Pd-Catalyzed Indolization/peri-C-H Annulation/N-Dealkylation Cascade to Cyclopenta-Fused Acenaphtho[1,2-b]indole Scaffold.

A novel Pd-catalyzed cascade reaction of N,N-dialkyl-substituted o-alkynylanilines involving an indolization/peri-C-H annulation/N-dealkylation sequence has been developed to construct a cyclopenta-fused acenaphtho[1,2-b]indole (ANI) scaffold. A variety of aromatic hydrocarbons having a peri-C-H bond at the alkynyl terminus, such as naphthalene, phenanthrene, pyrene, and fluoranthene, were employed, affording the corresponding π-extended ANI derivatives. The ANI molecules showed relatively narrow energy gaps by increasing HOMOs and lowering LUMOs, implying their potential applications as π-segments in low-band-gap materials.