Supramolecular catalysis in the methylation of meta-phenylene ethynylene foldamer containing N,N-dimethylaminopyridine

Abstract

Density functional theory calculations were performed to elucidate the mechanism of the methylation reaction of the N,N-dimethylaminopyridine (DMAP)-modified meta-phenylene ethynylene foldamer with eight methyl sulfonate esters with different alkyl groups. The helical structure of the DMAP-modified mPE foldamer results from multiple intramolecular π–π stacking interactions between m-phenylene ethynylene arms, which can be characterized by the helical energy. The noncovalent interactions between the foldamer and the substrate can stabilize the transition state and result in an acceleration of the methylation reaction of the foldamer. Due to the different shapes of the alkyl chains of the methylating agents, the methylation rates of the foldamers with linear and branched substrates show different rules. It is expected that these mechanistic insights into supramolecular catalysis can be used in the design and preparation of supramolecular catalysts and reactors.