Interactions beyond H-bonding: unveiling the role of unorthodox noncovalent interactions in charged thiourea and its catalytic efficiency

Abstract

The development of a catalyst with a rapid turnover rate under ambient reaction conditions is highly desirable. Inspired by biocatalytic systems, the field of charge-driven catalysis provides useful guidelines for designing efficient catalysts. The strategic integration of different non-covalent interactions into a 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 a σ-hole and H-bond. The incorporation of charge over the thione functionality alters the conformation of H-bonds (E,Z; whereas it mostly exists 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, resulting in good to excellent conversions at room temperature with the advantage of scalability. The charged catalyst exhibited multifold rate acceleration (5–40 min reaction time) compared to its neutral counterparts (>1 day). Kinetic studies, control experiments, computational analysis and mechanistic investigations support this remarkable catalytic activity.