102410-95-7Relevant academic research and scientific papers
Mechanistic Studies of Fluorodecarboxylation with Xenon Difluoride
Patrick, Timothy B.,Khazaeli, Sadegh,Nadji, Sourena,Hering-Smith, Katy,Reif, Dirk
, p. 705 - 708 (1993)
The reaction of xenon difluoride with primary carboxylic acids involves a free-radical mechanism.Trifluoroacetic acid (1) decarboxylates in benzene to give (trifluoromethyl)benzene (2). 6-Hexenoic acid (3) produces a free radical in a radical clock reaction in which the kabs (25 deg C) for XeF2 was determined as 1.1 * 106 M-1 s-1.The primary radical from hexanoic acid was spin-trapped to give ESR signals diagnostic for the alkyl radical.Secondary acids were shown to proceed through a trivalent intermediate, but its exact nature was not proven.The acid 6 gave a rearranged product (7) characteristic of carbocations, whereas the diacid 8 gave difluoro compounds without stereoselectivity.The tertiary bicyclic acids 13 and 15 gave products only from solvent hydrogen abstraction strongly indicative of free radicals.
Nucleophilic (Radio)Fluorination of Redox-Active Esters via Radical-Polar Crossover Enabled by Photoredox Catalysis
Webb, Eric W.,Park, John B.,Cole, Erin L.,Donnelly, David J.,Bonacorsi, Samuel J.,Ewing, William R.,Doyle, Abigail G.
, p. 9493 - 9500 (2020/05/18)
We report a redox-neutral method for nucleophilic fluorination of N-hydroxyphthalimide esters using an Ir photocatalyst under visible light irradiation. The method provides access to a broad range of aliphatic fluorides, including primary, secondary, and tertiary benzylic fluorides as well as unactivated tertiary fluorides, that are typically inaccessible by nucleophilic fluorination due to competing elimination. In addition, we show that the decarboxylative fluorination conditions are readily adapted to radiofluorination with [18F]KF. We propose that the reactions proceed by two electron transfers between the Ir catalyst and redox-active ester substrate to afford a carbocation intermediate that undergoes subsequent trapping by fluoride. Examples of trapping with O- and C-centered nucleophiles and deoxyfluorination via N-hydroxyphthalimidoyl oxalates are also presented, suggesting that this approach may offer a general blueprint for affecting redox-neutral SN1 substitutions under mild conditions.
Replecement of the carboxylic acid function with fluorine
Patrick, Timothy B.,Johri, Kamalesh K.,White, David H.,Bertrand, William S.,Mokhtar, Rodziah,et al.
, p. 138 - 141 (2007/10/02)
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.
