Suzuki–Miyaura coupling of aryl fluorosulfates in water: a modified approach for the synthesis of novel coumarin derivatives under mild conditions

We herein report a modified, eco-friendly and atom-economical approach for the synthesis of a series of novel coumarin analogues via Suzuki–Miyaura cross-coupling methodology under mild conditions. The utilization of coumarin fluorosulfate as an atom-economical pseudohalide based electrophilic coupling partner was the key for success of our modified methodology. In addition, the use of water as a solvent, exceptionally milder reaction conditions and traditional catalytic systems further demonstrates the synthetic utility of the developed protocol. A comparative study of different pseudohalide leaving groups has been carried out in the later stage to understand the efficiency of aryl fluorosulfate. From this study, the increased hydrophilic nature of the fluorosulfate electrophilic coupling partner when compared to the other electrophiles has been realized. This allowed the increased solubility of the fluorosulfate electrophile in water under milder temperature conditions thereby furnishing the desired products in good to excellent yields.