Palladium‐Catalyzed Cycloisomerizations of Diarylacetylenes: Synthesis, Structures, and Physical Properties of Highly Substituted Naphthalenes and 8,8 a‐Dihydrocyclopenta[a]indenes

Abstract

Depending on the electronic properties of their substituents, the major products generated by palladium-catalyzed cycloisomerizations of diarylalkynes are either highly substituted 8,8a-dihydrocyclopenta[a]indenes 3 or naphthalenes 4. The structures of these compounds were verified by X-ray crystallographic analysis. Many functional groups tolerated the reaction conditions evaluated in this study. The isotope-labeled experiments indicated that added water has a critical role in forming both classes of compounds. The photophysical and electrochemical properties of cycloadducts 3 and their analogues were systematically studied and compared with computational predictions based on density functional theory. Dihydrocyclopenta[a]indenes 3 in either solid or liquid form display strong luminescence, whereas cyclopenta[a]indene 11 j is practically nonfluorescent. The functional groups directly attached to the backbone of compound 3 significantly influenced physical properties. The steric effect arising from the aryl substituents caused different luminescence phenomena, including aggregation-induced and -enhanced emission.

Intermolecular Desymmetrizing Gold‐Catalyzed Yne–Yne Reaction of Push–Pull Diarylalkynes

“…In addition diarylalkynes are known to dimerize to azulene derivatives in the presence of Pd, but yields are generally low, and high loadings or even stoichiometric amounts of metal are necessary . In the presence of stoichiometric amounts of oxidant and Cu as additive, some substrates form naphthalenes in the presence of Pd catalysts, but under these conditions, mainly 8,8‐α‐dihydrocyclopenta[a]indenes are obtained . Gold catalysts are known to dimerize non‐terminal ynamides, which gives rise to cyclopentadiene derivatives in most cases …”

Dinaphthozethrene and Diindenozethrene: Synthesis, Structural Analysis, and Properties

“…The longest absorption bands, λ abs , attributable to HOMO–LUMO transitions (S 0 → S 1 bands) of 3 - n Bu and 5 were determined to be 500 and 650 nm, respectively (see Supporting Information). The extremely low fluorescence of 5 should not be caused by the symmetry-forbidden HOMO-to-LUMO transition because its values of the measured absorption coefficient and the calculated oscillator strength ( f = 0.34) cannot be ignored.…”