21 Asymmetric Synthesis Involving Dynamic Enantioselective …
441
Fig. 21.4 Asymmetric isomerization followed by dynamic crystallization under achiral conditions
crystallization could then be carried out using the racemic mixture of the trans isomer
as a starting material, and deracemization to the trans-26c of high enantiomeric purity
was observed.
21.3.2 Asymmetric Synthesis Using Reversible aza-Michael
Addition Reaction Followed by Attrition-Enhanced
Deracemization
Vlieg et al. succeeded in obtaining β-aminoketone 27 in 100% ee by applying the
Viedma ripening method to the reversible aza-Michael addition reaction of anisidine
to an enone (Fig. 21.5) [57]. When anisidine was reacted with an enone in ethanol,
conglomerate adduct 27 crystallized. The reaction mixture was kept in suspension
with stirring in the presence of DBU, and deracemization was promoted through the
reverse reaction leading to one-handed enantiomorphic crystals.
441
Fig. 21.4 Asymmetric isomerization followed by dynamic crystallization under achiral conditions
crystallization could then be carried out using the racemic mixture of the trans isomer
as a starting material, and deracemization to the trans-26c of high enantiomeric purity
was observed.
21.3.2 Asymmetric Synthesis Using Reversible aza-Michael
Addition Reaction Followed by Attrition-Enhanced
Deracemization
Vlieg et al. succeeded in obtaining β-aminoketone 27 in 100% ee by applying the
Viedma ripening method to the reversible aza-Michael addition reaction of anisidine
to an enone (Fig. 21.5) [57]. When anisidine was reacted with an enone in ethanol,
conglomerate adduct 27 crystallized. The reaction mixture was kept in suspension
with stirring in the presence of DBU, and deracemization was promoted through the
reverse reaction leading to one-handed enantiomorphic crystals.