I2‑Catalyzed Multicomponent Reactions for Accessing Densely Functionalized Pyrazolo­[1,5‑a]­pyrimidines and Their Disulphenylated Derivatives

New I2-catalyzed multicomponent bicyclization reactions of β-ketonitriles with sulfonyl hydrazides have been established, providing a direct and metal-free access toward unreported pyrazolo­[1,5-a]­pyrimidin-4-ium sulfonates. The latter could be quantitatively converted into densely functionalized pyrazolo­[1,5-a]­pyrimidines in the presence of bases. Using sulfonyl hydrazides as a sulfenylating agent, the resulting pyrazolo­[1,5-a]­pyrimidines enabled I2-catalyzed unprecedented disulphenylations to access fully substituted pyrazolo­[1,5-a]­pyrimidines through direct C­(sp2)–H bond bifunctionalization.