A SIMPLE APPROACH TOWARDS THE SYNTHESIS OF OXADEAZAFLAVINES

The synthesis of oxadeazaflavine (2H-chromeno[2,3-d]pyrimidine-2,4(3H)-dione) derivatives (1a, 1b and 1c) from barbituric acid and salicylaldehydes as starting materials was shown to be possible using water as solvent at room temperature. The orange intermediate formed, an anthocyanidin-like precursor of the desired products, gave reasonable yields of the oxadeazaflavines when treated with acetic acid-acetic anhydride mixture. When the reaction was carried out at 100-degrees-C the corresponding 1,5-dihydro-5(5'-barbituryl)-2H-chromeno[2,3-d]pyrimidine-2,4(3H)-diones (4a, 4b and 4c) were obtained. The reaction of barbituric acid with nitrosalicylaldehydes, at either 25 or 100-degrees-C, leads only to the corresponding arylidenebarbituric acids.