Effect of molecular sieves on the formation and acid-catalysed mono- and bis-cyclization of N-arylimines: easy entry to polycyclic ring systems by a novel cascade reaction

Abstract

The synthesis of substituted octahydroacridines 14–17 and N-arylcyclohexylamines 18–20 from arylamines 5–8 is described. It was found that the isolation of the imines 10–13 and that Lewis acid catalysis could be avoided if molecular sieve beads were used instead of powder. The sequential molecular sieves-catalysed imine-formation/cyclization could be extended to a novel one-pot biscyclization of aryldiamines 29–31 with separated aromatic systems. However, the conversion of aryldiamines 36 and 38 with two amino groups on the same aromatic system into the corresponding biscyclization products 23 and 45 required a two-step procedure under harsher conditions.