Merging C–H Activation and Alkene Difunctionalization at Room Temperature: A Palladium-Catalyzed Divergent Synthesis of Indoles and Indolines

A palladium-catalyzed
1,2-carboamination through C–H activation
at room temperature is reported for the synthesis of 2-arylindoles,
and indolines from readily available, inexpensive aryl ureas and vinyl
arenes. The reaction initiates with a urea-directed electrophilic
ortho palladation, alkene insertion, and β-hydride elimination
sequences to provide the Fujiwara–Moritani arylation product.
Subsequently, aza-Wacker cyclization, and β-hydride elimination
provide the 2-arylindoles in high yields. Intercepting the common
σ-alkyl-Pd intermediate, corresponding indolines are also achieved.
The indoline formation is attributed to the generation of stabilized,
cationic π-benzyl-Pd species to suppress β-hydride elimination.