- Silver-mediated fluorination of potassium aryltrifluoroborates with Selectfluor Dedicated to Professor Andrea Vasella on the occasion of his 71st birthday
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A simple and practical procedure for the silver-mediated fluorination of aryl- and heteroaryltrifluoroborates with electrophilic fluorine from Selectfluor and LiOH·H2O is presented. The reaction procedure is simple and easy to set up, the process produces fluorinated arenes and heteroarenes in good to excellent yields and a wide range of electronically and structurally diverse substrates are tolerated.
- Dubbaka, Srinivas Reddy,Narreddula, Venkateswara Reddy,Gadde, Satyanarayana,Mathew, Thresen
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p. 9676 - 9681
(2015/01/08)
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- Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
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Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
- Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
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p. 402 - 415
(2007/10/03)
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- Process for the preparation of fluoro compounds from the corresponding amines
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Compounds containing a primary amino group are converted into compounds containing a fluorine atom in place of the amino group by reaction of the amino compound with hydrogen fluoride and a nitrosating reagent under the influence of ultrasound or microwaves.
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- Preparation process of fluorine substituted aromatic compound
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A preparation process of a fluorine substituted aromatic compound comprising reacting an alkali metal or alkali earth metal salt of an aromatic compound having a hydroxy group with an organic fluorinating agent is disclosed. As a representative fluorinating agent, a bis-dialkylamino-difluoromethane compound, for example, 2,2′-difluoro-1,3-dimethylimidazolidine, is exemplified. According to the process, an industrially useful fluorinated aromatic compound, for example, a fluorobenzene, a fluorine substituted benzophenone, a fluorine substituted diarylsulfone can be prepared with ease in economy without specific equipment.
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- Process for preparing o-alkylfluorobenzenes
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o-Alkylfluorobenzenes are advantageously prepared by heating the corresponding chloroformates to from 70° to 200° C. in the liquid phase in the presence of hydrogen fluoride and in the presence of an inert diluent other than a halogenated alkane.
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- Liquid-Phase Decarboxylation of Aromatic Haloformates: A New Access to Chloro- and Fluoroaromatics
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The treatment of phenyl chloroformates 1 with a Lewis acid in the liquid phase resulted in decarboxylation to the corresponding chloroaromatics 2. Fluoroaromatic compounds were synthesized from phenylchloroformates 1 through a sequential fluorination/decarboxylation in the liquid phase by treatment with excess anhydrous hydrogen fluoride under mild conditions. In all cases, yields were increased by performing the reaction in 1,2,4-trichlorobenzene, which is inert to Friedel-Crafts reactions.
- Lui, Norbert,Marhold, Albrecht,Rock, Michael H.
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p. 2493 - 2496
(2007/10/03)
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- Dehalogenation of organic halides by flash vacuum pyrolysis over magnesium: A versatile synthetic method
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Flash vacuum pyrolysis over magnesium at 600°C results in efficient dehalogenation of a variety of organic halides and provides a preparatively useful method for C-C bond formation and other reactions.
- Aitken, R. Alan,Hodgson, Philip K. G.,Oyewale, Adebayo O.,Morrison, John J.
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p. 1163 - 1164
(2007/10/03)
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- Aryl fluoride syntheses involving reactions of aryllead triacetates with boron trifluoride-diethyl ether complex
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Aryllead(IV) triacetates react at room temperature with BF3.Et2O to give the corresponding aryl fluoride in moderate to good yields; triarylboroxines, electron rich aryltrimethylsilanes and some arenes, which yield aryllead triacetates in acid catalysed reactions with lead tetraacetate, are converted directly into aryl fluorides when stirred with lead tetraacetate in BF3.Et2O. An investigation of the mechanism of the fluoro-deplumbation reaction indicates that it probably proceeds by acid catalysed heterolytic cleavage of the C-Pb bond to produce an aryl cation.
- De Meio,Morgan,Pinhey
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p. 8129 - 8138
(2007/10/02)
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- Facile conversion of arenediazonium salts to the corresponding fluoroarenes using boron trifluoride diethyl ether complex
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The conversion of various arenediazonium salts 1 to the corresponding fluoroarenes 2 has been achieved in good yields under mild conditions in boron trifluoride diethyl ether complex.
- Shinhama,Aki,Furuta,Minamikawa
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p. 1577 - 1582
(2007/10/02)
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