DABCO-mediated [4 + 4]-domino annulation reactions of ynones and α-cyano-α,β-unsaturated ketones: Mechanisms and the role of DABCO

Abstract

As natural products with important biological activities, eight-membered cyclic ethers can be achieved in good yields by the [4 + 4] domino annulation reactions of ynones and α-cyano-α,β-unsaturated ketones mediated by DABCO under mild conditions. To figure out the detailed reaction mechanism, quantum mechanical calculations were carried out. The global and local reactivity indexes were employed to evaluate the nucleophilic or electrophilic property and reactivity tendency of possible reaction sites in the reactants. Quantum theory of atoms in molecules were used to illustrate the intermolecular interactions formed in the complexes and transition states. The results indicate that two possible pathways exist for the [4 + 4] domino annulation reaction, and they were compared to figure out which one is more feasible and favorable. The important role of DABCO in the reaction was illustrated.