Diels-Alder additions of hexachlorocyclopentadiene to some 7-substituted norbornadienes

Abstract

In contrast to the normal addition mode of hexachlorocyclopentadiene (3) to norbornadiene, which yields mainly (but not exclusively) aldrin having the endo-exo-1,4:5,8-dimethanonaphthalene skeleton, the reaction of (3) with norbornadien-7-yl acetate gives three adducts: 1,2,3,4,10,10-hexachloro-1,4,4a,5,8,8a-hexahydro-endo-endo-1,4:5,8-dimethanonaphthalen-syn-9-yl and -anti-9-yl acetates [(7) and (9)] and the 'normal' 1,2,3,4,10,10-hexachloro-1,4,4a,5,8,8a-hexahydro-endo-exo-1,4:5,8-dimethanonaphthalen-syn-9-yl acetate (11). The addition of (3) to 7-t-butoxynorbornadiene yields mainly the anti-9-t-butoxy-endo-endo adduct, analogous to (9), while the addition of (3) to 7-methylnorbornadiene gives mainly syn-9-methyl-endo-exo-adduct,analogous to (11). The structure of these adducts has been determined by spectroscopic (N.M.R. and infrared) and chemical (photochemicalcyclization of the endo-endo systems) means.