Generation and dienophilic properties of 1‐benzyl‐1H‐1,2,3‐triazolo[4,5‐d]pyridazine‐4,7‐dione

Abstract
1‐Benzyl‐5,6‐dihydro‐1H,2,3‐triazolo[4,5‐d]pyridazine‐4,7‐dione (1) by oxidation with lead tetraacetate afforded the corresponding triazolopyridazine‐4,7‐dione 2 as the intermediate, which was trapped with several dienes giving the hetero‐Diels‐Alder adducts 3 in good yields. The structure of the cycloadduct 3a was determined by X‐ray analysis.