Silver-Catalyzed Synthesis of 5-Amino-4-sulfonyl Pyrazoles from 1,2-Diaza-1,3-dienes.

A facile and dependable synthetic route for 5-amino-4-sulfonyl pyrazoles, which are substantially important in pharmaceuticals, is highly desirable. This work presents a novel cascade reaction for their efficient synthesis. The approach utilizes silver as a catalyst for C(sp)-H sulfonylation of readily available starting materials 1,2-diaza-1,3-dienes with sulfinate salts, followed by intramolecular cascade cyclization annulation to afford the desired 5-amino-4-sulfonyl pyrazoles in good to excellent yields under mild conditions.