Synthesis of Sulfonamides in the Biobased Solvent Cyrene.

A versatile protocol for the synthesis of sulfonamides using the biobased solvent Cyrene as reaction medium is reported. A wide range of primary and secondary amines were successfully employed, demonstrating the broad applicability of the method. The reactions proceed at room temperature and typically reach completion within 30-60 min. The resulting 20 sulfonamide products were isolated in good to high yields (up to 90%) by simple precipitation, upon addition of cold water and mild acid, without the need for chromatographic separation. The identified procedure offers an improved environmental profile, while maintaining high efficiency. Cyrene can be recovered and reused without loss of efficiency: Through a two-step extraction and filtration process, up to 79% of the solvent was successfully recovered and reused in a subsequent reaction cycle, furnishing the product in a yield comparable to that of the first cycle. Overall, this methodology provides a practical, mild, scalable, and more sustainable approach to sulfonamide synthesis.