Palladium‐Catalyzed Direct C(sp 3 )−H Arylation of 5 H ‐Imidazo[2,1‐ a ]isoindole Scaffolds With Arylbromides

The study of Pd(0)‐catalyzed C−H bond arylation of methyl 5 H‐ imidazo[2,1‐ a ]isoindole‐3‐carboxylates with aryl bromides is reported. This methodology gives ready access to a wide range of methyl 5 H ‐imidazo[2,1‐ a ]isoindole‐3‐carboxylates that are monoarylated at their benzylic sites. The C(sp 3 )−H bond arylation methodology is driven by regioselectivity under weakly basic conditions avoiding remarkably side C(sp 2 )−H poly‐arylation of the (hetero)aromatic unit. The process was applied to the preparation of novel imidazo[2,1‐ a ]isoindole‐based neurotransmitter Neuropeptide S antagonist analog.