Asymmetric Fluorination of Enolates with Nonracemic <i>N</i>-Fluoro-2,10-Camphorsultams

Abstract

The asymmetric “electrophilic” fluorination of tertiary enolates by nonracemic N -fluoro-2,10-camphorsultams 3 affords quaternary α-fluoro carbonyl compounds in modest yield and ee. The highest asymmetric induction was observed for the fluorination of the sodium enolate of 2-methyl-1-tetralone ( 8a ) by (−)- N -fluoro-2,10-(3,3-dichlorocamphorsultam) ( 3b ) to give ( S )-(+)-2-fluoro-2-methyl-1-tetralone ( 9a ) in 70% ee. The absolute configuration was established by X-ray crystallography of the corresponding diastereomeric β-hydroxy sulfoximine prepared from (±)- 9a and the Johnson reagent. The asymmetric induction exhibited by 3 is opposite to that of the closely related enolate hydroxylation reagents nonracemic (camphorylsulfonyl)oxaziridines 4 . The N -fluoro sultams 3 were prepared by fluorination (10% F 2 /N 2 ) of the corresponding sultams 5 .