Synthesis of some pyranobenzopyrans and 3-styryl 4H (1) benzopyran [3,4-d]isoxazoles

The chalcones of 4-hydroxycoumarins (IIa-h) are prepared from 3-acetyl-4-hy droxycoumarins via Claisen condensation with different aromatic aldehydes w hich on cyclization with 10% sulphuric acid in ethanol and selenium dioxide in amyl alcohol gave 4H, 5H-2,3-dihydro-2-phenyl pyrano [3,2-c] 1-benzopyr an-4,5-diones (IIIa-h) and 4H, 5H-2-phenyl pyrano-[3,2-c] 1-benzopyran-4,5- diones (IVa-h) respectively. Whereas oximes of chalcones (Va-h) on refluxin g with silica gel and dichloroethane give-2-oxo-3-styryl 4H-1-benzopyran [3 ,4-d] isoxazoles (Vla-h).