Aldehydes nucleophiles

Some organic reactions can be accomplished by using two-layer systems in which phase-transfer catalysts play an important role (34). The phase-transfer reaction proceeds via ion pairs, and asymmetric induction is expected to emerge when chiral quaternary ammonium salts are used. The ion-pair interaction, however, is usually not strong enough to control the absolute stereochemistry of the reaction (35). Numerous trials have resulted in low or only moderate stereoselectivity, probably because of the loose orientation of the ion-paired intermediates or transition states. These reactions include, but are not limited to, carbene addition to alkenes, reaction of sulfur ylides and aldehydes, nucleophilic substitution of secondary alkyl halides, Darzens reaction, chlorination... [Pg.370]

TPP-dependent decarboxylation of a-keto acid to aldehyde nucleophilic addition of TPP anion on to aldehyde then allows removal of aldehydie proton which has become acidic... [Pg.162]

N. S. Chowdari, D. B. Ramachary, C. F. Barbas, III, Synlett 2003, 1906-1909. Organocatalysis in ionic liquids highly efficient L-prohne-catalyzed direct asymmetric Mannich reactions involving ketone and aldehyde nucleophiles. [Pg.67]