From starting material 2,3-dihydro-3-oxobenzo[c]-α-pyran (1), 3-acetyl-2,3-dihydro-3-oxobenzo- [c]-α-pyran (2) was obtained via condensation of α'-hydrogen of 1 with the ethoxy of ethyl acetate in the presence of sodium hydride. This β-diketone condensed with urea, thiourea or amidine derivatives to form 5,6-dihydro-5-oxa-1,3-penanthroline derivatives 3 and 4, respectively. The condensation of 1 with diethyl oxalate in the same condition afforded 3-ethoxyoxalyl-2,3-dihydro-3-oxobenzo[c]-α-pyran (5). 2-Aminoimidazole, 3-aminopyrazole, 3-aminotriazole, 2-aminobenzoimidazole and 3,5-diamino-4- phenylazopyrazole were condensed with β-ketoester 5 to generate 5,6-dihydro-5-oxa-1,3-penanthrolinoe further fused derivatives 6～10, respectively. The structures of all these compounds were characterized by elemental analysis, IR and ¹H NMR spectra.

Key words: heterocyclic synthesis, 5,6-dihydro-5-oxa-1,3-phenanthrolinopyrimidine, condensation reaction, 2,3-dihydro-3-oxobenzo(c)pyran