- Photochemical Sandmeyer-type Halogenation of Arenediazonium Salts
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Trihalide salts were found to efficiently promote photochemical dediazotizing halogenations of diazonium salts. In contrast to classical Sandmeyer reactions, no metal catalysts are required to achieve high yields and outstanding selectivities for halogena
- Belitz, Florian,Goo?en, Lukas J.,Manu Martínez, ángel,Schmid, Rochus,Sivendran, Nardana,Sowa Prendes, Daniel
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supporting information
(2022/01/19)
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- Site-Specific Alkene Hydromethylation via Protonolysis of Titanacyclobutanes
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Methyl groups are ubiquitous in biologically active molecules. Thus, new tactics to introduce this alkyl fragment into polyfunctional structures are of significant interest. With this goal in mind, a direct method for the Markovnikov hydromethylation of alkenes is reported. This method exploits the degenerate metathesis reaction between the titanium methylidene unveiled from Cp2Ti(μ-Cl)(μ-CH2)AlMe2 (Tebbe's reagent) and unactivated alkenes. Protonolysis of the resulting titanacyclobutanes in situ effects hydromethylation in a chemo-, regio-, and site-selective manner. The broad utility of this method is demonstrated across a series of mono- and di-substituted alkenes containing pendant alcohols, ethers, amides, carbamates, and basic amines.
- Bartfield, Noah M.,Frederich, James H.,Law, James A.
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supporting information
p. 14360 - 14364
(2021/05/27)
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- Visible-Light-Photosensitized Aryl and Alkyl Decarboxylative Functionalization Reactions
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Despite significant progress in aliphatic decarboxylation, an efficient and general protocol for radical aromatic decarboxylation has lagged far behind. Herein, we describe a general strategy for rapid access to both aryl and alkyl radicals by photosensitized decarboxylation of the corresponding carboxylic acids esters followed by their successive use in divergent carbon–heteroatom and carbon–carbon bond-forming reactions. Identification of a suitable activator for carboxylic acids is the key to bypass a competing single-electron-transfer mechanism and “switch on” an energy-transfer-mediated homolysis of unsymmetrical σ-bonds for a concerted fragmentation/decarboxylation process.
- Patra, Tuhin,Mukherjee, Satobhisha,Ma, Jiajia,Strieth-Kalthoff, Felix,Glorius, Frank
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p. 10514 - 10520
(2019/07/12)
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- A general electrochemical strategy for the Sandmeyer reaction
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Herein we report a general electrochemical strategy for the Sandmeyer reaction. Using electricity as the driving force, this protocol employs a simple and inexpensive halogen source, such as NBS, CBrCl3, CH2I2, CCl4, LiCl and NaBr for the halogenation of aryl diazonium salts. In addition, we found that these electrochemical reactions could be performed using anilines as the starting material in a one-pot fashion. Furthermore, the practicality of this process was demonstrated in the multigram scale synthesis of aryl halides using highly inexpensive graphite as the electrode. A series of detailed mechanism studies have been performed, including radical clock and radical scavenger study, cyclic voltammetry analysis and in situ electron paramagnetic resonance (EPR) analysis.
- Liu, Qianyi,Sun, Beiqi,Liu, Zheng,Kao, Yi,Dong, Bo-Wei,Jiang, Shang-Da,Li, Feng,Liu, Guoquan,Yang, Yang,Mo, Fanyang
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p. 8731 - 8737
(2018/12/10)
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- Regioselective Halogenation of Arenes and Heterocycles in Hexafluoroisopropanol
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Regioselective halogenation of arenes and heterocycles with N-halosuccinimides in fluorinated alcohols is disclosed. Under mild condition reactions, a wide diversity of halogenated arenes are obtained in good yields with high regioselectivity. Additionally, the versatility of the method is demonstrated by the development of one-pot sequential halogenation and halogenation-Suzuki cross-coupling reactions.
- Tang, Ren-Jin,Milcent, Thierry,Crousse, Benoit
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p. 930 - 938
(2018/01/28)
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- Synthesis and catalytic reactivity of mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes
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The reactions of five dinuclear carbonyl complexes [(η 5-C5Me4R)Mo(CO)3]2 [R = allyl, n Bu, t Bu, Ph, Bz] with I2 in chloroform solution gave the corresponding mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes [(η 5-C5Me4R)MoI(CO)3] [R = allyl (1), n Bu (2), t Bu (3), Ph (4), Bz (5)]. The molecular structures of complexes 2, 3 and 5 were determined by X-ray diffraction analysis. The results show that the substituent in the ring can directly affect the Mo-I bond distances; the more sterically hindered the substituent, the longer the Mo-I bond. Friedel-Crafts reactions of aromatic compounds with a variety of alkylation reagents catalyzed by the complexes showed that all of these mononuclear molybdenum carbonyl complexes have catalytic activity in Friedel-Crafts alkylation reactions. Indeed, compared with traditional catalysts, these mononuclear metal carbonyl complexes have obvious advantages such as higher activities, mild reaction conditions, high selectivity, simple post-processing, and environmentally friendly chemistry.
- Ma, Zhi-Hong,Lv, Lin-Qian,Wang, Hong,Han, Zhan-Gang,Zheng, Xue-Zhong,Lin, Jin
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p. 225 - 233
(2016/02/20)
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- ANTIOXIDANTS AND METHODS TO MAXIMIZE PERFORMANCE
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A method of preventing or reducing the level of degradation of an organic substrate is described, wherein a composition is formed that includes the organic substrate together with an effective amount of a sacrificial base and a diarylamine antioxidant.
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Page/Page column 29
(2016/09/22)
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- On the ionizing properties of supercritical carbon dioxide: Uncatalyzed electrophilic bromination of aromatics
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Supercritical carbon dioxide (scCO2), a solvent with a zero dipole moment, low dielectric constant, and no hydrogen bonding behavior, is a suitable medium to perform the uncatalyzed electrophilic bromination of weakly activated aromatics with no interference of radical pathways. The ability of scCO2 to promote these reactions matches those of strongly ionizing solvents such as aqueous acetic and trifluoroacetic acids. Conversely, carbon tetrachloride, with similar polarity parameters to scCO2, leads exclusively to side chain functionalization. The strong quadrupole moment, and the acidic, but non basic, Lewis character of carbon dioxide, are proposed as key factors for the singular performance of scCO2 in reactions involving highly polar and ionic intermediates.
- Delgado-Abad, Thais,Martnez-Ferrer, Jaime,Reig-Lpez, Javier,Mello, Rossella,Acerete, Rafael,Asensio, Gregorio,Gonzlez-Nez, Mara Elena
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p. 51016 - 51021
(2015/01/16)
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- Direct bromination of hydrocarbons catalyzed by Li2MnO 3 under oxygen and photo-irradiation conditions
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A method for the direct bromination of hydrocarbons with Br2 using a ubiquitous and inexpensive catalyst is highly desirable. Herein, we report the selective mono-bromination of hydrocarbons in good yield using Li2MnO3 as a catalyst under irradiation with a fluorescent room light. This new catalyst can be recycled. The effect of light was investigated using action spectra, which revealed that the reaction occurred on the surface of the catalyst.
- Nishina, Yuta,Morita, Junya,Ohtani, Bunsho
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p. 2158 - 2162
(2013/03/13)
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- Halodeboronation of organotrifluoroborates using tetrabutylammonium tribromide or cesium triiodide
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Halodeboronation of organotrifluoroborates using commercially available tetrabutylammonium tribromide (TBATB) or cesium triiodide in aqueous medium is reported. The mild, transition metal-free method has proven to be tolerant of a wide range of functional groups. High regio- and chemoselectivity are observed. Two synthetic routes to (Z)-dibromoalkenes from alkynes, through stereodefined (Z)-2-bromoalkenyltrifluoroborates and (Z)-1,2-bis(boryl) alkenyltrifluoroborates, have been developed using the TBATB mediated bromodeboronation as the key step.
- Yao, Min-Liang,Kabalka, George W.,Blevins, David W.,Reddy, Marepally Srinivasa,Yong, Li
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experimental part
p. 3738 - 3743
(2012/06/30)
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- Synthesis of an extremely sterically shielding N-heterocyclic carbene ligand
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The N-heterocyclic carbene (NHC) ligand IPr** features substituents of unprecedented steric demand (IPr** = 1,3-bis[2,6-bis[(4-tert-butylphenyl)methyl]-4-methylphenyl]imidazol-2-ylidene). The NHC structure is an advanced derivative of the IPr system, and of the IPr* by Berthon-Gelloz and Marko. In the IPr** ancillary ligand, two para-methyl are introduced and eight methyl groups of IPr are formally replaced by a 4-tert-butylphenyl substituent, respectively, thereby sterically shielding both a coordinated metal and its second ligand. Favorable features of ligand and late transition metal complexes include high solubility, aesthetic NMR spectra, and a tendency towards crystallization. ARKAT-USA, Inc.
- Weber, Simone G.,Loos, Christian,Rominger, Frank,Straub, Bernd F.
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p. 226 - 242
(2013/09/24)
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- Ruthenium-catalyzed transformation of aryl and alkenyl triflates to halides
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Aryl triflates were transformed to aryl bromides/iodides simply by treating them with LiBr/NaI and [Cp*Ru(MeCN)3]OTf. The ruthenium complex also catalyzed the transformation of alkenyl sulfonates and phosphates to alkenyl halides under mild conditions. Aryl and alkenyl triflates undergo oxidative addition to a ruthenium(II) complex to form η'1- arylruthenium and 1-ruthenacyclopropene intermediates, respectively, which are transformed to the corresponding halides.
- Imazaki, Yusuke,Shirakawa, Eiji,Ueno, Ryota,Hayashi, Tamio
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supporting information
p. 14760 - 14763
(2012/11/07)
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- Ultrasound assisted Friedel-Crafts acylation of aromatics using ferric sulphate as catalyst
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The use of ultrasound in the acylation reactions of various aromatics and polyaromatics with different acyl chlorides, in the presence of catalytic amount of ferric sulphate at room temperature, gives good yields of the respective ketones with a short reaction time. A facile and simple synthesis of various aromatic ketones using Friedel-Crafts acylation has been established from the corresponding acid chlorides and aromatic or polyaromatic compounds, respectively under mild reaction conditions with shorter reaction times (30-45 min) and in reasonable yields. This method offers the advantage of low cost and ease of purification of the products because of the small amount of ferric sulphate used in these reactions.
- Sridharan, Anandhi,Gopalakrishnan, Geetha
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experimental part
p. 1192 - 1195
(2011/10/18)
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- Chemoselective bromodeboronation of organotrifluoroborates using tetrabutylammonium tribromide: Application in (Z)-dibromoalkene syntheses
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(Chemical Equation Presented) Tetrabutylammonlum trlbromlde (TBATB) has been found to be a unique bromodeboronatlon reagent for organotrlf luoroborates. When compared to previously reported bromodeboronatlon methods, the mild and metal-free reaction conditions tolerate a wider range of functional groups. High reglo- and chemoselectlvlty are observed In the presence of both unsaturated carbon-carbon bonds and aldehyde functional groups. An efficient synthetic route to (Z)-dlbromoalkenes from terminal alkynes has been developed using the TBATB-medlated bromodeboronatlon as a key step.
- Yao, Min-Liang,Reddy, Marepally Srinivasa,Li, Yong,Walfish, Ingrid,Blevins, David W.,Kabalka, George W.
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supporting information; experimental part
p. 700 - 703
(2010/04/02)
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- Thallium(III) oxide as an oxidative reagent in organic chemistry
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Oxidative properties of thallium(III) oxide in various organic reactions were studied. Oxidative bromination of organic compounds in Tl2O 3-KBr-trifluoroacetic acid system was carried out. New synthetic method for preparation of diphenylthallium salts from phenylhydrazine and thallium(III) oxide was developed.
- Gun'kin
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scheme or table
p. 451 - 454
(2010/08/04)
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- Non-catalytic conversion of C-F bonds of benzotrifluorides to C-C bonds using organoaluminium reagents
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A facile method for the conversion of C-F bonds of benzotrifluorides to C-C bonds has been developed using aluminium reagents in the absence of catalysts.
- Terao, Jun,Nakamura, Misaki,Kambe, Nobuaki
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supporting information; experimental part
p. 6011 - 6013
(2010/11/16)
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- Halo- and azidodediazoniation of arenediazonium tetrafluoroborates with trimethylsilyl halides and trimethylsilyl azide and Sandmeyer-type bromodediazoniation with Cu(I)Br in [BMIM][PF6] ionic liquid
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(Chemical Equation Presented) Reaction of [ArN2][BF4] salts immobilized in [BMIM][PF6] ionic liquid (IL) with TMSX (X = I, Br) and TMSN3 represents an efficient method for the preparation of iodo-, bromo-, and azido-derivatives via dediazoniation. The reactions can also be effected starting with ArNH2 by in situ diazotization with [NO][BF4] followed by reaction with TMSX or TMSN3. Depending on the substituents on the benzenediazonium cation, competing fluorodediazoniation (ArF formation) and hydrodediazoniation (ArH formation) were observed. Dediazoniation with TMSN3 and with TMSI generally gave the highest chemoselectivity toward ArN3 and ArI formation. The IL was recycled and reused up to 5 times with no appreciable decrease in the conversions. Multinuclear NMR monitoring of the interaction of [ArN 2][BF4]/TMSX, [BMIM][PF6]/TMSX, and [BMIM][PF6]/TMSX/[ArN2][BF4] indicated that TMSF is formed primarily via [ArN2][BF4]/ TMSX, generating [ArN2][X] in situ, which gives ArX on dediazoniation. Competing formation of ArF in Sandmeyer-type bromodediazoniation of [ArN 2][BF4] with Cu(I)Br immobilized in the IL points to significant involvement of heterolytic dediazoniation.
- Hubbard, Abigail,Okazaki, Takao,Laali, Kenneth K.
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p. 316 - 319
(2008/09/17)
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- The conversion of phenols to the corresponding aryl halides under mild conditions
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Mild, novel procedures have been developed for the syntheses of aryl halides from the corresponding phenols in modest to good yields via boronate ester intermediates.
- Thompson, Alicia L. S.,Kabalka, George W.,Akula, Murthy R.,Huffman, John W.
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p. 547 - 550
(2007/10/03)
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- Thrombopoietin mimetics
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Invented are non-peptide TPO mimetics. Also invented is a method of treating thrombocytopenia, in a mammal, including a human, in need thereof which comprises administering to such mammal an effective amount of a selected substituted naphthimidazole derivative.
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- Synthesis of t-butylated diphenylanthracene derivatives as blue host materials for OLED applications
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This paper describes the cost-effective synthesis and the photoluminescence of diphenylanthracene derivatives, which are found to be potential blue host materials for organic light emitting diode (OLED) technology.
- Balaganesan, Banumathy,Shen, Wen-Jian,Chen, Chin H.
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p. 5747 - 5750
(2007/10/03)
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- Aromatic allylation via diazotization: Metal-free C-C bond formation
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A new method for the synthesis of allyl aromatic compounds not involving any metal-containing reagent or catalyst has been developed. Arylamines substituted with a large number of different substituents were converted via diazotizative deamination with tert-butyl nitrite in allyl bromide and acetonitrile to the corresponding allyl aromatic compounds. The allylation reaction was found to be suitable for larger scale synthesis due to short reaction times, a nonextractive workup, and robustness toward moisture, air, and type of solvent.
- Ek, Fredrik,Axelsson, Oskar,Wistrand, Lars-Goeran,Frejd, Torbjoern
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p. 6376 - 6381
(2007/10/03)
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- Highly efficient and selective electrophilic and free radical catalytic bromination reactions of simple aromatic compounds in the presence of reusable zeolites
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Reactions of mono-substituted aromatics of moderate activity with bromine in the presence of stoichiometric amounts of zeolite NaY proceed in high yield and with high selectivity to the corresponding para-bromo products. The zeolites can easily be regenerated by heating and reused. Similar para-selectivity can be achieved in the case of toluene by use of tert-butyl hypobromite as reagent, zeolite HX as catalyst, and a solvent comprising a mixture of tetrachloromethane and diethyl ether. Radical bromination of ethyl 4-methylbenzoate using bromine in the presence of light is catalysed by various zeolites and affords a high yield of ethyl 4-(bromomethyl)benzoate but with no great improvement in selectivity for monobromination.
- Smith, Keith,El-Hiti, Gamal A.,Hammond, Mark E.W.,Bahzad, Dawoud,Li, Zhaoqiang,Siquet, Christophe
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p. 2745 - 2752
(2007/10/03)
-
- The use of supported zinc bromide for the fast and selective bromination of aromatic substrates
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Zinc bromide supported on acid activated montmorillonite (K-10) or mesoporous silica (100 A) is a fast, selective catalyst for the para-bromination of activated and mildly deactivated aromatic substrates. The optimum loading of zinc bromide on K-10 is 1.25 mmol/g and 1.75 mmol/g on the higher surface area silica (100 A). Thermal activation of these catalysts at 200 °C results in optimum activity and selectivity. Also, system optimisation has allowed harmful chlorinated solvents to be replaced by less damaging hydrocarbon solvents.
- Ross, Joanne C.,Clark, James H.,Macquarrie, Duncan J.,Barlow, Simon J.,Bastock, Tony W.
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p. 245 - 249
(2013/09/08)
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- Environmentally friendly catalysis using supported reagents: The fast and selective bromination of aromatic substrates using supported zinc bromide
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Zinc bromide supported on mesoporous silica or acid-activated montmorillonite is a fast, efficient, selective and reusable catalyst for the para-bromination of activated and moderately deactivated aromatic substrates.
- Clark, James H.,Ross, Joanne C.,Macquarrie, Duncan J.,Barlow, Simon J.,Bastock, Tony W.
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p. 1203 - 1204
(2007/10/03)
-
- Facile synthesis of pivalophenones by an ultrasound assisted iodine catalysed Friedel-Crafts acylation reaction
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The use of ultrasound in the acylation reactions of various aromatics and heterocyclics with pivaloyl chloride in the presence of catalytic amount of iodine, without any added solvent and at room temperature, gives excellent yields of the respective pivalophenones in a short reaction time.
- Gopalakrishnan, Geetha,Anandhi,Narasimhan
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p. 1197 - 1198
(2007/10/03)
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- A facile synthesis of pivalophenones by ultrasound assisted AlCl3 catalysed Friedel-Crafts reaction
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Pivalophenones have been prepared by the acylation reaction of various aromatic and heterocyclic compounds with pivaloyl chloride using AlCl3 as catalyst under sonochemical conditions in a short reaction time and in reasonable yields.
- Gopalakrishnan, Geetha,Anandhi,Narasimhan
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p. 1194 - 1196
(2007/10/03)
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- Pyridylphenyl nitrogen heterocycle-substituted carbinols and derivatives thereof with anti-inflammatory activity
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Pyridylphenyl nitrogen heterocycle-substituted carbinols and derivatives thereof and pharmaceutical compositions containing such compounds are useful for treating inflammatory diseases in mammals.
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- Halogenation Using Quaternary Ammonium Polyhalides. XIV. Aromatic Bromination and Iodination of Arenes by Use of Benzyltrimethylammonium Polyhalides-Zinc Chloride System
-
The reaction of arenes with benzyltrimethylammonium tribromide or benzyltrimethylammonium dichloroiodate in acetic acid in the presence of ZnCl2 at room temperature or at 70 deg C gave brome- or iodo-substituted arenes in good yield, respectively.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Moriwaki, Masayuki,Tanaka, Toshio,Fujisaki, Shizuo,Okamoto, Tsuyoshi
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p. 439 - 443
(2007/10/02)
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- BROMINATION OF AROMATIC MOLECULES WITH POLYMER SUPPORTED REAGENTS
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Crosslinked co poly/styrene-4-vinyl(N-hexylpyridinium bromide) was converted with bromine or chlorine to insoluble polymer supported complexes 1 or 2 respectively, and their reactivity studied in reactions with various aromatic molecules.Reagent 1 was found in all cases to be milder than reagent 2 and regiospecifically transformed alkoxy and amino substituted benzenes (3) into 4-bromo derivatives, while corresponding reactions with 2 resulted in dibromo derivatives.Several benzoheterocyclic molecules were converted with 1 to substitution or addition products, i.e. 2,3-dibromo-N-methylpyrrole, 3-bromobenzo/b/thiophene, and 2,3-dibromo-2,3-dihydrobenzofuran.In the series of ortho-alkyl disubstituted benzene derivatives, i.e. o-xylene, indane, and tetraline, where the Mills-Nixon effect was established with various electrophilic reagents, bromination reactions with 2 showed higher β-selectivity than the corresponding reactions with bromine.The rate of bromination in various alkyl substituted benzenes with reagent 2 depended on the magnitude of the alkyl group, as well as the para/ortho regioselectivity, amounting to 100percent in the case of tert-butylbenzene.
- Zajc, Barbara,Zupan, Marko
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p. 7869 - 7878
(2007/10/02)
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- Novel Aromatic Bromination Using BrF Prepared Directly from the Corresponding Elements
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BrF, made directly from the corresponding elements, may be used without any catalyst as an efficient electrophilic brominating agent in its reactions with activated and deactivated aromatic rings.
- Rozen, Shlomo,Brand, Michael
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p. 752 - 753
(2007/10/02)
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- Photochemical Bromination of Simple Arenes
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Photochemical bromination of benzene, fluorobenzene, chlorobenzene, t-butylbenzene, α,α,α-trifluorotoluene, and (in tetrachloromethane) biphenyl and naphthalene gives substitution products and adducts such as 1,2,3,4,5,6-hexabromocyclohexane (1).The decomposition of (1) and of the analogous chlorobenzene adduct (3) under photochemical conditions gives the parent arene, the monobrominated halogenobenzene, and bromine which may be scavenged by toluene to give benzyl bromide or by benzene to give bromobenzene and dibromobenzenes.Addition is a kinetically controlled process, so that the mechanism of formation of these aryl bromides must be largely through the reversible formation of these adducts.This is consistent with the unusual orientation of apparent attack by bromine upon the arene substrates, since the relative amounts of the isomeric aryl bromides is a consequence of the relative stabilities and ease of elimination of HBr and Br2 from a family of adducts. The range of isomer distribution found within the reaction of each arene with bromine is consistent with two competing processes involved in the formation of the aryl bromides; one of these might by the direct homolytic substitution by bromine atoms upon the arene.
- Bolton, Roger,Bhangar, Muhammad Iqbal,Williams, Gareth H.
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p. 893 - 896
(2007/10/02)
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