Reciprocity of CO⋯π interactions with the dominant anion–π on fullerene (C60)– amine-based organocatalysts: a mechanistic elucidation for addition vs. decarboxylation reaction

Abstract

Reiterating the counterintuitive anion–π interactions that J. López-Andarias and coworkers [J. Am. Chem. Soc., 2017, 139, 13296–13299] have experimentally discussed in their pioneering work, the current investigation explores the role of such interactions in the fullerene-amine conjugate-based organocatalysis reaction via density functional theory (DFT) protocols where the underlying catalytic reaction paths have been ascribed to unique transition state geometries. The reaction between MAHT (malonic acid half thioester) and nitrostyrene was reported to follow the addition and decarboxylation pathways. Our findings exclusively help to visualize and quantify anion–π interactions operating in the planar enolate intermediates. We substantiate that the synergistic effects of anion–π and CO⋯π surface interactions play a central role in distinguishing the planar and bent tautomers with delocalized and localized charges, respectively, on the π-acidic surfaces of fullerene C₆₀ catalysts. Overall, the theoretical pieces of evidence suggest a selective acceleration of the addition pathway, leading to a higher yield of the addition product, as observed in the experiments [J. Am. Chem. Soc., 2017, 139, 13296–13299].