Ketones enantioselective fluorination, enolates

The Behenna-Stoltz protocol was soon applied to a-fluoroketones. As shown in Scheme 5.26, the silyl enol ethers 80 of 2-fluoro-indanone, tetralone-, and ben-zosuberone can be reacted with allyl or methallyl carbonate to give the tertiary a-fluorinated ketones 81 in 83-95% ee [43]. The procedure that was also applied to an allylation of 4,4-dimethyl-6-fluorocyclohexenone offers an alternative to the enantioselective fluorination of enolates on the one hand and the decarboxylative allylation of fluorinated P-keto esters on the other hand vide infra). 

Fluorination of Ketone Enolates. (+)-lV-Fluoro-2,10-(3,3-dichlorocamphorsultam) (1) reacts with ketone enolates to give a-fluoro ketones. For example, reaction of the sodium enolate of propiophenone 2 gives a-fluoropropiophenone 3 in 41% isolated yield (eq 1). No enantioselectivity, however, is observed due to racemization of the product under the reaction conditions. When a tertiary substituted ketone such as a-methyltetralone (4) is employed, the desired a-fluorinated product (S)-(-)-S is obtained in 76% ee and 53% isolated yield (eq 2). In this reaction, (+)-l was found to be more reactive, affording higher yields and better enan-tioselectivities than its parent (-)-N-fluoro-2,10-camphorsultam i.e., 35% ee, < 5% yield. ... 

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