A number of arynes, generated by treatment of haloarenes with sodium or potassium amide in tetrahydrofuran, were trapped with furan. The resulting dihydro epoxy arenes were converted into the following annulated isobenzofuran derivatives by using reverse Diels-Alder methodology: naphtho[l,2-clfuran, phenanthro[9,10-elfuran, pyreno[l,2-elfuran, pyreno[3,4- elfuran, anthra[l,2- elfuran, phenanthro[l,2- clfuran and phenanthro[3,4- elfuran. Bimolecular rate constants for the addition of maleic anhydride to these furans were measured, and were correlated with the Herndon structure count. Addition of arynes to selected members of this furan series yielded adducts which were deoxygenated to afford polycyclic aromatic hydrocarbons.

Elecanacin, an unusual cyclobuta-fused naphthalene-1,4-dione derivative isolated from the bulbs of Eleutherine Americana Merr. et Heyne (Iridaceae) has been obtained, together with its epimer isoelecanacin, by a 2 + 2 cycloaddition resulting from irradiation of 5-methoxy-2-(2-vinyloxypropyl)naphthalene-1,4-dione. The synthesis of enantiopure elecanacin starting with (R)-propylene oxide has established the absolute configuration of the natural product and has revealed that the sample isolated from the bulbs possessed an enantiomeric excess of only 14%.

5-Hydroxy-3-methylnaphtho[2,3-c]furan-4,9-dione (1), a metabolite isolated from Aloe ferox and Bulbine capitata, has been synthesized by a sequence involving an annulation reaction between the anion of 4-methoxy-3-oxo-1,3-dihydroisobenzofuran-1-carbonitrile (8) and (E)-pent-3-en-2-one, followed by subsequent construction of the furan ring through allylic bromination, hydrolysis, and dehydration as the key steps. The formation of several unusual products observed in annulation reactions between (8) and O-protected derivatives of (E)-5-hydroxypent-3-en-2-one (9) can be rationalized by invoking the intermediacy of a reactive o-quinone methide. 5,8-Dihydroxy-1-methylnaphtho[2,3-c]furan-4,9-dione (2), another naturally occurring naphtho[2,3-c]furan-4,9-dione, has been prepared by a Friedel–Crafts acylation of 1,4-dimethoxybenzene with 2-methylfuran-3,4-dicarbonyl dichloride. Arguments are presented that 5,8-dihydroxynaphtho[2,3-c]furan-4,9-dione is a better structural representation than the alternative 4,9-dihydroxynaphtho[2,3-c]furan-5,8-dione tautomer in such systems, as the latter would contain a reactive isobenzofuran moiety.

Reaction of benzonorbornadiene, 7-isopropylidenebenzonorbornadiene (1,4-dihydro-9-isopropylidene-1,4-methanonaphthalene) and 1,4-dihydro-1,4-epoxynaphthalene (7-oxabenzonorbornadiene) with dicarbonyldinitrosyliron, Fe(CO)2(NO)2, gave in good yields the corresponding dimers having the exo-trans-exo configuration. Treatment of a mixture of benzonorbornadiene and norbornadiene with Fe(CO)2(NO)2 gave a 'crossed dimer', in addition to the dimers derived from benzonorbornadiene and norbornadiene. The reaction of benzonorbornadiene with pentacarbonyliron at 100� gave the exo-trans-exo dimer and a ketone derived by dimerization and carbonyl insertion. This ketone, and the analogous ketone obtained from 7-isopropylidenebenzonorbornadiene, have been assigned the exo-trans-exo configuration. Reaction of 1,4-dihydro-1,4-epoxynaphthalene with enneacarbonyldiiron, Fe2(CO)9, at room temperature gave tetracarbonyl(l,4-dihydro-l,4-epoxynaphthalene)iron(0), in which the olefinic ח-bond is bonded to the metal. In solution at 63� this complex gave naphthalene.

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