I₂-catalyzed multicomponent reactions for accessing densely functionalized pyrazolo[1,5-a]pyrimidines and their disulphenylated derivatives

Jun Sun,¹ Jiang-Kai Qiu,¹ Bo Jiang,* Wen-Juan Hao, Cheng Guo,* Shu-Jiang Tu,*

(1代表共同一作)

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.

J. Org. Chem. 2016,  81, 3321-3328