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.