Reaction of 1,3,4-thiadiazolo and 1,3,4-triazolo[3,2-c]quinazoline derivatives with active methylene compounds

Fused quinazoline derivatives 1 and 4 react with active methylene compounds and depending on the annelated five-membered ring, two types of transformations have been observed. The 1,3,4-thiadiazolo3,2-c]quinazoline 1 , underwent the five-membered ring opening reaction to afford the 3,4-dihydroquinazolines 2 in good yields, whereas the 1,3,4-triazolo3,2-c]quinazoline 4 underwent nucleophilic attack at 2-position of the quinazoline ring to yield the corresponding 1,2,4-triazoles 5 .