Interactions beyond H-bond: Unveiling the role of unorthodox non-covalent interactions in charged thiourea and its catalytic efficiency

Abstract

The development of catalyst with a rapid turnover rate under ambient reaction condition is highly desired. Inspired by the biocatalytic systems, the field of charge-driven catalysis provide useful guidelines for designing efficient catalysts. The strategic integration of different non-covalent interactions into the single catalytic system is an interesting phenomenon, that could be engaged effectively for diverse chemical reactions. On this front, here we report charged thioureas with a simple design perspective that offers a significant advantage in terms of catalytic activity by leveraging the unusual combination of σ-hole and H-bond. Incorporation of charge over the thione functionality alters the conformation of H-bonds (E, Z; whereas it mostly exist as Z, Z in thiourea systems), and additionally offers σ-hole interactions for the activation of substrates. The catalyst demonstrated potential activity towards three different classes of organic reactions and resulted good to excellent conversions under room temperature conditions with the advantage of scalability. The charged catalyst exhibited multifold rate acceleration (5 – 40 min) compared to its neutral counterparts (>1 day). Kinetic studies, control experiments, computational analysis and mechanistic investigations supports the remarkable catalytic activity.