1003-09-4Relevant articles and documents
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Barker et al.
, p. 615 (1972)
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Cu3(BTC)2 as heterogeneous catalyst for the room temperature oxidative hydroxylation of arylboronic acids
Dhakshinamoorthy, Amarajothi,Asiri, Abdullah M.,Garcia, Hermenegildo
, p. 2895 - 2899 (2016)
A well known copper based-metal organic framework (MOF), namely Cu3(BTC)2, is a suitable heterogeneous catalyst to promote the oxidative room-temperature hydroxylation of arylboronic acids to the corresponding phenols by H2O2. Using 0.5 equiv of H2O2, Cu3(BTC)2 exhibits 80% conversion in 60 min that is higher than 70% conversion achieved with Fe(BTC) under the same conditions and reaction time. Cu3(BTC)2 is reusable with no significant drop in the activity. Furthermore, powder XRD of the reused Cu3(BTC)2 shows no changes in crystallinity compared to the fresh Cu3(BTC)2, indicating catalyst stability is maintained under reaction conditions. The scope of Cu3(BTC)2 as heterogeneous catalyst for the oxidative hydroxylation was studied for various phenylboronic acids.
CATALYTIC REDUCTIVE DEHALOGENATION OF THIOPHENE DERIVATIVES
Sharf, V. Z.,Taits, S. Z.,Gurovets, A. S.,Vol'kenshtein, Yu. B.,Fabrichnyi, B. P.,Shcherbakova, S. I.
, p. 130 - 133 (1982)
A method for the preparation of 3-substituted derivatives of thiophene by reductive dehalogenation of 2,5-dihalo-substituted thiophenes in the presence of a palladium complex is proposed.The dehalogenation reaction is a stepwise process.The presence of an acyl group in the 3 position increases the rate of the process.
Halogenations of Aromatic Compounds with Halide Anions in the Presence of Nitrobenzenesulfonyl Peroxides. A Novel Method for the Formation of Positive Halogens
Yoshida, Masato,Mochizuki, Hideki,Kamigata, Nobumasa
, p. 2017 - 2020 (1988)
A novel type of positive halogens, sulfonyl hypochlorite or sulfonyl hypobromite was formed in the reactions of halide anions with nitrobenzenesulfonyl peroxides; these hypohalites could be used as effective reagents for halogenation of aromatic rings.
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Berman,Price
, p. 5474 (1957)
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Vaitiekunas,Nord
, p. 1764,1767 (1953)
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Green halogenation of aromatic heterocycles using ammonium halide and hydrogen peroxide in acetic acid solvent
D'Aleo, Danielle N.,Allard, Sheena R.,Foglia, Cassandra C.,Parent, Shawna L.M.,Rohr, David J.,Gottardo, Christine,MacKinnon, Craig D.
, p. 679 - 683 (2013)
The green generation of X+ (X = Br, I) using hydrogen peroxide in aqueous acetic acid allows access to aromatic heterocyclic halides in yields and purities comparable to syntheses employing N-bromosuccinimide. In activated and unsubstituted thiophene rings, regioselectivity is quantitative for positions α to the sulfur; pyrroles also give quantitative reactions, at least initially. Deactivated rings, including furans and thiazoles, as well as thiophenes with strongly electron-withdrawing groups showed little to no reactivity under the conditions investigated. The reaction shows remarkable functional group tolerance (to alcohol, nitro, alkyl, halo, and carbonyl groups), as shown through reaction with substituted phenols. In all bromination reactions, reaction yields and regiochemistry were very similar to reactions involving N-bromosuccinimide in tetrahydrofuran solvent.
Biphasic Electrophilic Halogenation of Activated Aromatics and Heteroaromatics with N-Halosuccinimides Catalyzed by Perchloric Acid
Goldberg, Yuri,Alper, Howard
, p. 3072 - 3075 (1993)
Catalytic amounts of 70percent perchloric acid (0.1 - 10, mostly 0.1 - 1, mol percent, based on substrate) initiate the regioselective halogenation of activated aromatics and heteroaromatics with N-halosuccinimide (NXS, X = Cl or Br) in two-phase solid-liquid systems (NXS/hexane or NXS/CCl4) at room temperature to give ring-halogenated products in high yields.For example, thiophene is transformed to 2-halo or 2,5-dihalo derivatives (yield 82-98percent) using 1 or 2 equiv of NXS, respectively.Unsymmetrical 2,5-dihalothiophenes are obtained in 70-82percent yield by reacting 2-halothiophenes with an appropriate NXS.The reaction of 3-bromothiophene with NBS affords 2,3-dibromothiophene in 93-99percent yield. 1,3-Dimethoxybenzene and 2,3-dimethylanisole are halogenated regiospecifically at the 4-position to give the corresponding products in 81-94percent yield.
Influence of solvent polarity and viscosity on nonradiative processes in oligothiophenes with intramolecular charge transfer
Bondarev, S. L.,Knvukshto, V. N.,Tikhomirov, S. A.,Kalosha, I. I.,Bobrov, S. A.,Masalov, N. V.,Nevar, N. M.,Tyvorskii, N. M.,Kel'in, A. V.,Kulinkovich, O. G.,Dzilinski, K.
, p. 230 - 237 (2002)
By the methods of luminescence, picosecond spectroscopy, and quantum-chemical calculations the mechanisms of electron excitation energy deactivation in some oligothiophenes with intramolecular charge transfer depending on the solvent polarity and viscosity have been investigated. While for 2-N-piperidino-5-(2',2'-dicyanovinyl)thiophene (PDCVT) the main channel of nonradiative deactivation is the transition to a lower intermediate state with a "twisted" double bond controlled by the medium viscosity, in the case of (E)-{2-[2-5-piperidino-2-thienyl]-6-(triftuoridemethyl)-4H-4-pyranylidene}propanedinitryl (PTFDN) fluorescence quenching is initiated by the solvent polarity. For two other oligothiophenes, 2-N-piperidino-5-cyanothiophene (PCT) and 2-N-piperidino-5"-cyanoterthiophene (PCTT), differing in the length of the thiophene chain, we have revealed, along with the effective quenching of fluorescence in short-chain PCT (independent of the solvent polarity and viscosity), an increase in the radiation capacity in PCTT with increasing polarity of the solvent. The possible mechanisms of nonradiative deactivation in the investigated oligothiophenes are discussed.
Regioselective photochemical and microwave mediated monobromination of aromatic compounds using 2,4,4,6-tetrabromo-2,5-cyclohexadienone
Gupta, Neeraj,Kad, Goverdhan L.,Singh, Vasundhara,Singh, Jasvinder
, p. 3421 - 3428 (2007)
Bromination of different aromatic substrates have been described using 2,4,4,6-tetrabromo-2,5-cyclohexadienone in conjunction with microwave and ultraviolet radiations. Important features of the work include high regioselectivity obtained in very short to moderate reaction time, atom economy, and recyclability of the reagent. Copyright Taylor & Francis Group, LLC.
N-bromosuccinimide - Chloroform, a more convenient method to nuclear brombsate reactive aromatic hydrocarbons
Mitchell, Reginald H.,Chen, Yongsheng,Zhang, Ji
, p. 715 - 719 (1997)
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Nucleophilic C-H Etherification of Heteroarenes Enabled by Base-Catalyzed Halogen Transfer
Bandar, Jeffrey S.,Klaus, Danielle R.,Puleo, Thomas R.
supporting information, p. 12480 - 12486 (2021/08/24)
We report a general protocol for the direct C-H etherification of N-heteroarenes. Potassium tert-butoxide catalyzes halogen transfer from 2-halothiophenes to N-heteroarenes to form N-heteroaryl halide intermediates that undergo tandem base-promoted alcohol substitution. Thus, the simple inclusion of inexpensive 2-halothiophenes enables regioselective oxidative coupling of alcohols with 1,3-azoles, pyridines, diazines, and polyazines under basic reaction conditions.
Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations
Deckers, Kristina,Fricke, Christoph,Schoenebeck, Franziska
supporting information, p. 18717 - 18722 (2020/08/25)
While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive-free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.
BIARYL PHENOXY GROUP IV TRANSITION METAL CATALYSTS FOR OLEFIN POLYMERIZATION
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, (2020/05/14)
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:
