Mechanism and Origins of Selectivity in the Supramolecular [Ga4L6]12--Catalyzed Aza-Prins Reaction: The Mechanistic Studies

The mechanism, reactivity, and selectivityof the aza-Prins reactionin both the bulk solution and under [Ga4L6](12-) (L = N,N-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene)supramolecular catalysis were studied by means of theoretical calculations.In bulk solution, the steric effect and donor-acceptor interactionwhich favor the parallel-conformation transition state, in the selectivity-determiningcyclization step, account for the observed chemoselectivity that leadsto the alcohol product. While under the [Ga4L6](12-) catalysis, the host-guest noncovalentinteraction and confinement effect are more critical and make thevertical-conformation transition state more favorable, i.e., switchthe chemoselectivity of the reaction that leads to the piperidineproduct. The presented calculations explain the reactivities of substratesby the cavity size-determined guest recognition. The computationalfindings are in good agreement with experiment. This work sheds lighton development of more efficient and selective supramolecular catalysis.