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-thiazolo3,2-a]-1,3,5-triazin-4-ones ( 14 ), presumably through the corresponding N-ethoxycarbonylamidines.