SYNTHESIS, -SIGMATROPIC REARRANGEMENT AND ELECTROPHILIC BEHAVIOR OF ANGULARLY ALKYLATED 2-CARBETHOXY-TRICYCLO2,6>DECADIENONES

Article abstract of DOI:10.1016/S0040-4020(01)86425-5

The angular alkylation of tricyclodecadienone ester 1 with alkyl halides is described.A considerably diminished thermal stability is observed for the angularly alkylated tricyclic esters 7.Even at ambient temperature they rapidly undergo an unusually facile Cope rearrangement to bridge ketones 8.Both steric and electronic effects are held responsible for this unique behavior of 7.In contrast to ester 1, 6-alkyl esters 7 do not generally undergo conjugate addition.Instead, bridge ketone addition products are formed which may arise either from initial 1,2-nucleophilic addition to the C5-ketone function in 7 followed by Cope rearrangement or from a stereoselective nucleophilic addition to the bridge ketone function in the Cope rearrangement compound 8.The remarkable stereoselectivity of the latter reaction is discussed in terms of Cieplak's model for the addition of nucleophiles to cyclic ketones.