Synthesis of Tetrahydro-2-furyl Derivatives of 5-Substituted Uracils

抄録

Addition of 5-fluorouracil (1) to the double bond of 2, 3-dihydrofuran (3) without using any catalyst progressed smoothly at an elevated temperature and afforded an equilibrium mixture of 1-(tetrahydro-2-furyl)-5-fluorouracil (5) and 1, 3-bis (tetrahydro-2-furyl)-5-fluorouracil (7). By choosing favourable reaction conditions, each of these compounds was obtained in high yield. Thermal decomposition of 7 gave an equimolar mixture of 3 and 5. At a higher temperature, 5 underwent thermal reaction to yield 1 and 3. Study of the present addition reaction was extended to other 5-substituted uracils (8, R=-H, -CH₃, -Cl, -Br, -COOCH₃, -CONH₂, -CN) which furnished the corresponding 1-(tetrahydro-2-furyl)-and 1, 3-bis (tetrahydro-2-furyl)-derivatives (9-15, 18-23) with high yields. A very small amount of 3-(tetrahydro-2-furyl)-5-substituted uracils (6, 16, 17) by-produced in the reactions was isolated and the structures unequivocally identified.