Synthesis of [14]Oxatriphyrins(2.1.1) and Their Transformation into Ethane‐Bridged Oxatripyrrins by Boron Complexation

Kuzuhara, Daiki; Kawatsu, Shinsuke; Furukawa, Wataru; Hayashi, Hironobu; Aratani, Naoki; Yamada, Hiroko

doi:10.1002/ejoc.201800309

Cited by 16 publications

(9 citation statements)

References 71 publications

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“…2 a ( 2 b ) has a UV/Vis spectrum that is typical for aromatic porphyrinoids with a Soret‐like band at 415 nm (430 nm) and a set of Q bands that reach 600 nm (620 nm). The bands are red‐shifted by 40–50 nm compared to triphyrins(2.1.1) such as 1 b and 1 c , whose electron delocalization pathway is limited to 14 π electrons. The redshift suggests that the annelated C6 fragment is part of the π‐electron delocalization.…”

Section: Methodsmentioning

confidence: 72%

Aromatic and Antiaromatic Pathways in Triphyrin(2.1.1) Annelated with Benzo[b]heterocycles

Bartkowski

Dimitrova

Chmielewski

et al. 2019

Chemistry A European J

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Understanding of the aromatic properties and magnetically inducedc urrent densities of highlyc onjugated chromophores is importantw hen designing molecules with strongly delocalized electronic structure.L inear extension of the triphyrin(2.1.1) skeleton with an annelated benzo [b]heterocyclef ragment modifies the aromatic character by extending the electron delocalization pathway. Two-electron reduction leads to an antiaromatic triphyrin(2.1.1) ring and an aromatic benzo[b]heterocycles ubunit. Current-density calculations provide detailedi nformation about the observed pathways and their strengths.Extending the p-electron system in conjugated molecules is an important area of research, because the conjugation pathway exhibits notable influence on the opticala nd magnetic properties. [1] Linear extensions of the acene p cloud by annelation of molecular rings lead to different aromatic behavior of five-and six-membered rings. [3,4] As idef usion of af ive-membered ring to acene cores results in major differences in the electron delocalization with the bridging heteroatom separating the aromatic and antiaromaticmoieties. [5] Triphyrins(2.1.1) (Scheme 1) are triangularly shaped, contracted porphyrinoids whose structural constraints significantly affect their electronic properties. [2] The C2 bridge (1,S cheme1) makes it possible to merge an acene to the triphyrin macrocycle potentially resulting in molecular structures with novel optical andm agnetic properties as well as an unusual aromatic character. [2d,e] We have synthesized novel molecular structures with benzo[b]furan and benzo[b]thiophene annelated to triphyrin(2.1.1) (2,S cheme 1). The annelated arene ring may influence the global aromatic properties by incorporating the external ben-zoic (C6) ring into the delocalization pathway.T he synthesized macrocycles can also functiona sb oron(III)l igands forminga ntiaromatic complexes as shown in this work.Triphyrins 2a and 2b wereo btained by acid-catalyzed condensation of reagents 3a and 3b,r espectively.T hey were efficiently synthesized via Suzuki-Miyaura coupling from easily obtainable or commercially availables tarting materials (2,3-dibromobenzo[b]heterocyclea nd pyrrole-boronic acid), [6] followed by at hermolytic deprotection. [2d,e] 2a and 2b were isolated with ay ield of 10 %a nd 12 %, respectively.T he small coordination core of the macrocycle leads to av ery efficient entrapment of ap rotonm aking it possible to isolate the cationic form. As the counterion of the condensationp roduct was unknown,w ereplaced it with ac hloride anion by using ap reviously reported approach. [2d,e] Characterization and further studies were performed on the chloride derivatives. The X-ray analysis performed for 2b has confirmed the postulated pattern ( Figure S44).2a (2b)h as aU V/Vis spectrum that is typical for aromatic porphyrinoids with aS oret-like band at 415 nm (430 nm) and a set of Qb ands that reach 600 nm (620 nm). The bands are redshiftedb y4 0-50nmc ompared to triphyrins(2.1.1) such as 1b [2b] and 1c, [2f]...

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Section: Methodsmentioning

confidence: 72%

Aromatic and Antiaromatic Pathways in Triphyrin(2.1.1) Annelated with Benzo[b]heterocycles

Bartkowski

Dimitrova

Chmielewski

et al. 2019

Chemistry A European J

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“…In addition, [14]azulitriphyrin(2.1.1) 22a can be transformed into benzocarbatriphyrin(2.1.1) 23a, which shows porphyrin-like aromatic properties. 39 Ortho-phenylene and thiophene-fused oxatriphyrins(2.1.1) 25 were reported by Latos-Grażyński and co- 37 The Ravikanth group prepared the nonsymmetric benzene-fused oxatriphyrin(2.1.1) 28a and thiatriphyrin(2.1.1) 28b in four steps starting from 1-benzofuran and 1-benzothiophene, respectively (Scheme 11). 42 The nonaromatic dibenzofuran/dibenzothiophene-based triphyrins(2.2.1) 30a and 30b, and their Re(I) complex were also reported by the same group (Scheme 10).…”

Section: Account Synlettmentioning

confidence: 97%

“…The thiophene ring is tilted and two pyrroles form a nearly planar structure because steric hindrance between the lone pairs is canceled out and a hydrogen bond forms between the pyrroles as a result of protonation of a pyrrole ( Figure 2). [14]Oxatriphyrin(2.1.1) 19 37 and [14]azulitriphyrin(2.1.1) 22 38,39 were also obtained as their protonated forms for the same reason as 16. The angle of tilt of the furan in 19a is smaller than that of 16, reflecting the atomic radii ( Figure 2).…”

Section: Account Synlettmentioning

confidence: 99%

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Porphyrinoids with Vinylene Bridges

Kuzuhara

Yamada

2020

Synlett

Self Cite

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Porphyrinoids containing vinylene bridges, such as triphyrin(2.1.1), porphycene, porphyrin(2.1.2.1), and hexaphyrin(2.1.2.1.2.1), are a relatively new family of porphyrinoids. Vinylene bridges give porphyrinoids a lower symmetry and a flexibility of the framework and they permit cis/trans-isomerization reactions; these factors confer unique properties to these substances, such as coordination to metal ions and aromaticity switching. In this account, the synthesis, crystal structures, and properties of new porphyrinoids containing vinylene bridges are summarized.1 Introduction2 Triphyrin(2.1.1)3 Porphycene4 Porphyrin(2.1.2.1)5 Hexaphyrin(2.1.2.1.2.1)6 Conclusion

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“…Triphyrins are tripyrrolic analogues of porphyrins that include subporphyrins ([14]triphyrins(1.1.1), 7 ), , [14]triphyrins(2.1.1) 8 − (Figure ) and tripyrrolic macrocycles with 3–6 carbon bridges . [14]Triphyrins(1.1.1) can only be isolated as boron complexes, but these bowl-shaped 14π electron systems exhibit strong aromatic characteristics. , Larger triphyrin systems, such as 8 , can be isolated as free base structures and may also exhibit aromatic properties. − Triphyrins(2.1.1) can form complexes with boron, Mn(I), Re(I), Ru(II), Pd(II), and Ir(I), and also afford η 5 -cyclopentadienyliron(II) sandwich compounds. , In addition to the tripyrrolic system, thia- and oxatriphyrins(2.1.1) have also been reported. Triphyrins(2.1.1) were originally prepared by the acid-catalyzed condensation of a bicyclo[2.2.2]octadiene-fused pyrrole with aromatic aldehydes .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Azulitriphyrins(1.2.1) and Related Benzocarbatriphyrins

2019

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Bis(pyrrolylmethyl)azulene dialdehydes underwent intramolecularMcMurry coupling, and following oxidation with DDQ and addition of trifluoroacetic acid, gave aromatic azulitriphyrin cations. The proton NMR spectra for these contracted carbaporphyrinoids showed the internal CH upfield at ca. 2 ppm, while the bridging methine units appeared downfield between 8 and 10 ppm, demonstrating that the macrocycles possess significant 14π electron diamagnetic ring currents. Although protonated azulitriphyrins(1.2.1) proved to be very stable, the free base forms were unstable and could not be isolated. Treatment of an azulitriphyrin with KOt-Bu-t-BuOOH gave rise to oxidative ring contractions that afforded the first examples of benzocarbatriphyrins. These contracted porphyrinoids also exhibit aromatic ring currents, and the internal CH resonances shifted upfield to 0.5−0.7 ppm. Protonation afforded cations with slightly enhanced diatropic properties. Nucleus independent chemical shift and anisotropy of induced current density calculations confirmed that benzocarbatriphyrins are 14π electron delocalized aromatic systems that bypass the fused arene units.

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Synthesis of [14]Oxatriphyrins(2.1.1) and Their Transformation into Ethane‐Bridged Oxatripyrrins by Boron Complexation

Cited by 16 publications

References 71 publications

Aromatic and Antiaromatic Pathways in Triphyrin(2.1.1) Annelated with Benzo[b]heterocycles

Aromatic and Antiaromatic Pathways in Triphyrin(2.1.1) Annelated with Benzo[b]heterocycles

Porphyrinoids with Vinylene Bridges

Synthesis of Azulitriphyrins(1.2.1) and Related Benzocarbatriphyrins

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