Nickel‐Catalyzed Tandem Knoevenagel Condensation and Intramolecular Direct Arylation: Synthesis of Pyrazolo[5,1‐a]‐isoquinoline Derivatives

A simple and efficient method for the synthesis of pyrazolo[5,1‐a]isoquinoline derivatives has been developed using the nickel‐catalyzed reaction of 1‐aryl‐2‐(1H‐pyrazol‐1‐yl)ethan‐1‐ones and 2‐bromo aldehydes. The overall transformation involves tandem Knoevenagel condensation and intramolecular direct arylation via activation of the C5−H bond of the pyrazole ring. A series of 27 drug‐like aroyl−substituted pyrazolo[5,1‐a]isoquinolines has been synthesized in moderate to good yields.