Synthesis and reactivity of some imidazo‐, triazolo‐ and tetrazolo‐isoquinoline derivatives

1‐Acetylirrüno‐3‐methyl‐1H‐isochromene‐4‐carbonitrile, 1 , reacts with glycine ethyl ester under basic conditions to give an imidazo2,1‐a]isoquinoline derivative, while reaction with hydrazine hydrate in 1,4‐dioxane, with further chemistry, provides access to 1,2,4]triazolo5,1‐a]isoquinoline, 1,2,4]triazolo3,4‐a]isoquinoline and tetrazolo5,1‐a]isoquinoline analogs. Benzene ring nitration and radical bromination of substituent methyl groups were investigated in the four tricycles, with some different positional reactivities being found. Two bromomethyl derivatives so produced were oxidised; ethyl 2‐bromomethyl‐6‐cyano‐5‐methylimidazo2,1‐a]isoquinoline‐3‐carboxylate gave the anticipated ethyl 6‐cyano‐2‐formyl‐5‐methylimidazo2,1‐a]isoquinoline‐3‐carboxylate (which reacted further with hydrazine to form a new system, 8,9‐dihydro‐6‐methyl‐8‐oxopyridazino4′,5′:4,5]imidazo2,1‐a]isoquinoline‐5‐carbonitrile), while 5‐bromomethyl‐2‐methyl1,2,4]triazolo5,1‐a]isoquinoline‐6‐carbonitrile unexpectedly gave directly another new system, 5,6‐dihydro‐5‐hydroxy‐2‐methyl‐7H‐pyrrolo3,4‐c]1,2,4]triazolo5,1‐a]isoquinolin‐7‐one.