Unusual Reactions of 6‐Amino‐1,3‐dimethyluracil with Some Aliphatic Aldehydes.

6-Amino-1,3-dimethyluracil reacts with two molecules of alkanals (butanal or pentanal) in formic acid to give 1,3,7,9-tetramethyl- 2,4,6,8-tetraoxopyrido[2,3- d ][6,5- d’ ]dipyrimidine and the corresponding 3,4-dialkyl-substituted 6,8-dimethyl-5,7-dioxopyrido[2,3- d ]- pyrimidines.