2-Cyano acetates, fluorination

The catalytic enantiomeric fluorination of a-cyano acetates catalyzed by the chiral palladium complex was also reported leading to a-cyano-a-fluoro acetates with excellent enantiomeric excesses (up to 99% ee). °... 

Kim HR, Kim DY. Catalytic enantioselective fluorination of a-cyano acetates catalyzed by chiral palladium complexes. Tetrahedron Lett. 2005 46 3115-3117. 

The formation of ethyl cyano(pentafluorophenyl)acetate illustrates the intermolecular nucleophilic displacement of fluoride ion from an aromatic ring by a stabilized carbanion. The reaction proceeds readily as a result of the activation imparted by the electron-withdrawing fluorine atoms. The selective hydrolysis of a cyano ester to a nitrile has been described. (Pentafluorophenyl)acetonitrile has also been prepared by cyanide displacement on (pentafluorophenyl)methyl halides. However, this direct displacement is always aecompanied by an undesirable side reaetion to yield 15-20% of 2,3-bis(pentafluoro-phenyl)propionitrile. 

A group of Russian workers [22 to 27] reported on the fluorination of mixtures of solid amines, amides, or cyano compounds with KF or CaF2. The reactions were carried out in a stream of F2 diluted with N2 at about -10 to +10°C. NF3 was one of the main products and was accompanied by fluorinated fragments of the compounds treated. The N-containing compounds studied include aliphatic amine hydrochlorides [22, 23], the amides of trifluoro- and difluoro acetic acid [24], potassium cyanate [25], silver and potassium thiocyanate [26], and a acetonitrile boron trifluoride complex [27]. 

Unlike the chiral, neutral N-F reagents, the [N-F] ammonium salts of cinchona alkaloids are employed for the fluorination of a number of substrates ketone and ester enolates, (3-keto esters, a-cyano esters, a-nitro esters, a-amino esters, silyl enol ethers, enol acetates, nitrile anions, and... 

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