Post-Formation of Fused Pentagonal Structure on Fjord Region of Polyaromatic Hydrocarbons under Hydrothermal Conditions

This study explores the synthesis of cyclopenta-fused polyaromatic hydrocarbons (CP-PAHs) via Pt-catalyzed cyclization in water, focusing on the formation of fused pentagonal rings within heavily fused PAH frameworks. Utilizing platinum catalysts at lower temperatures (200-260 °C) in water, led to the successful synthesis of singly cyclized CP-PAHs. The reaction conditions facilitated the mono-cyclization of substrates such as dibenzo[g,p]chrysene and its isomers, yielding the desired products while suppressing the formation of bis-cyclized compounds. The use of Fe2O3 as an additive in conjunction with PtO2 was effective to suppress hydrogenation of the substrates and products. The products exhibited a redshift in UV-visible absorption and photoluminescence bands due to a decrease in the HOMO-LUMO energy gap. These findings highlight the potential of Pt-catalyzed cyclization for the controlled synthesis of CP-PAHs, with implications for various applications in materials science.

Acenaphthenoannulation Induced by the Dual Lewis Acidity of Alumina

We have discovered a dual (i. e., soft and hard) Lewis acidity of alumina that enables rapid one‐pot π‐extension through the activation of terminal alkynes followed by C−F activation. The tandem reaction introduces an acenaphthene fragment – an essential moiety of geodesic polyarenes. This reaction provides quick access to elusive non‐alternant polyarenes such as π‐extended buckybowls and helicenes through three‐point annulation of the 1‐(2‐ethynyl‐6‐fluorophenyl)naphthalene moiety. The versatility of the developed method was demonstrated by the synthesis of unprecedented structural fragments of elusive geodesic graphene nanoribbons.

Multiple [n]helicenes with various aromatic cores

Usually, multiple [n]helicene molecules have a characteristic aromatic core, such as benzene, naphthalene, pyrene, perylene, hexabenzocoronene, corannulene, or azacorannulene.

Unusual Fusion of α-Fluorinated Benzophenones under McMurry Reaction Conditions

By exposure of α-fluorinated benzophenones to McMurry reaction conditions, we have observed the remarkable formation of 9,10-diphenylanthracene derivatives. This unexpected transformation necessitates the cleavage of the exceptionally stable aromatic C-F bond under mild McMurry conditions. In this work, the condensation of several related fluorinated benzo- and acetophenones has been investigated, which allow us to propose a domino-like fusion mechanism for this unusual transformation. The scope and limitations of the fluorine-promoted benzophenone fusion are subsequently discussed.

Synthetic and structural considerations on highly curved bowl-shaped fragments of fullerenes

Numerous highly curved fragments of C60 and unique subunits of C70 were synthesized under mild conditions using metal-catalyzed protocols. According to X-ray crystallographic analyses, highly curved fragments of C60 have a maximum π-orbital axis vector (POAV) pyramidalization angle of up to 12.9 °, whereas distinctive fragments of C70, analogous to the tube portion of the rugby-shaped buckyball, are less curved. Among the eight buckybowls studied herein, five form polar crystals. Depending on the molecular geometry, the inversion dynamics of buckybowls involves either a planar or an S-shaped (non-planar) transition structure.

Metal-catalyzed annulation reactions for π-conjugated polycycles

The progress of the metal-catalyzed annulation reactions toward construction of various π-conjugated polycyclic cores with high conjugation extension is described. This article gives a brief overview of various annulation reactions promoted by metal catalysts including C-H bond functionalization, [2+2+2] cycloaddition, cascade processes, ring closing metathesis, electrophilic aromatization, and various cross-coupling reactions. A variety of conjugated polycycles with planar, bowl-shaped, and helical structures have been constructed in high efficiency and selectivity.