- FLP-Catalyzed Monoselective C-F Functionalization in Polyfluorocarbons at Geminal or Distal Sites
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We report frustrated Lewis pair (FLP)-catalyzed monoselective C-F activation in a range of aliphatic polyfluorocarbons with equivalent geminal and distal C-F positions. This methodology can be applied to aromatic-, ether-, thioether-, and alkyl-supported fluoromethyl groups. We expand the range of FLP base partners that work with monoselective C-F activation to include sulfide. The activated products can be subsequently functionalized via SN2 substitutions, photoredox-alkylations, and Suzuki couplings.
- Gupta, Richa,Mandal, Dipendu,Jaiswal, Amit K.,Young, Rowan D.
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supporting information
p. 1915 - 1920
(2021/04/05)
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- Triazolopyrimidines
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Novel triazolopyrimidines of the formula in which R1, R2, R3 and X have the meanings given in the description, a process for preparing these novel substances and their use for controlling undesirable microorganisms and animal pests. Novel amines of the formula in which R4 has the meanings given in the description, and processes for their preparation.
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- Method for detecting dopaminergic diseases using fluorine-18 radiolabelled D2 dopamine receptor ligands
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Abnormalitites in the distribution of a dopamine D 2 receptors in humans and other mammals are detected by(1) administering to a human or other mammal an amount of a 18 F-radiolabelled compound sufficient to be detected by a positron emission sensitive means for imaging, said compound having affinity for said receptors selected from the group consisting of optically active or racemic compounds represented by the general formula: STR1 (2) forming at least one image showing the distribution of the radiolabelled compound within the human or other mammal using a positron emission-sensitive means for imaging; and(3) determining normality of the concentrations or distribution by comparing the image with an image showing the normal concentrations and distribution of the receptors in humans or mammals of the same species wherein R1-R4, n and m- are as set forth in the specification.
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- REACTIONS OF HALOGENS FLUORIDES. VIII. SUBSTITUTIVE FLUORINATION OF BROMINE-CONTAINING ALKANES AND ESTERS WITH BROMINE TRIFLUORIDE
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The conditions were found for selective liquid-phase substitutive fluorination of bromine-substituted alkanes and esters with pure bromine trifluoride, in which all three fluorine atoms of the BrF3 molecule are used effectively in the fluorination.The exchange of bromine for fluorine in monobromohalogenoalkanes is nonstereospecific and is in a number of cases accompanied by skeletal rearrangements, hydride shifts, and migration of the halogen.A carbocationic mechanism of fluorination is discussed.
- Chuvatkin, N. N.,Kartashov, A. V.,Morozova, T. V.,Boguslavskaya, L. S.
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p. 237 - 242
(2007/10/02)
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- A Rapid and Efficient Method for the Fluoroalkylation of Amines and Amides. Development of a Method Suitable for Incorporation of the Short-Lived Positron Emitting Radionuclide Fluorine-18
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We have described a two-step method for the preparation of fluoroalkyl-substituted amines and amides.The sequence involves fluoride ion displacement of a haloalkyl trifluoromethanesulfonate (triflate), followed by fluoroalkylation of the heteroatom system (amine or amide) by the fluoroalkyl halide.Alternatively, the fluoroalkyl halide can be prepared by halofluorination of a terminal olefin.These reactions have been used to prepare various fluoroalkyl derivatives of N-phenylpiperazine and N-fluoroalkyl derivatives of the neuroleptic agent spiperone (7).The sequence is rapid, convenient, and efficient, even when fluoride ion is the limiting reagent.Therefore, it is readily adaptable to the preparation of a variety of compounds labeled with the short half-life (t1/2 = 110 min) positron-emitting radionuclide fluorine-18.
- Chi, Dae Yoon,Kilbourn, Michael R.,Katzenellenbogen, John A.,Welch, Michael J.
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p. 658 - 664
(2007/10/02)
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- Replecement of the carboxylic acid function with fluorine
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Replacement of a carbonyl function by fluorine, fluorodecarboxylation, is a new process that can be accomplished by the reaction of alkanoic acids with xenon difluoride.Primary, tertiary, and benzylic acids perform best in the reaction, which is conducted at room temperature in methylene chloride or chloroform solution.A reaction mechanism is proposed in which the acid is initially converted to a fluoroxenon ester, RCO2XeF.The esters of the primary and secondary acids react by nucleophilic displacement by fluoride, as evidenced by incorporation of 18F- and no reactions common to free radicals or carbocations.The esters of the tertiary and benzylic acids react by converting to free radicals that can be further oxidized to carbocations.Thus incorporation of 18F- and racemization are observed with α-methoxy-α-trifluoromethylphenylacetic acid.Hydroxyl and amino functions inhibit the reaction.Aromatic and vinylic acids do not react.
- Patrick, Timothy B.,Johri, Kamalesh K.,White, David H.,Bertrand, William S.,Mokhtar, Rodziah,et al.
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p. 138 - 141
(2007/10/02)
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- Substituted Terminal Alkyl Groups and Their Prospects in Liquid Crystal Chemistry
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Polar substituents may be attached to the terminal alkyl groups of rodlike mesogens to increase their ε and to give a positive or negative Δε.The mesomorphic behaviour of some biphenyls, phenylcyclohexanes and bicyclohexanes with substituted alkyl groups was studied and compared to that of the corresponding unsubstituted compounds.In the first series no conclusive results could be obtained due to the relatively high melting points and low clearing points of the investigated compounds.In the phenylcyclohexanes and bicyclohexanes, substituents in ω-position were found to enhance the clearing temperature.In contrast, cyano groups in α-position depressed the clearing point.However, this depression is still much less than that caused by the introduction of lateral substituents in the phenyl moieties of the rigid core.
- Osman, Maged A.
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p. 353 - 360
(2007/10/02)
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- REACTIONS OF CHLORINE MONOFLUORIDE. VI. RELATIVE RATES OF SUBSTITUTIVE FLUORINATION OF BROMINE-SUBSTITUTED ALKANES. HYDRIDE SHIFTS AND OTHER MIGRATIONS DURING FLUORINATION
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The relative rates of substitutive fluorination of bromoalkanes with various structures by chlorine monofluoride in a nonpolar medium at 20-40 deg C were investigated by the method of competing reactions.Halogen atoms vicinal with the substituted bromine greatly reduce the fluorination rate.The reactivity of the secondary bromides decreases in the order (CH3)2CHBr>>CH3CHBrCH2Cl>>CH2ClCHBrCH2Cl.The geminal halogen atoms have little effect on the rate of substitutive fluorination.The fluorination rates of the bromoalkanes CH2BrCH2Br, CH2BrCHClBr, and CH2BrCCl2Br are in ratios 10:3:1 respectively, while the fluorination rate of CH3CHClBr is much higher than that of CH2ClCH2Br.As a rule the debromination of primary bromides containing vicinal halogens (Br, Cl) is accompanied by migration of the latter and gives fluorides with iso structures.Hydride shifts take place in cases where stable tertiary or secondary carbocations are formed as a result of migration of the hydride; for example, the fluorination of CH3CHFCH2Br leads to the geminal difluoroalkane CH3CF2CH3.The mechanism of substitutive fluorination is discussed.
- Morozova, T. V.,Chuvatkin, N. N.,Panteleeva, I. Yu.,Boguslavskaya, L. S.
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p. 1255 - 1263
(2007/10/02)
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