Synthesis of dicyclopenta[ef,kl]heptalene (azupyrene). II. Routes from 1,6,7,8,9,9a-hexahydro-2H-benzo[c,d]azulen-6-one and 5-phenylpentanoic acid

Abstract

In the second phase of the synthesis of azupyrene, two routes via the intermediate 1, 5,6,6a, 7,8,9a-heptahydro-2ff-indeno[5,4,3-cde]azulene (7) have béen investigated: (i) from l,6,7,8,9,9a-hexahydro-2ff-benzo[c,<f]azulen-6-one (1) as depicted in Schemes I, II, and III, and (ii) from 5-phenylpeptanoic acid (23) as depicted in Scheme IV. The best route afforded 7 as the cis isomer (19) in ca. 43% overall yield from 1 and involved just three operational steps. This provided a seven-step synthesis of 19 from indené in 8-9% overall yield. Reaction of

The road to bis‐periazulene (cyclohepta[def]fluorene): Realizing one of the long‐standing dreams in nonalternant hydrocarbons

“…[88] Starting from 1-indanone, the key hydrocarbon 48 was prepared in several steps. [89] The conversion of 48 into 40 was conducted in three steps, including (i) ring expansion with ethyl diazoacetate, (ii) hydrolysis, and (ii) decarboxylation/dehydrogenation using Pd/C in methyl oleate at 350 C. [90] Despite the low yield of 40 in 2.5%, the same group deeply characterized the magnetic and electronic [88] (C) Jutz and Schweiger's improved synthetic routes to 40. [91,92] (D) Observed bond lengths (Å) of 40.…”

“…[ 89 ] The conversion of 48 into 40 was conducted in three steps, including (i) ring expansion with ethyl diazoacetate, (ii) hydrolysis, and (ii) decarboxylation/dehydrogenation using Pd/C in methyl oleate at 350°C. [ 90 ] Despite the low yield of 40 in 2.5%, the same group deeply characterized the magnetic and electronic structure of 40 by nuclear magnetic resonance (NMR), UV‐Vis, infrared (IR), and diamagnetic susceptibility measurements. [ 88 ] In later years, Jutz and Schweiger provided two simple synthetic routes to 40 [ 91,92 ] using modified manners of Ziegler–Hafner azulene synthesis (Figure 11C).…”

On-Surface Synthesis of Unsaturated Carbon Nanostructures with Regularly Fused Pentagon–Heptagon Pairs

“…In the hexagonal lattice of graphene, nanostructures of fused pentagon–heptagon pairs are found as defects at grain boundaries (see Figure a,b). − Numerous calculations have suggested that controlling these “defect” structures is essential for tuning the properties of graphene-based materials. ,− The unsaturated pentagon–heptagon bicyclic hydrocarbon, named azulene, is a classic of organic chemistry . Organic synthesis has also provided several polycyclic aromatic hydrocarbons (PAHs) containing two fused azulenes, which exhibit unique physical properties, including small optical energy gaps and open-shell biradical characters. − Nevertheless, the construction of sp 2 -carbon skeletons with multiple fused pentagon–heptagon pairs has remained challenging.…”

Extension of Non‐alternant Nanographenes Containing Nitrogen‐Doped Stone‐Thrower‐Wales Defects

“…[16][17][18] However, since Anderson and co-workers reported the first synthesis and characterization of azupyrene in 1968, the synthesis of π-expanded nanographenes containing azupyrene unit has remained elusive in recent decades, likely owing to the lack of a facile synthetic approach and ring rearrangement. [16,17,19] Consequently, the physicochemical properties induced by this topological S-T-W defect in graphene nanostructures are difficult to ascertain. Nevertheless, it is possible to induce unique physicochemical properties when integrating such non-alternant topologies in graphene molecules.…”

“…However, apart from these azulene or pentalene moieties, research on larger non‐alternant structures is rare due to the challenges of in‐solution synthesis. In the middle of the 19 th century, different types of non‐alternant molecules, such as azupyrene (the isomer of alternant pyrene, also called Stone–Thrower–Wales (S–T–W) defect in graphene, Figure 1a) and dicycloheptapentalene (also called the inverse S–T–W defect in graphene, Figure 1a), were synthesized [16–18] . However, since Anderson and co‐workers reported the first synthesis and characterization of azupyrene in 1968, the synthesis of π‐expanded nanographenes containing azupyrene unit has remained elusive in recent decades, likely owing to the lack of a facile synthetic approach and ring rearrangement [16,17,19] .…”