TfOH Catalyzed [3+2] Cycloaddition of Cyclopropane 1,1‐Diesters with Nitriles: A Density Functional Study

Abstract

The mechanistic pathways for TfOH catalyzed [3+2] cycloaddition reaction between cyclopropane 1, 1 diesters and MeCN has been investigated using density functional theory. The study sheds light on selective synthesis of 1‐pyrroline or γ‐lactone derivatives in two different reaction conditions. Analysis of global reactivity descriptors in the solvent free medium predicts the protonated cyclopropane 1,1 diesters and MeCN as strong electrophile and nucleophile respectively, favoring intermolecular reaction to give 1‐pyrroline derivative as the product. On the other hand, the presence of solvent environment with DCM solvent significantly supresses this nature of the two molecules to undergo intermolecular reaction. Protonated cyclopropane 1,1 diester, therefore, prefers intramolecular rearrangement to yield γ‐lactone. While the synthesis of 1‐pyrroline derivative follows pathway involving a transition state showing weak interaction between two reactants, γ‐lactone synthesis undergo mechanism preferring initial cyclopropane ring opening transition state. Molecular electron density topography yield support to the proposed mechanism.