Fluorinations organolithium reagents

Fluorinated dicarbonyl triphenylphosphoranes, easy to prepare (by trifluoro-acetylation of the stabilised ylides), have been transformed stereoselectively into / -substituted jS-trifluoromethyl alkenoates by treatment with organolithium reagents (Eq. 115) [306]. The stereoselectivity could be reversed by O-methyla-tion of the initial adduct followed by protonation [307]. 

Two unusual fluorinated phosphines, (6) and (7), have been prepared by the reactions of organolithium reagents with appropriate halogenophosphines. ... 

Reaction with Organolithium Reagents. The fluorination of vinyl lithium derivatives with NFSi has been demonstrated in good yields with complete retention of configuration about the double bond. Phenyl lithium reacts rather poorly with 7V-fluorobenzenesulfonlmlde, but more complex phenyl lithium derivatives have been fluorinated to prepare fluoro- and polyfluoro-veratraldehydes as well as complex fluorinated polyaromatic compounds. Organolithium derivatives of heterocycles have been fluorinated by reaction with NFSi at low temperature. In this manner, fluoro-pyrroles and 2-fluoro-5-methylthleno[3,2-b]pyrldlne are prepared from their corresponding llthlo-parent compounds (eq 16). ... 

Reaction with Organolithium Reagents. Organolithium derivatives of a variety of heteroaromatics have been fluorinated with NFSi. The direct C-H lithiation at the most reactive position of heteroarene compounds was conducted at low temperature with either t-BuLi, w-BuLi, or LDA in the presence of NFSi to provide regioselective fluorination. This way, oxazoles (eq 34), benzo[i>]thiophene-5,6-dicarbaldehyde, spiro[4,5-dihydrothieno[2,3-c]pyran-7,4 -piperidine, dibenzo-... 

Scheme 15.59 Aryl fluorination through organolithium reagents.

The a-fluorophosphonate moiety has previously been introduced utilizing thermally unstable organolithium reagents166,167 and fluorinating agents such as DAST168. (EtO)2P(0)CFHZnBr is thermally stable, scalable and avoids the use of expensive and hazardous fluorination reagents. 

See Other FLUORINATED ORGANOLITHIUM COMPOUNDS, GRIGNARD REAGENTS, HALO-ARYLMETALS... 

See other GRIGNARD reagents, halo-arylmetals, fluorinated organolithium COMPOUNDS... 

Fig. 28.25 Schematic representation of fluorination of a carbon nanotube, and reaction of a fluoro-substituted derivative with organolithium and Grignard reagents.

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