SYNTHESIS, STRUCTURE, AND STEREOSELECTIVE REACTION OF A CHIRAL HYDROXY-STABILIZED METAL-FREE ENOLATE

The reaction of acetophenone with tetrabutylammonium hydroxide affords the tetrabutylammonium enolate of phenyl (2-hydroxy-2-phenyl)propyl k etone. The crystal structure of this chiral enolate shows intramolecul ar hydrogen bonding between the hydroxyl group and the enolate oxygen atom. Furthermore, the alpha-methylene units of the ammonium counterio n form hydrogen bonds to the basic enolate C and O atoms and to the O atom of the hydroxy group. This three-point bonding occurs selectively on the Re,Re side, a phenomenon which may be responsible for the dire ction of diastereo-selectivity in the epoxide-forming reaction of the enolate with N-bromosuccinimide.