Three-Component Fusion to Pyrazolo[5,1- a ]isoquinolines via Rh-Catalyzed Multiple Order Transformation of Enaminones.

A facile and practical method for the synthesis of fused tricyclic pyrazolo[5,1- a ]isoquinolines has been realized via the reactions of enaminones, hydrazine hydrochloride, and internal alkynes. By means of Rh catalysis, the extraordinary high-order bond functionalization, including the transformation of aryl C-H, ketone C═O, and alkenyl C-N bonds in the enaminones, marks the major feature of the cascade reactions. The results disclose the individual advantage of enaminones in the design of novel and efficient synthetic methods.