Halogenoalkyl Isocyanates as Bifunctional Reagents in an Aza-Wittig/Heterocyclization Reaction on the Solid Phase: Efficient Entry into New Tetracyclic Benzimidazole Systems

An efficient one-pot procedure for the solid-phase synthesis of new tetracyclic 1,3,5-triazino[1,2-a]benzimidazolium derivatives starting from resin-bound benzimidazoles is described. The synthetic strategy involves an unprecedented one-pot Aza-Wittig/heterocyclization/substitution reaction sequence using halogenoalkyl isocyanates. The structure of the tetracyclic ring system was determined by two-dimensional NMR experiments and X-ray analysis.