Synthesis and reactions of some new allyl furobenzopyranone derivatives

Reaction of visnaginone 1 with allyl bromide gave O‐allyl visnaginone 2 which underwent Claisen rearrangement to yield 7‐allylbenzofuran derivative 3 . Reaction of 3 with different aromatic aldehydes gave the corresponding 5‐cinnamoylbenzofuran derivatives 4a‐d . Condensation of the latter chalcones 4a,c,d with hydrazine hydrate and phenylhydrazine provided, the corresponding pyrazoline derivatives 7a‐f . Claisen condensation of compound 3 with ethyl acetate and diethyl carbonate afforded Claisen adducts 8 and 12 which easily cyclized to 9 and 13 , which are endowed with interesting biological properties.