Enolate anions from active hydrogen compounds

Alkylation Alkylation of the phenylindanone 31 with catalyst 3a by the Merck group demonstrates the reward that can accompany a careful and systematic study of a particular phase-transfer reaction (Scheme 10.3) [5d,5f,9,36], The numerous reaction variables were optimized and the kinetics and mechanism of the reaction were studied in detail. It has been proposed that the chiral induction step involves an ion-pair in which the enolate anion fits on top of the catalyst and is positioned by electrostatic and hydrogen-bonding effects as well as 71—71 stacking interactions between the aromatic rings in the catalyst and the enolate. The electrophile then preferentially approaches the ion-pair from the top (front) face, because the catalyst effectively shields the bottom-face approach. A crystal structure of the catalyst as well as calculations of the catalyst-enolate complex support this interpretation [9a,91]. Alkylations of related active methine compounds, such as 33 to 34 (Scheme 10.3), have also appeared [10,11]. 

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