Specific Enolates from α-Amino Ketones

Article abstract of DOI:10.1021/jo01300a009

The enolization of 11 tertiary α-amino ketones was investigated under three different conditions (kinetic base, thermodynamic base, thermodynamic acid) to determine the directionality of such enolates for application to alkaloid synthesis.The ketone structural variables examined were the geometry of the amine nitrogen lone pair-carbonyl array and the electronic nature of the nitrogen substituent.With the exception of 3-pyrrolidinones, increasing the electron-withdrawing nature of the nitrogen increases the amount of enolization toward nitrogen (3, 6, and 9 or 21, 24, and 27).N-Alkyl-substituted amino ketones (3, 12, 21, 33) under kinetic base conditions yield enolate distributions similar to those of the corresponding all-carbon compounds.N-Carbamato-substituted amino ketones (6, 24, 27, 30) enolize predominantly toward nitrogen under all conditions.The 3-pyrrolidinones 12, 15, and 18 afford enolates away from nitrogen under all conditions.