Highly condensed polycyclic systems. Part II. Pentacyclo[7,2,1,02,8,03,11,06,10]dodec-4-enes

Abstract

Hexachlorocyclopentadiene and tetrachlorocyclopentadienone acetals undergo thermal (4 + 2)π cycloadditions with cyclohepta-1,3,5-triene. The resulting endo-1 : 1-adducts contain a 1,3-diene system and an isolated doublebond; prolonged heating of these adducts effects intramolecular Diels–Alder addition of these structural features with the formation of pentacyclo[7,2,1,0^2,8,0^3,11,0^6,10]dodec-4-enes.

Bromination of the hexachlorocyclopentadiene–cycloheptatriene adduct involves selective attack on the 5,6-double bond and yields a cis-diequatorial dibromide.