Regioselective Synthesis of6H -Pyrano[3,2-d ]pyrimidine-2,4(1H )-diones andFuro[3,2-d ]pyrimidine-2,4(1H )-diones

Abstract

A number of1,3-dimethyl-6H -pyrano[3,2-d ]pyrimidine-2,4(1H )-diones (4a–d) and1,3-dimethylfuro[3,2-d ]pyrimidine-2,4(1H )-diones (5a–c) have been regioselectively synthesised in88–94% and 80–90% yields respectively from thethermal [3s,3s] sigmatropic rearrangement of1,3-dimethyl-5-(prop-2-ynyloxy)uracils (3a–d).