An approach to novel fused triazole or tetrazole derivatives starting from benzimidazo[1,2‐ a ]quinazoline‐5(7 H )‐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(7 H )‐one 2a and 5,7‐dihydro‐5‐oxopyrido[3′,2′:5,6]pyrimido[1,2‐ a ]benzimidazole 2b for the construction of novel polyhetero‐cyclic 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 tri‐azoles 8a,b , isomers of 7a,b , resulting from the occurrence of a Dimroth rearrangement.