Reactions of Chiral Imines with Heteroatom-substituted Dienes

Reactions of Chiral Imines with Heteroatom-substituted Dienes [Pg.81]

Reactions of imines derived from valine tert-butyl ester with Brassard s diene proceed highly stereoselective in the presence of Lewis acids, such as EtAlCl2, at low temperature. Removal of the chiral auxiliary is achieved via a Curtius rearrangement. [Pg.81]

Lewis acid-catalyzed (EtAlCla, ZnClz) aza Diels-Alder reaction of imines derived from amino acid esters or carbohydrates with Danishefsky s diene provide precursors of chiral piperidine alkaloids. When using imines derived from 0-pivaloylated glycosylamines and ZnCl2 as Lewis acid, highly diastereoselective tandem-Mannich-Michael reactions are observed. The carbohydrate moiety is easily removed by treatment with HCl/MeOH. By employing galactopyranosylamine or arabinosylamine derivatives both enantiomeric series are readily available. [Pg.81]

3 Reactions of Achiral Imines with Chiral Heteroatom-substituted Dienes [Pg.83]

Chiral 2-amino-l,3-butadienes derived from 2-(methoxymethyl)pyrrolidine and a-oxo enamines undergo cycloadditions with jV-silylimines in the presence of ZnCl2 to yield 4-piperidinones stereoselectively upon subsequent hydrolysis with aqueous NaHCOs. [Pg.83]

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