A Directed Stereoselective Aldol Reaction: Simple Synthesis of Enantiopure δ-Hydroxy-β-enamino Ketones by Condensation of Homochiral β-Enamino Ketones with Aldehydes and Ketones.

Abstract A simple synthesis of enantiopure anti -δ-Hydroxy-β-enamino ketones 3 by condensation of homochiral lithium dianions derived from β-enamino ketones 1″ with aldehydes and ketones is reported. The mechanism for the directed enantioselective aldol reaction was investigated. The anti δ-hydroxyenaminone 3 is obtained as the major diastereomer through an open transition state. In acidic conditions the δ-hydroxyenaminones 3 are cyclized to 4-imino-2,3-dihydropyranones 4 which are instable and isomerize spontaneously to γ alkylidenenaminones 5 .