Cyclisation of 3-cyclopent-2-enyl-4-hydroxy1benzopyran-2-one

摘要

3-Cyclopent-2-enyl-4-hydroxy1benzopyran-2-one 3 has been prepared by the reaction of 3-chlorocyclopent-2-ene 2 and 4-hydroxy1benzopyran-2-one 1. Compounds 3 or its acetate 4 on treatment with pyridine hydrotribromide in dichloromethane at 0-5deg C for 2 hr give fused furochromone 5 in 90 yield. Compound 5 on refluxing in 50 sulphuric acid undergoes rearrangement to furnish fused furo coumarin 7 in 87 yield.