The first catalytic, enantioselective vinylogous Mannich reaction of acyclic silyl dienolates is reported. A second-generation 2,2'-dihydroxy-1,1'-binaphthyl (BINOL)-based phosphoric acid has been developed and further optimized as an enantioselective organocatalyst. Upon protonation of the imines, chiral contact ion pairs are generated in situ and attacked highly diastereoselectively by the nucleophile. gamma-Substituted silyl dienolates that lead to more highly substituted Mannich products with a second stereogenic center in good diastereoselectivity have been employed in these reactions. The reaction path has been elucidated with NMR spectroscopy and mass spectrometry, which suggest that the protic reaction medium found to be optimal in these reactions serves to trap the cationic silicon species as silanol. A crystal structure of a phosphoric acid bound imine was obtained that provides insight into the binding mode and a rationale for the stereochemical course of the reaction.

The Broensted Acid Catalyzed, Enantioselective Vinylogous Mannich Reaction.-The three-component Mannich reaction of aromatic, heteroaromatic, or aliphatic aldehydes with amine (II) and silyl dienolate (III) (Z:E=2.5:1) in the presence of the optimized axially chiral phosphoric acid diester PHA provides δ-amino α,β-unsubstituted esters (IV) and (VI). The protic reaction medium is found to be optimal to trap the formed cationic silicon species as silanol. Silyl dienolate (VIII) (1E:1Z=1:1.5) undergoes a two-component Mannich reaction with aromatic or heteroaromatic imines to give under similar conditions products bearing two stereogenic centers. Whereas the geometry of the double bond directly attached to the acetal moiety of the dienolate has no effect on the stereochemical outcome, the geometry of the attached propenyl group significantly influences the yield and stereoselectivity. The (3Z)-analogue of compound (VIII) furnishes only low yields and stereoselectivities. -(SICKERT, M.; ABELS, F.; LANG, M.; SIELER, J.; BIRKEMEYER, C.; SCHNEIDER*, C.; Chem.

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