I2-Catalyzed Multicomponent Reactions for Accessing Densely Functionalized Pyrazolo[1,5-a]pyrimidines and Their Disulphenylated Derivatives
2016
Sun, Jun | Qiu, Jiang-Kai | Jiang, Bo | Hao, Wen-Juan | Guo, Cheng | Tu, Shu-Jiang
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.
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