An expedient method for the synthesis of 6-substituted uracils under microwave irradiation in a solvent-free medium

Condensation of malonic acid 1 and ureas 2a-f proceeds smoothly in the presence of acetic anhydride 3 under microwave irradiation in solvent-free conditions to give 6-hydroxy-uracils 4 in excellent yields. Under identical conditions, the condensation of cyanoacetic acid 5 and ureas 2a,b,g and h in the presence of acetic anhydride 3, followed by cyclization in the presence of sodium hydroxide affords 6-amino-uracils 6 in high yields. The work-up procedures are simple and products need no purification.