Three-Component Chemo-Selective Synthesis of <i>N</i>-(<i>o</i>-Alkenylaryl) Pyrazoles by Pyrazole Annulation and Rh-Catalyzed Chemo-Selective Aryl C–H Addition Cascade

Abstract

By using readily available enaminones, aryl hydrazine hydrochlorides, and alkynes as starting materials, the chemo-selective three-component synthesis of atropisomeric N -( o -alkenylaryl) pyrazoles has been efficiently accessed with rhodium catalysis. Unlike Satoh–Miura reaction leading to the alkyne-based C–H benzannulation by using prior prepared N -phenyl pyrazoles and alkynes as substrates, this three-component protocol displays unprecedented selectivity of C–H alkenylation by blocking the second round metal alkenylation with the key protonation step in the presence of acids.