Synthesis of 5‐substituted uracils and 2,4‐dimethoxypyrimidines by wittig olefination

A variety of new 5‐alkenyluracils has been prepared in high yields by Wittig olefination of 5‐formyl‐1‐octy‐luracil, 5‐formyl‐1,3‐dioctyluracil and 5‐formyl‐2,4‐dimethoxy pyrimidine with stabilized and semistabi‐lized phosphorus ylides. The conformation of the products is discussed on the basis of ¹H NMR spectral data.