Treatment of 6-(N-alkylanilino)-2-phenylpyrimidin-4 (3H)-ones, which were prepared by the condensation of 6-chloro-2-phenylpyrimidin-4 (3H)-one with N-alkylanilines, with the Vilsmeier reagent (dimethylformamide-phosphoryl chloride) gave the corresponding 10-alkyl-2-deoxo-2-phenyl-5-deazaflavins (III) in excellent yields. Heating of 6-chloro-5-formyl-3-phenyluracil with N-alkylanilines in dimethylformamide gave the corresponding 10-alkyl-3-phenyl-5-deazaflavins (VI) in a single step. The abilities of the 5-deazaflavins (III) and (VI) thus obtained to oxidize benzyl alcohol and benzylamine were compared, and some automatic recycling of the oxidation reactions was observed. The reaction of compounds III with benzylamine exceptionally gave the adducts, 5-benzylamino-2-deoxo-2-phenyl-5-deazaflavins.