Pd‐Catalyzed Annulation of 1‐Halo‐8‐arylnaphthalenes and Alkynes Leading to Heptagon‐Embedded Aromatic Systems

A palladium‐catalyzed heptagon‐forming annulation reaction between 1‐halo‐8‐arylnaphthalene and diarylacetylene is reported. The reaction is promoted using a catalytic system comprised of Pd(OAc)2, moderately electron‐deficient triarylphosphine P(4‐ClC6H4)3, and Ag2CO3 to afford benzo[4,5]cyclohepta[1,2,3‐de]naphthalene derivatives in moderate to good yields, in preference to fluoranthene as a competing byproduct. Twofold annulation can also be achieved to access a novel heptagon‐embedded polycyclic aromatic hydrocarbon compound. Polycyclic aromatic hydrocarbons: A palladium‐catalyzed annulation reaction between 1‐halo‐8‐arylnaphthalene and diarylalkyne is reported. Using a moderately electron‐poor triarylphosphine, the reaction takes place in preference to fluoranthene formation, affording benzo[4,5]cyclohepta[1,2,3‐de]naphthalene derivatives in moderate to good yields. Twofold annulation is also achieved to access a novel heptagon‐embedded polycyclic aromatic hydrocarbon (see scheme).