Zipper-mode double C-H activation: palladium-catalyzed direct construction of highly-fused heterocyclic systems

Direct construction of fused aromatic ring systems by "zipper-mode" double C-H bond activation is described. Treatment of (Z)-3-bromo-N-(2-bromo-3-phenylprop-2-enyl)aniline derivatives with a catalytic amount of Pd(OAc)2 and PCy3.HBF4 in the presence of Cs2CO3 in dioxane affords 4,5-naphtho[3,2,1-cd]indole derivatives in good yields. Introduction of heterocycles such as benzofuran, benzothiophene, or indole moieties into the substrates leads to the efficient construction of highly fused heterocyclic aromatic ring systems via C-H bond activation of the heteroaromatic rings.