Some Cycloaddition Reactions of 5,8-Dimethoxynaphtho[2,3-c]furan-4,9-dione

Abstract

Methylation of 5,8-dihydroxynaphtho[2,3-c]furan-4,9-dione (5) gave, in addition to the title ether (7), the fragmentation products 4-hydroxy-1,5,8-trimethoxy-3-methylnaphthalene-2-carbaldehyde (8) and its methyl ether (9). Addition of benzyne to (7) afforded mainly the expected [4+2] cycloadduct (15) and minor amounts of adduct (16), derived by addition of (7) to (15), and adduct (19), derived by a homo- or 1,3-addition of benzyne to (15), followed by decarbonylation. Adducts of (7) with 1,4-dihydro-1,4-epoxynaphthalene and dimethyl acetylenedicarboxylate also were prepared.