N‐ethoxycarbonylamidines as starting materials and intermediates in the synthesis of heterocyclic compounds

Treatment of N‐ethoxycarbonylthioamides (1) with primary aromatic amines yields N‐aryl‐N′‐ethoxy‐carbonylamidines (2), which thermally cyclize to 2‐aryl‐4(3H)‐quinazolinones (6). Analogous reactions of 1 with ethyl 3‐aminocrotonate and with 2‐amino‐2‐thiazoline lead respectively to ethyl 2‐aryl‐3,4‐dihydro‐6‐methyl‐4‐oxo‐5‐pyrimidinecarboxylates (10) and to 2‐aryl‐6,7‐dihydro‐4H‐thiazolo[3,2‐a]‐1,3,5‐triazin‐4‐ones (14), presumably through the corresponding N‐ethoxycarbonylamidines.