First Experimental and Theoretical Evidence of a Deactivating Enone Dienophile in the Transannular Diels−Alder Reaction

A thorough study of the transannular Diels−Alder (TADA) reaction of trans-trans-trans macrocyclic trienes was carried out. It led to a better understanding of various parameters that govern the TADA reaction in particular and the Diels−Alder reaction in general. Thus, carbonyl activation of the dienophile is thoroughly discussed in light of new experimental and theoretical data. An enone dienophile is found to deactivate the reaction, although it remains planar at the transition state. This unusual result was discussed in terms of tether substituents that provoke destabilization of the transition state.