New Chiral Isoquinolinium Salt Derivatives from Chiral Primary Amines via Zincke Reaction

摘要

Recent publications from our laboratory have shown that the Zincke reaction with chiral primary amines provides a very practical entry to new pyridinium salt derivatives of interest in asymmetric synthesis. Selective reduction of these salts to 1,2- or 1,4-dihydropy-ridines, which could be equilibrated to dihydropyridinium salt equivalents, afforded versatile intermediates for the enantioselective synthesis of alkaloids containing substituted six-membered nitrogen heterocycles. We now describe the extension of this methodology to the syntheses of chiral isoquinolinium salt derivatives of practical interest for the asymmetric synthesis of substituted tetrahydroisoquinolines.