An approach to novel fused triazole or tetrazole derivatives starting from Benzimidazo[1,2-a]quinazoline-5(7H)-one and 5,7-Dihydro-5-oxopyrido[3',2':5,6]pyrimido[1,2-a]benzimidazole

The synthetic potential of the title compounds benzimidazo[1,2-a]quinazoline-5(7H)-one 2a and 5,7-dihydro-5-oxopyrido[3′,2′:5,6]pyrimido[1,2-a]benzimidazole 2b for the construction of novel polyheterocyclic frameworks is reported. Compounds 2a,b, by conversion into their thio analogues 3a,b, were used for the synthesis of tetrazole (5a,b) and triazole (7a,b) derivatives, as well as for an unexpected synthesis of triazoles 8a,b, isomers of 7a,b, resulting from the occurrence of a Dimroth rearrangement.