction conditions. These catalysts are highly stable and are re-usable upto six cycles of ipso-hydroxylation without losing its catalytic properties.
- Phukan, Shreemoyee,Mahanta, Abhijit,Rashid, Md. Harunar
-
-
- Chemoselective oxidation of aryl organoboron systems enabled by boronic acid-selective phase transfer
-
We report the direct chemoselective Brown-type oxidation of aryl organoboron systems containing two oxidizable boron groups. Basic biphasic reaction conditions enable selective formation and phase transfer of a boronic acid trihydroxyboronate in the presence of boronic acid pinacol (BPin) esters, while avoiding speciation equilibria. Spectroscopic investigations validate a base-promoted phase-selective discrimination of organoboron species. This phenomenon is general across a broad range of organoboron compounds and can also be used to invert conventional protecting group strategies, enabling chemoselective oxidation of BMIDA species over normally more reactive BPin substrates. We also demonstrate the selective oxidation of diboronic acid systems with chemoselectivity predictable a priori. The utility of this method is exemplified through the development of a chemoselective oxidative nucleophile coupling.
- Molloy, John J.,Clohessy, Thomas A.,Irving, Craig,Anderson, Niall A.,Lloyd-Jones, Guy C.,Watson, Allan J. B.
-
p. 1551 - 1559
(2017/02/10)
-
- Novel CuCl2-cryptand-[2.2.Benzo] complex: A base free and oxidant free catalyst for Ipso-Hydroxylation of aryl/heteroaryl-boronic acids in water at room temperature
-
A novel cryptand and its copper complex was synthesised, which found to have enormous catalytic activity towards ipso-hydroxylation of aryl or heteroarylboronic acids and esters in water without using H2O2 or other oxidising agent and base at room temperature. This newly developed method efficiently converts aryl boronic acids and esters as well as heteroaryl boronic acids to their corresponding phenols with high yields within a very short reaction time. This protocol has found to be well-matched with a wide variety of functional groups. High yields, very short reaction time, easy separation, recyclability up to 6th time are the advantages of this method.
- Bora, Sankar Jyoti,Chetia, Bolin
-
supporting information
p. 52 - 56
(2017/09/19)
-
- Banana pulp extract mediated synthesis of Cu2O nanoparticles: An efficient heterogeneous catalyst for the ipso-hydroxylation of arylboronic acids
-
A green and facile novel procedure has been developed for the synthesis of Cu2O nanoparticles within a very short reaction time using banana pulp extract as a reducing agent. The synthesized nanoparticles are well characterized by SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) and powder XRD (X-ray Diffraction) methods. An environmental benign and highly efficient protocol for the ipso-hydroxylation of aryl and hetero arylboronic acids using bio-fabricated Cu2O nanoparticles as a catalyst and aqueous H2O2as an oxidant has also been developed. The main advantages of this protocol are the base free reaction condition, reusable and heterogeneous catalytic system, and short reaction time with excellent yields.
- Borah, Rupom,Saikia, Eramoni,Bora, Sankar Jyoti,Chetia, Bolin
-
p. 1211 - 1215
(2017/03/02)
-
- Ipso-hydroxylation of aryl/heteroarylboronic acids using WEBPA as a green catalyst
-
Background: As the phenols and its derivatives are considered as versatile precursors, herbicides, drugs and antioxidants, the synthesis of phenols has been gaining much attention during the last decades. Despite the numerous methods for phenol synthesis there is a serious need for "green" protocols with greater environmental benign and economic viability. Method: We used a highly abundant and inexpensive natural feedstock WEBPA (Water Extract of Banana Peel Ashes) with 30% aqueous H2O2 as an oxidant for the synthesis of phenol and its derivatives. Results: Ipso-hydroxylation of twelve different types aryl and hetero aryl boronic acids with both electron donating and electron withdrawing groups such as OMe, Me, Cl, NO2, COMe etc. has been carried out by the newly developed protocol with excellent yields in a short period of time. The catalytic system has also been found effective up to 5th cycle without significant loss of activity. Conclusion: In conclusion, we have developed a reusable, mild, and efficient protocol for the ipso-hydroxylation of aryl/heteroarylboronic acids. This protocol seems to be one of the greenest and economic alternatives to the existing protocol.
- Saikia, Eramoni,Chetia, Bolin,Bora, Sankar Jyoti
-
supporting information
p. 764 - 769
(2017/02/05)
-
- On-water synthesis of phenols using biogenic Cu2O nanoparticles without using H2O2
-
In recent years the biogenic synthesis of metal oxide nanoparticles using natural resources has received significant attention due to their easy availability, low cost and environmentally benign protocol. In this study, Cu2O nanoparticles have been synthesised using Syzygium jambos (L.) Alston plant extracts without using toxic chemicals. The average size of the nanoparticles is 7.6 nm which found to have excellent catalytic activity in the ipso-hydroxylation of arylboronic acids without using H2O2. Mild reaction condition, excellent yield, easy separation and reusability of the catalyst are the advantages of this method.
- Borah, Rupom,Saikia, Eramoni,Bora, Sankar Jyoti,Chetia, Bolin
-
p. 100443 - 100447
(2016/11/09)
-
- H2O2 in WERSA: An efficient green protocol for ipso-hydroxylation of aryl/heteroarylboronic acid
-
A mild, green, economic and efficient protocol has been developed for ipso-hydroxylation of aryl/heteroarylboronic acids to phenols using 30% aqueous H2O2 as an oxidant and WERSA (water extract of rice straw ashes) as a neat reaction medium. All reactions were carried out without using metal, ligand, activator or hazardous organic solvent with excellent yield within a very short reaction time at room temperature. Therefore, this appears to be the cleanest and greenest alternative protocol for ipso-hydroxylation of aryl/heteroarylboronic acids.
- Saikia, Eramoni,Bora, Sankar Jyoti,Chetia, Bolin
-
p. 102723 - 102726
(2015/12/11)
-
- Preparation of phenolic compounds through catalyst-free ipso-hydroxylation of arylboronic acids
-
A novel method for the preparation of phenolic compounds through ipso-hydroxylation of the corresponding widely available arylboronic acid precursors is described. Through application of a novel PEG400-H 2O2 reactant system, a variety of substituted phenols and other aromatic analogues have been prepared in excellent yields at room temperature in the absence of any catalyst.
- Gohain, Mukut,Du Plessis, Maretha,Van Tonder, Johannes H.,Bezuidenhoudt, Barend C.B.
-
p. 2082 - 2084
(2014/04/03)
-
- Boric acid as highly efficient catalyst for the synthesis of phenols from arylboronic acids
-
A simple, efficient, and environmentally benign boric acid catalyzed methodology for the ipso-hydroxylation of arylboronic acid to phenol has been developed using aqueous hydrogen peroxide as an oxidizing agent and ethanol as the solvent. The versatility of this protocol is that the reactions were performed at room temperature in short reaction time under metal-, ligand-, and base-free conditions.
- Gogoi, Kongkona,Dewan, Anindita,Gogoi, Ankur,Borah, Geetika,Bora, Utpal
-
p. 127 - 130
(2014/04/03)
-
- Rapid and green synthesis of phenols catalyzed by a deep eutectic mixture based on fluorinated alcohol in water
-
A new deep eutectic mixture based on choline chloride and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was prepared and was found to be effective for the rapid transformation of aryl/heteroaryl boronic acids to the corresponding phenols in water using hydrogen peroxide as the oxidant. Broad substrate compatibility, metal- and additive-free conditions as well as reusability of the catalyst made this procedure more environmentally benign.
- Wang, Liang,Dai, Dong-Yan,Chen, Qun,He, Ming-Yang
-
-
- A mild and efficient protocol for the ipso-hydroxylation of arylboronic acids
-
An ipso-hydroxylation of arylboronic acids to phenols using aqueous H 2O2 as oxidant and acidic alumina as catalyst has been reported in this study. The reusability of the catalyst is also investigated.
- Gogoi, Ankur,Bora, Utpal
-
p. 1821 - 1823
(2013/04/24)
-
- Catalysis by Amberlite IR-120 resin: A rapid and green method for the synthesis of phenols from arylboronic acids under metal, ligand, and base-free conditions
-
A clean process has been developed for the ipso-hydroxylation of aryl and heteroaryl boronic acids to the corresponding phenols using commercially available and recyclable Amberlite IR-120 resin and aqueous hydrogen peroxide as an oxidizing agent. The ion-exchange sulfonic acid resin catalyst could be readily recycled by filtration and directly reused at least four times without any significant loss of activity.
- Mulakayala, Naveen,Ismail,Kumar, Kottur Mohan,Rapolu, Rajesh Kumar,Kandagatla, Bhaskar,Rao, Pallavi,Oruganti, Srinivas,Pal, Manojit
-
supporting information
p. 6004 - 6007,4
(2020/07/31)
-
- An iodine-promoted, mild and efficient method for the synthesis of phenols from arylboronic acids
-
A mild and efficient methodology for the ipso-hydroxylation of arylboronic acids to phenols has been developed using aqueous hydrogen peroxide as oxidizing agent and molecular iodine as catalyst. The reactions were performed at room temperature in short reaction time under metal-, ligand- and base-free conditions. Georg Thieme Verlag Stuttgart · New York.
- Gogoi, Ankur,Bora, Utpal
-
experimental part
p. 1079 - 1081
(2012/06/01)
-
- Simple and efficient CuI/PEG-400 system for hydroxylation of aryl halides with potassium hydroxide
-
This work reports a simple and efficient CuI/PEG-400 system for hydroxylation of aryl halides with potassium hydroxide. This protocol offers a direct transformation of aryl iodides or bromides to substituted phenols in great diversity. A very wide variety of functional groups are tolerated on aryl halides partners such as carboxyl, aldehyde and hydroxyl group.
- Chen, Junmin,Yuan, Tangjun,Hao, Wenyan,Cai, Mingzhong
-
experimental part
p. 1463 - 1465
(2012/06/18)
-
- Substituted oxoazaheterocyclyl compounds
-
This invention is directed to oxoazaheterocycyl compounds which inhibit Factor Xa, to oxoazaheterocycyl compounds which inhibit both Factor Xa and Factor IIa, to pharmaceutical compositions comprising these compounds, to intermediates useful for preparing these compounds, to a method of directly inhibiting Factor Xa and to a method of simultaneously directly inhibiting Factor Xa and Factor IIa..
- -
-
Page/Page column 75
(2008/06/13)
-
- A Clean One-step Synthesis of 2-Hydroxythiophene[Thiophen-2(5H)-one] by a Fenton-like [Copper(II)-Hydrogen Peroxide] Oxidation of Thiophene under Aqueous Conditions
-
Treatment of thiophene, suspended in an aqueous acidified solution of copper(II) sulfate, with hydrogen peroxide at room temperature results in a clean conversion into 2-hydroxythiophen in 59% yield, providing a simple route to this system; the use of other Fenton-like reagents also results in formation of 2-hydroxythiophene, but overall yields are lower.
- Allen, David W.,Clench, Malcolm R.,Hewson, Alan T.,Sokmen, Munevver
-
p. 242 - 243
(2007/10/03)
-
- Tautomerism of the Monohydroxy Derivatives of Five-Membered O, N, and S Heterocycles
-
The O-deuterated enolic tautomers 3-deuteroxybenzofuran, 3-deuteroxybenzothiophene, 3-deuteroxyindole, 3-deuteroxy-1-methylindole, 3-deuteroxyfuran, 3-deuteroxythiophene, 2-deuteroxybenzothiophene, and 2-deuteroxythiophene have been generated in solution in mixtures of CD3COCD3, CD3CN, or CD3SOCD3 with D2O by hydrolysis of their trimethylsilyl derivatives in the presence of DCl (1E-3 - 1E-4 M) and characterized by 1H NMR spectroscopy.Solutions of 3-hydroxypyrrole and of 3-hydroxy-1-methylpyrrole were obtained by methanolysis of their trimethylsilyl derivatives,evaporation of the methanol, and immediate dissolution in DMSO-d6.The carbocyclic analogues of the bicyclic heterocyclic enols 3-deuteroxyindene and 2-deuteroxyindene were also generated in solution.Attempts to prepare solutions of 2-deuteroxyfuran, 2-deuteroxypyrrole, and 2-deuteroxy-1-methylpyrrole were unsuccessful.The kinetics of ketonization of the OH forms of these enols have been investigated in water or aqueous acetonitrile solution.The equilibrium constants for the keto-enol tautomerism were also determined either by direct measurement when sufficient enol was present at equilibrium or as the ratio of the rate constant for enolization of the keto form to that for ketonization of the enol form, the former being determined by the iodine-trapping technique.The effect of solvent on the equilibrium constants was also studied.Sufficient data were available for the equilibrium between 3-hydroxyindole and 3-ketoindole for them to be analyzed by the four-parameter equation of Mills and Beak to yield an a value of 2.4 and a b value of -3.0.The pKas of the bicyclic enols were measured. 3-Hydroxybenzofuran and3-hydroxybenzothiophene are stronger acids than 3-hydroxyindole and 3-hydroxy-1-methylindole.The ketonization reactions are general acid and general base catalyzed and their mechanisms are discussed.
- Capon, Brian,Kwok, Fu-Chiu
-
p. 5346 - 5356
(2007/10/02)
-