Reactions of cyclo-octatetraene and its derivatives. Part III. Cycloocta-1,3,5-triene as a dienophile

Abstract

Cyclo-octa-1,3,5-triene reacts via its valence tautomer bicyclo[4,2,0]octa-2,4-diene with hexachlorocyclopentadiene and with tetrachlorocyclopentadienone acetals to afford adducts which are tetracyclo[8,2,1,O^2,9,O^5,8]trideca-3,11-dienes (II). Similar reactions take place with tetraphenyl- and 2,5-dimethyl-3,4-diphenyl-cyclopentadienone, although the initial (4 + 2)π cycloaddition is followed by Cope rearrangement to give tetracyclo[5,4,2,O^2,6,O^8,11]-trideca-4,12-dien-3-ones (III); however, the formation of co-products which are hexa-1,3-dienylbenzenes (V) indicates that some direct addition to the eight-membered ring also occurs.