The Synthesis of [3,4-c]Furooctalene, [1,2:5,6]Di[c]furocyclooctatetraene, and I,2-Benzo[5,6-c]furocyclooctatetraene

Abstract

Oxidation of 1,2-bis(hydroxymethyl)cyclooctatetraene (3) with manganese dioxide gave cyclooctatetraene-1,2-dicarboxaldehyde (4), besides other products. Wittig reaction of 4 with furan-3,4-bis(methylenetriphenyl-phosphonium chloride) (9) and lithium ethoxide led to [3,4-c]furooctalene (10). The spectral properties of 10 show that the eight-membered rings are nonplanar and do not possess delocalized π electrons. Diels-Alder reaction of 10 with dimethyl fumarate yielded a monoadduct (12), derived by addition to the terminal eight-membered ring. Wittig reaction of furan-3,4-dicarboxaldehyde (13) with the furan salt 9 gave [1,2:5,6]di[c]furocyclooctatetraene (14). The related dimethyl [1,2:5,6]di[c]furocyclooctatetraene-3,8-dicarboxylate (16) was obtained by the reaction between 13 and furan-3,4-diacetic acid (15). Wittig reaction between ophthalaldehyde (19) and the furan salt 9 led to 1,2-benzo[5,6-c]furocyclooctatetraene (20), a substance which was also obtained by the reaction between furan-3,4-dicarboxaldehyde (13) and o-xylylenebis(triphenylphosphonium bromide) (7). Diels-Alder reaction of 14 and 20 with dimethyl fumarate gave adducts (18 and 21, respectively) derived by addition to the furan rings. Show more