One-Pot Synthesis Of 5h-Chromeno[3,4-B]Pyrazin-5-One Derivatives From 4-Amino-3-Nitrocoumarin And Alpha-Dicarbonyl Compounds

2,3-Disubstituted [3,4]-fused pyrazinocoumarins have been synthesized in very good yields by the one-pot reaction of 4-amino-3-nitrocoumarin with alpha-dicarbonyl compounds in the presence of PPh3 in n-pentanol under microwave irradiation. The reactions of 3,4-diaminocoumarin with alpha-dicarbonyl compounds in o-xylene under microwaves led also to the title compounds in excellent total yields.[GRAPHICS].