Ring Reconstruction on a Trichalcogenasumanene Buckybowl: A Facile Approach to Donor–Acceptor‐Type [5‐6‐7] Fused Planar Polyheterocycles

Abstract

The transformation of trichalcogenasumanene buckybowls into donor-acceptor-type [5-6-7] fused polyheterocycles is disclosed. The strategy involves a highly efficient ring-opening of the flanking benzene upon oxidation at room temperature, and facile ring closure by functional-group transformation. Crystallographic studies indicate that the resulting [5-6-7] fused polyheterocycles possess a planar conformation owing to the release of ring strain by expansion of one of the six-membered flanking rings to the seven-membered one. Additionally, the [5-6-7] fused polyheterocycles bear electron-withdrawing groups, which reduce the HOMO-LUMO energy gap, and display broad absorption bands extending to λ=590 nm. Consequently, these compounds show strong red emission with fluorescence quantum yields of up to 38 %.

Dissecting Trichalcogenasumanenes: π‐Bowl to Planar, Invertible Curvature, and Chiral Polycycles

“…We have disclosed the gram‐scale synthesis of hetero‐buckybowl trichalcogenasumanenes ( 1 a / 1 b in Scheme ) and found 1 a / 1 b show the cleavage of flanking benzene to give flat imides 2 a/2 b , respectively . To gain polycycles with diverse geometries and properties, here we report the precisely designed surgery on 1 a/1 b , aiming at the creation of [7‐5‐6]‐fused ( 4 a / 4 b ), [7‐6‐6]‐fused ( 5 a / 5 b ), and [7‐7‐6]‐fused ( 6 a / 6 b ) polycycles (Scheme ).…”

Synthesis of a peripherally conjugated 5-6-7 nanographene

“…The inclusion of 7-membered rings in PAH and related structures is known to affect the curvature and electronic conjugation of fused frameworks, however, the construction of such systems is still a non-routine task. 45 – 49 In conjunction with heteroatom doping, non-benzenoid fusion is an attractive method of increasing structural diversity in nanographenes. The rich chemistry of peripherally expanded azacoronenes 2–3 inspired us to seek synthetic designs that would produce systems with fully conjugated and non-trivial ring fusion patterns.…”

Trichalcogenasumanene ortho‐Quinones: Synthesis, Properties, and Transformation into Various Heteropolycycles

“…[17][18][19] Compounds 1a,b showed cleavage of one of the outer benzene rings upon oxidation with Oxone (path A), which led to the formation of various polycycles. [17][18][19] Compounds 1a,b showed cleavage of one of the outer benzene rings upon oxidation with Oxone (path A), which led to the formation of various polycycles.…”

“…We have disclosed previously that the chalcogen atoms play ap ivotal role in the chemical reactivity of 1a-c,a nd explored the regioselective transformation of these compounds. [17][18][19] Compounds 1a,b showed cleavage of one of the outer benzene rings upon oxidation with Oxone (path A), which led to the formation of various polycycles. [18] As for path B, the sulfur atoms of 1a were oxidized by H 2 O 2 to form tris(S,S-dioxide)trithiasumanene, [19] and the tellurium atoms of 1c formed ac ovalent adduct with halogens.…”

“…[17][18][19] Compounds 1a,b showed cleavage of one of the outer benzene rings upon oxidation with Oxone (path A), which led to the formation of various polycycles. [18] As for path B, the sulfur atoms of 1a were oxidized by H 2 O 2 to form tris(S,S-dioxide)trithiasumanene, [19] and the tellurium atoms of 1c formed ac ovalent adduct with halogens. [17] To gain further insight into the reactivity of trichalcogenasumanenes and explore new materials,w ei nvestigated the synthesis of trichalcogenasumanene ortho-quinones (2a,b in Scheme 2) through the selective transformation of butoxy groups (path C).…”