Synthesis of pyrazolo[5,1-a]isoquinolines via silver(I)-rhodium(I) cooperative catalysis in the reaction of N'-(2-alkynylbenzylidene)hydrazide with cycloprop-2-ene-1,1-dicarboxylate.

A tandem reaction between N'-(2-alkynylbenzylidene)hydrazide and cycloprop-2-ene-1,1-dicarboxylate co-catalyzed by silver triflate and tris(triphenylphosphine)rhodium chloride is reported. The reaction proceeds through 6-endo-cyclization, [3 + 2] cycloaddition, cyclopropane opening, and aromatization, leading to pyrazolo[5,1-a]isoquinolines in moderate to good yields.