Double CH Functionalization in Sequential Order: Direct Synthesis of Polycyclic Compounds by a Palladium‐Catalyzed CH Alkenylation–Arylation Cascade

Palladium‐catalyzed cascade CH alkenylation and arylation provides convenient access to polycyclic aromatic compounds. Treatment of 3‐bromoaniline derivatives bearing a bromocinnamyl group on the nitrogen atom with a catalytic amount of [Pd(OAc) 2 ] and PCy 3 ⋅HBF 4 in the presence of Cs 2 CO 3 in dioxane affords naphthalene‐fused indole derivatives in good yields. This double cyclization reaction is also applicable to heterocyclic substrates, giving fused indoles containing a heteroaromatic ring such as dibenzofuran, dibenzothiophene, carbazole, indole, or benzofuran through heterocyclic CH arylation. When using a 2,6‐unsubstituted aniline derivative, the first CH arylation preferentially proceeds at the more hindered position of the aniline ring.