Synthesis of H-Pyrazolo[5,1-a]isoquinolines via Copper(II)-Catalyzed Oxidation of an Aliphatic C−H Bond of Tertiary Amine in Air

A multicomponent reaction of 2-alkynylbenzaldehyde, sulfonohydrazide, and tertiary amine is discovered, which generates the unexpected H-pyrazolo[5,1-a]isoquinolines in good yields under mild conditions. In the reaction process, silver(I)-catalyzed intramolecular cyclization and copper(II)-catalyzed oxidation of an aliphatic C−H bond of tertiary amine in air are involved.