- Temperature Controls Guest Uptake and Release from Zn4L4 Tetrahedra
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We report the preparation of triazatruxene-faced tetrahedral cage 1, which exhibits two diastereomeric configurations (T1 and T2) that differ in the handedness of the ligand faces relative to that of the octahedrally coordinated metal centers. At lower temperatures, T1 is favored, whereas T2 predominates at higher temperatures. Host-guest studies show that T1 binds small aliphatic guests, whereas T2 binds larger aromatic molecules, with these changes in binding preference resulting from differences in cavity size and degree of enclosure. Thus, by a change in temperature the cage system can be triggered to eject one bound guest and take up another.
- Zhang, Dawei,Ronson, Tanya K.,Güryel, Songül,Thoburn, John D.,Wales, David J.,Nitschke, Jonathan R.
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supporting information
p. 14534 - 14538
(2019/10/11)
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- Synthesis of enantioenriched alkylfluorides by the fluorination of boronate complexes
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The enantiospecific conversion of chiral secondary boronic esters into alkylfluorides is reported. Boronate complexes derived from boronic esters and PhLi were used as nucleophiles, with Selectfluor II as the electrophilic fluorinating agent, to afford alkylfluorides in short reaction times. The addition of styrene as a radical trap was found to enhance enantiospecificity. A broad range of alkyl boronic esters were converted into alkylfluorides with almost complete enantiospecificity by this method.
- Sandford, Christopher,Rasappan, Ramesh,Aggarwal, Varinder K.
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supporting information
p. 10100 - 10103
(2015/09/01)
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- C-HALOGEN BOND FORMATION
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Methods of halogenating a carbon containing compound having an sp3 C-H bond are provided. Methods of fluorinating a carbon containing compound comprising halogenation with Cl or Br followed by nucleophilic substitution with F are provided. Methods of direct oxidative C-H fluorination of a carbon containing compound having an sp3 C-H bond are provided. The halogenated products of the methods are provided.
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Paragraph 0139-0140; 0142-0144; 0151; 0163-0164
(2013/03/26)
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- Oxidative aliphatic C-H fluorination with fluoride ion catalyzed by a manganese porphyrin
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Despite the growing importance of fluorinated organic compounds in drug development, there are no direct protocols for the fluorination of aliphatic C-H bonds using conveniently handled fluoride salts. We have discovered that a manganese porphyrin complex catalyzes alkyl fluorination by fluoride ion under mild conditions in conjunction with stoichiometric oxidation by iodosylbenzene. Simple alkanes, terpenoids, and even steroids were selectively fluorinated at otherwise inaccessible sites in 50 to 60% yield. Decalin was fluorinated predominantly at the C2 and C3 methylene positions. Bornyl acetate was converted to exo-5-fluoro-bornyl acetate, and 5a-androstan-17-one was fluorinated selectively in the A ring. Mechanistic analysis suggests that the regioselectivity for C-H bond cleavage is directed by an oxomanganese(V) catalytic intermediate followed by F delivery via an unusual manganese(IV) fluoride that has been isolated and structurally characterized.
- Liu, Wei,Huang, Xiongyi,Groves, John T.,Cheng, Mu-Jeng,Nielsen, Robert J.,Goddard III, William A.
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p. 1322 - 1325,4
(2020/08/31)
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- Fluorodecarboxylation, rearrangement and cyclisation: the influence of structure and environment on the reactions of carboxylic acids with xenon difluoride
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The reactions of structurally diverse carboxylic acids with XeF2 in both CH2Cl2/Pyrex and CH2Cl2/PTFE have been studied. Pyrex appears to be a very effective heterogeneous catalyst for an electrophilic mode of reaction of polarised XeF2, leading to rearrangement, cyclisation and cationic products. In CH2Cl2/PTFE, fluorodecarboxylation is the main mode of reaction, in accordance with previous studies, and may occur via a SET reaction of unpolarised XeF2.
- Ramsden, Christopher A.,Shaw, Maxine M.
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experimental part
p. 3321 - 3324
(2009/08/09)
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- Elementalfluorine. Part 14.1 Electrophilic fluorination and nitrogen functionalisation of hydrocarbons
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Selective fluorination of a range of hydrocarbons was achieved by reaction with either elemental fluorine or Selectfluor, an electrophilic fluorinating reagent of the N-F class. An electrophilic mechanism is envisaged. On prolonged reaction, the strongly acidic reaction medium that is formed upon substitution of hydrogen by fluorine when Selectfluor is used as the fluorinating reagent, promotes loss of fluoride from the initial fluorinated product. Trapping of the subsequent carbocation by the acetonitrile solvent in a Ritter type process gives overall nitrogen functionalisation of hydrocarbons. Amidation of hydrocarbons could also be achieved in a one-stage process by reaction of the hydrocarbon with fluorine and a Lewis acid, such as boron trifluoride-diethyl ether, in acetonitrile.
- Chambers, Richard D.,Kenwright, Alan M.,Parsons, Mandy,Sandford, Graham,Moilliet, John S.
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p. 2190 - 2197
(2007/10/03)
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- Nitration of adamantane and diamantane with nitronium tetrafluoroborate
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The slow reaction of adamantane with nitronium tetrafluoroborate at room temperature in purified, nitrile-free nitromethane or in nitroethane gives 1-nitroadamantane in 66% and 74% isolated yield, respectively. Similar reaction of diamantane gives 62% 1-and 5% 4-nitrodiamantane. Initial reaction upon aqueous workup gives 1-adamantanol with 1-fluoroadamantane, 3-fluoro-1-adamantanol, and adamantanone as byproducts. Upon prolonged reaction 1-nitroadamantane is formed in good yield. The experimental data are in accord with intermediate formation of the 1-adamantyl cation (by hydride abstraction or cleavage of initially formed 1-nitroadamantane) followed by reaction with HNO2 or NO2-formed in the reaction, giving 1-adamantyl nitrite, which then undergoes cleavage-rearrangement to give 1-nitroadamantane. A small kinetic hydrogen isotope effect of kH/kD = 1.2-1.3 is indicative of a nonlinear highly unsymmetrical transition state in the rate-determining step of the reaction.
- Olah, George A.,Ramaiah, Pichika,Rao, Chandra B.,Sandford, Graham,Golam, Rasul,Trivedi, Nirupam J.,Olah, Judith A.
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p. 7246 - 7249
(2007/10/02)
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- Multiple Pathways in the Solvolysis of 1-Adamantyl Fluoroformate
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Reactions of 1-adamantyl fluoroformate in hydroxylic solvents have been studied.In solvents of high ionizing power and relatively low nucleophilicity, such as 2,2,2-trifluoroethanol-water mixtures, the reactions parallel those of 1-adamantyl chloroformate, and only solvolysis-decomposition reaction is observed.However, differing from the reactions of the corresponding chloroformate, in other solvents appreciable amounts pf attack at acyl carbon occur, more than 90percent in 80percent aqueous ethanol.Entropies of activation for attack at acyl carbon are considerably more negative than for solvolysis-decomposition.For the solvolysis-decomposition, a Grunwald-Winstein m value of 0.70 is observed.The kCl/kF ratios for solvolysis-decomposition are in the range of 104-105, suggesting appreciable C-X bond breaking in the transition state of the rate-determining step and arguing against rate-determining formation of a 1-Ad(1+)(OCOX)(1-) ion pair.Attack at acyl carbon is analyzed in terms of the two-term Grunwald-Winstein equation, and sensitivities toward changes in nucleophilicity and ionizing power are identical to those for solvolyses of n-octyl fluoroformate, which are believed to proceed via a tetrahedral intermediate.For each of the major pathways, selectivities toward the components of binary hydroxylic solvents are reported and discussed.
- Kevill, Dennis N.,Kyong, Jin Burm
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p. 258 - 265
(2007/10/02)
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- FLUORINATION WITH CAESIUM FLUOROXYSULPHATE. PART XI. MILD FUNCTIONALIZATION OF SATURATED HYDROCARBONS
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Several hydrocarbons reacted with caesium fluoroxysulphate in acetonitrile at 35 deg C yielding mono and disubstituted products.Fluorocyclohexane, fluorocycloheptane, and 2-exo-fluoronorbornane formed in the reactions with the corresponding hydrocarbons were accompanied by up to 15percent of other unidentified fluoro products, but their amount was strongly diminished when fluoronation was performed in the presence of nitrobenzene.Fluorination of adamantane resulted in 1-fluoro, 2-fluoro, and 1,3-difluoro substituted products, with the substitution at the tertiary carbon atom strongly predominating.The presence of nitrobenzene did not influence the rate of reaction and the product distribution when the reaction was carried out in acetonitrile, while the introduction of methanol or methanol and nitrobenzene into the reaction mixture slowed down the reaction, with no evidence of the presence of methoxy derivatives.
- Stavber, Stojan,Zupan, Marko
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p. 2737 - 2742
(2007/10/02)
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- Thermically-Initiated Fluorinations at Saturated Carbon Atoms with Xenon Difluoride
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The heating of several hydrocarbons with xenon difluoride at 95-120 deg C in stainless steel reactor equipped with teflon jackets resulted in mono-, di-, and trisubstituted products.
- Zajc, Barbara,Zupan, Marko
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p. 1659 - 1661
(2007/10/02)
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- Fluorination of Adamantane Derivatives with Oxygen Difluoride
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Fluorination of adamantane and adamantane derivatives 1 with OF2 in the absence of an HF-trap gives fluoroadamantanes 2 and adamantanols 3 in varying amounts.Increasing yields of 2 are obtained in the presence of Na2CO3 as an HF-trap.In addition, the fluorooxahomoadamantanes 4b and e are formed in this reaction.The fluorination of adamantanone (5) with OF2 leads to analogous products.
- Bolte, Gerd,Haas, Alois
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p. 1982 - 1986
(2007/10/02)
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- ELECTROPHILIC ATTACK OF ELEMENTAL FLUORINE ON ORGANIC HALOGENS. SYNTHESIS OF FLUOROADAMANTANES
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Elemental fluorine acts on bromo- and iodoadamantanes in an electrophilic mode to produce the corresponding fluoroadamantanes.The course of the reaction was investigated in several solvents.It was found that the best yields of the fluoroadamantanes were obtained when Freon (CFCl3) or Freon-chloroform was used.Using methylene chloride as a solvent with iodoadamantanes-but not with the bromo derivatives-resulted in considerable amounts of the corresponding chloro compounds.
- Rozen, Shlomo,Brand, Michael
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p. 733 - 736
(2007/10/02)
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