Dual Role of Aryl Iodide in Cascade C–H Arylation/Amination: Arylation Reagent and Cocatalyst for C–N Formation

A cascade
C–H arylation/amination protocol using homoallylic
primary amines as the starting materials in the presence of a palladium
catalyst produces 2-aryl-1-pyrrolines with excellent regioselectivity
and in good yields. Mechanistic studies indicate that this transformation
proceeds via palladium-catalyzed Heck coupling, C–H amination,
and tautomerization. As an unprecedented example of aryl iodide acting
as an arylation reagent and a cocatalyst, the key role of aryl iodide
as a cocatalyst is to generate the active bivalent aryl palladium
catalyst to promote C–N formation during the C–H amination
step.