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Showing papers on "Benzopyran published in 1968"


Journal ArticleDOI
TL;DR: In this paper, a pentacyclic ring system was obtained from 4-hydroxy-5-benzofuranyl ketones by demethyl-cyclization with pyridine hydrochloride, hydroiodic acid or aluminum chloride.
Abstract: 4-Hydroxyfuro[2′,3′:7,8]coumarin (16) and its 3-phenyl (10) and 3-(2-methoxyphenyl) (11) derivatives were prepared from the corresponding 4-hydroxy-5-benzofuranyl ketones (15, 8a and 8b) by the action of ethyl carbonate and sodium. The furocoumarin 11 thus obtained was converted to 5H-benzofuro[3,2-c]furo[2,3-h][1]benzopyran-5-one (18), a compound having a new pentacyclic ring system, by the demethyl-cyclization with pyridine hydrochloride, hydroiodic acid or aluminum chloride. The attempted preparation of these compounds through their dihydro compounds is also described; 2,3-dihydro-4-hydroxybenzofuran (1) was acylated with phenylacetic acid, with 2-methoxypheny lace tic acid or with 2,4,5-trimethoxyphenylacetic acid by the action of polyphosphoric acid to give a mixture of the 5- and 7-acylated compounds (3 and 2), and the formers were converted to the corresponding 4″,5″-dihydrofuro[2″,3″:7,8]isoflavones (6), 4″,5″-dihydro-2-methylfuro-[2″,3″:7,8]isoflavones (4) and 4′,5′-dihydro-4-hydroxyfuro[2′,3′:7,...

6 citations