Fluoroketone catalysts

A second class of catalysts comprises perfluorinated ketones such as hexafluoro-acetone [38] and perfluoro-2-octanone ]39]. This class of catalyst is assumed to reversibly form peroxyhemihydrates when exposed to hydrogen peroxide ]40] the latter are the active oxygen-transfer agents. Oxygen transfer to the substrate is accompanied by formation of the ketone s hydrate, which, in equilibrium, regenerates the fluoroketone catalyst. 

Hexafluoroacetone and hydrogen peroxide in buffered aqueous solution epoxi-dizes alkenes and allylic alcohols. Other fluoroketones also function as epoxi-dation catalysts.Af,Af-dialkylpiperidin-4-one salts are also good catalysts for... 

The enantioselective hydrogenation of fluoroketones on cinchonidine modified Pt-alirmina in toluene with and without trifluoroacetic acid was also studied, and it was proposed that the compounds responsible for the chiral induction were the intermediate complexes, the structures of which depended on whether hydrogenation was performed with or without TFA An unexpected change in the sense of enanatioselectivity was observed in the hydrogenation of ethyl pyruvate (EtPy) over Zreto-isocinchonine modified Pt-alumina catalysts, where (A)-(-)-ethyl lactate was the major product in toluene, while (5)-(+)-EtLt was formed in AcOH... 

Fluorinated alcohols, and in particular HFIP, have also proven beneficial for epoxidations of alkenes using persulfate (Oxone) as the terminal oxidant and fluoroketones as catalysts [9, 10]. Under these conditions, the fluorinated ketones are converted to dioxiranes, which are the active epoxidizing spedes. Typical catalysts... 

The use of a-fluoroketone derivatives, as catalysts for the aforementioned epoxidation, has been less effective. So, the epoxidation of methyl cinnamate using the tropinone derivative 63 [69] gave the expected epoxide with modest results (33%, 64% ee). The use of organocatalysts 64 [70] did not improve the enantioselectivity but did improve chemical yields (up to 97%). 

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