Fluorocarbonyl compounds

Nitro compounds are oxidized at carbon bonded to nitro group 2-nuoronitro compounds and silyl mtronates are converted to 2-fluorocarbonyl compounds by ceric ammonium salt [7l (equation 73)... 

Chlorinated oxiranes can be treated with silver(I) tetrafluoroborate to yield the corresponding a-fluorocarbonyl compounds as major products and the isomeric a-chlorocarbonyl compounds as minor products.74... 

Thallium(I) fluoride is, furthermore, used for the conversion of acyl chlorides to acyl fluorides6 and the preparation of a-fluorocarbonyl compounds.7,8... 

Many fluorinations by electropositive fluorine reagents produce a-fluoro carbonyl compounds as the final result An extensive review exists on the preparation of a-fluorocarbonyl compounds [10]. Also, electropositive reagents are used, widely in the preparation ofISF-labeled radioactive materials required in positron emission tomography for biomedical research Excellent reviews are available on fluonne-18 labeling [11, 12]. 

Aziridines behave similarly to epoxides and were used for making aliphatic and steroidal fluoroamines (equations 12 and 13)25, the latter via trans diaxial opening26. Azirines were also treated with HF Py producing a,a -difluoroamines or a-fluorocarbonyl compounds depending on the reaction solvent (equation 14)27. 

Obviously, CsF is a better source for nucleophilic fluorine than any other metal fluoride and, indeed, it is used to attack fluorocarbonyl compounds on route to make hypofluorites... 

Group 1 metal fluorides have been employed as column packings for the determination of COF2 (and other fluorocarbonyl compounds) in mixtures with tetrafluoroethene [967]. By using a column composed of CsF supported upon CaFj, the tetrafluoroethene is not chemisorbed and is eluted rapidly. The fluorocarbonyl compounds (CF3)jC=0 (b.pt. -28 C), CF3C(0)F (b.pt. -59 C), and COF (b.pt. -84.6 C), however, are eluted in reverse order of boiling temperatures, so that carbonyl difluoride is eluted last [967]. The chemisorption arises from the reversible chemical process [1692] ... 

Another stereoelectronic effect induced by electronegative substituents is the "Anh-Eisenstein effect [44] (Scheme 4.17) which can be of particular importance to the stereochemical outcome of enzymatic reactions involving fluorinated substrates [45]. In a-fluorocarbonyl compounds nucleophilic attack of the carbonyl group occurs preferentially anti to the fluorine substituent [46]. The resulting, unusually high stereospecificity, e.g. in some enzymatic reactions of fluorinated substrates [45], cannot be explained by the slightly different steric demands of hydrogen and fluorine alone. 

Unsaturated halogenated compounds with a central C = C or C = C bond undergo cleavage on oxidation in the middle of the molecule and form two carboxylic acids without loss of a carbon atom. The reaction mechanism of the oxidation of internal fluoroalkenes by potassium permanganate includes hydroxylation of the C = C bond in 2 by permanganate, accompanied by dehydrofluorination of the geminal fluoroalkane-1,2-diol 3 and formation of an intermediate fluorocarbonyl compound 4 oxidative cleavage of the C-C bond in 4 leads to the final products 5.1... 

S. Rozen and R. Filler, a-Fluorocarbonyl Compounds and Related Chemistry, Tetrahedron, 1985, 4J, 1111. 

Monofluorination of Enolates. /V Fluorosultam (1) has been successfully used to prepare a-fluorocarbonyl compounds by electrophilic fluorination starting, for example, from disubstituted enolates derived from ketones, esters, and -dicarbonyl compounds (eqs 13). The related /V-fluorosulfonamide reagents ... 

Fluorination of Enolates and Silyl Enol Ethers. iV-fluoro-Af-(phenylsulfonyl)henzenesulfonamide (1) can be used successfully to prepare a-fluorocarbonyl compounds starting from esters, ketones, or 8-dicarbonyl precursors by electrophilic fluorination of the corresponding enolates (eqs 1-3) or silyl enol ethers (eq 4). Diastereoselective fluorination of enolates with 1 has recently been reported. ... 

Nitrosyl fluoride also catalyses the addition of chlorine monofluoride (and of fluorine) across G=0 bonds in fluorocarbonyl compounds, the reaction apparently proceeding via initial formation of a-fluoro-nitrites. Apparently, no reaction occurs between carbon dioxide and chlorine monofiuoride in the presence of caesium fluoride in the temperature range -78 to 80 G [c/. CO3 + 2F °S GF COF), (100%)], but thionyl... 

BiomimetiCy Reducing Agent-Free Reductive Amination of Fluorocarbonyl Compounds Practical Asymmetric Synthesis of Enantiopure Fluoroamines and Amino Acids... 

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