A new selective preparation of ethyl 7‐aminopteridine‐6‐ carboxylate derivatives and related compound

A series of ethyl 7‐amino‐2,4‐dioxopteridine‐6‐carboxylates 4 and ethyl 7‐amino‐4‐oxo‐2‐thioxopteridine‐6‐carboxylates 5 , of interest biologically, has been prepared in one step from the reaction of such vicinal ‐diamines as 1,3‐dialkyl‐5,6‐diaminouracils 2 or 1,3‐dialkyl‐5,6‐diamino‐2‐thiouracils 3 with diethyl ( E )‐2,3‐dicyanobutenedioate ( 1 ). Moreover, ethyl 3‐amino[1,2,4]triazino[2,3‐ a ]‐1 H ‐benzimidazole‐2‐carboxylate ( 11 ) was also obtained from the reaction between 1,2‐diamino‐1 H ‐benzimidazole ( 10 ) and 1 . The structural studies of 4, 5 , and 11 prepared were carried out by nmr experiments in some details.