Scandium Pentafluorobenzoate-Catalyzed Unexpected Cascade Reaction of 2‑Aminobenzaldehydes with Primary Amines: A Process for the Preparation of Ring-Fused Aminals

An
unexpected cascade reaction of 2-aminobenzaldehydes with arylamines
catalyzed by scandium pentafluorobenzoate [Sc­(Pfb)3] was
reported as a facile strategy for the efficient synthesis of a novel
class of polycyclic ring-fused aminals N-substituted-6,7,11b,13-tetrahydro-6,12-[1,2]­benzenoquinazolino­[3,4-a]­quinazolin-13-amines 1. Under similar conditions,
a series of the analogues of Tröger’s base, 13-substituted-5,6,11,12-tetrahydro-6,12-epiminodibenzo­[b,f]­[1,5]­diazocines 2 were obtained when the
arylamines were replaced by methanamines. A possible mechanism for
the formation of 1 and 2 was proposed.