The Diels-Alder Chemoselectivity of 3,4,6,7-Tetramethylidenebicyclo(3. 2.1)octane-2-exo,8-syn-diyl Derivatives.

Strong dienophiles prefer to add onto the diene moiety attached at C(2),C(3) of 2,3,6,7-tetramethylidenebicyclo[3,2,1]octane ((+/-)-1; see Scheme 1), whereas in the case of 3,4,6,7-tetramethylidenebicyclo[3.2.1]octane-2-exo,8-syn-diyl derivatives. the diene moiety at C(6),C(7) reacts faster than that at C(3),C(4), as long the bulk of the 8-syn-substituent is large enough (see Schemes 2 and 3).