Late-Stage Modification of Electronic Properties of Antiaromatic and Diradicaloid Indeno[1,2-<i>b</i>]fluorene Analogues via Sulfur Oxidation

Dressler, Justin J.; Barker, Joshua E.; Karas, Lucas J.; Hashimoto, Hannah; Kishi, Ryohei; Zakharov, Lev N.; MacMillan, Samantha N.; Gómez‐García, Carlos J.; Nakano, Masayoshi; Wu, Judy I.; Haley, Michael M.

doi:10.1021/acs.joc.0c01387

Cited by 24 publications

(13 citation statements)

References 78 publications

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“…31 We recently uncovered the reasons for the stronger paratropicity in the syn isomer, which is due to a Clar sextet effect. 40 Finally, NICS-XY scans of thiophene and its benzo and naphtho analogues (Figure S7 of the Supporting Information) show that the diatropicity of the heterocycle is weakest in naphtho[2,3-b]thiophene, meaning its S atom can π donate into the s-indacene core more effectively, enhancing its paratropicity. 28 Taken together, this illustrates why the syn-linear fusion of naphthothiophene affords the most antiaromatic NICS values.…”

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confidence: 76%

Enhancing the Antiaromaticity of s-Indacene through Naphthothiophene Fusion

et al. 2021

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Addressing the instability of antiaromatic compounds often involves protection with bulky groups and/or fusion of aromatic rings, thus decreasing paratropicity. We report four naphthothiophene-fused s-indacene isomers, one of which is more antiaromatic than parent s-indacene. This surprising result is examined computationally through nucleus-independent chemical shift XY calculations and experimentally via nuclear magnetic resonance spectroscopy, X-ray crystallography, ultraviolet−visible spectrophotometry, and cyclic voltammetry, with the latter two indicating that this molecule possesses the lowest highest occupied molecular orbital−lowest unoccupied molecular orbital energy gap observed for heterocycle-fused sindacene.

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confidence: 76%

Enhancing the Antiaromaticity of s-Indacene through Naphthothiophene Fusion

et al. 2021

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“…[10][11][12][13] This latter property makes PA AHs interesting synthetic targets for electronics applications, [14,15] as recent reports of organic field effect transistors fabricated with PA AHs have shown good hole mobilities (> 1cm 2 V À1 s À1 ). [16][17][18][19] Astrategy for stabilization of antiaromatic moieties,t hat also enables greater functionalization within structure-activity relationship (SAR) studies,istofuse aryl groups,specifically heterocycles, to reactive positions of the antiaromatic structure.E xamples of this strategy include studies of pentalenes, [7,[20][21][22] s-indacenes, [23][24][25][26][27][28] and even the synthesis of planar antiaromatic cyclooctatetraene derivatives. [9,10] Fusion of thieno-heterocycles have dominated these reports and as aresult there has been limited exploration of the effects of changing the heteroatoms in these systems.…”

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confidence: 99%

A Tale of Two Isomers: Enhanced Antiaromaticity/Diradical Character versus Deleterious Ring‐Opening of Benzofuran‐fused s‐Indacenes and Dicyclopenta[b,g]naphthalenes

et al. 2021

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We examine the effects of fusing two benzofurans to s-indacene (indacenodibenzofurans,I DBFs) and dicyclopenta[b,g]naphthalene (indenoindenodibenzofurans, IIDBFs) to control the strong antiaromaticity and diradical character of these core units.S ynthesis via 3-functionalized benzofuran yields syn-IDBF and syn-IIDBF.s yn-IDBF possesses ah igh degree of paratropicity,e xceeding that of the parent hydrocarbon, which in turn results in strong diradical character for syn-IIDBF.I nt he case of the anti-isomers, synthesized via 2-substituted benzofurans,t hese effects are decreased;h owever,b oth derivatives undergo an unexpected ring-opening reaction during the final dearomatization step. All the results are compared to the benzothiophene-fused analogues and showt hat the increased electronegativity of oxygen in the syn-fused derivatives leads to enhancement of the antiaromatic core causing greater paratropicity.F or syn-IIDBF increased diradical character results from rearomatization of the core naphthalene unit in order to relieve this paratropicity.

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“…A serious challenge is to establish a rational design for a suitable molecular series possessing both open‐shell and antiaromatic characteristics. A lack of rational design guidelines is a major obstacle to advance the understanding of the interrelation between the open‐shell and antiaromatic characteristics [37,38] …”

Section: Introductionmentioning

confidence: 99%

Characterization of Benzo[a]naphtho[2,3‐f]pentalene: Interrelation between Open‐shell and Antiaromatic Characters Governed by Mode of the Quinoidal Subunit and Molecular Symmetry

Konishi

Horii

Iwasa

et al. 2021

Chemistry An Asian Journal

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The singlet open‐shell character and antiaromaticity are intriguing features in π‐conjugated carbocycles. These two exhibit similar chemical and physical properties. However, they rarely coexist in the same molecule. Understanding the interrelation between the open‐shell and antiaromatic characteristics in the same molecule is crucial to control the electronic properties. Herein we describe the synthesis and characterization of a new member of diareno[a,f]pentalene, benzo[a]naphtho[2,3‐f]pentalene 6. Unlike its isomer 5 with a closed‐shell ground state, 6 exhibits an appreciable open‐shell character and a moderate antiaromatic feature. The behaviors of the open‐shell index (y0) against the difference of the proton chemical signal (Δδ(H1)) between pentalenide dianions/neutral pentalenes for our reported pentalenes 1, 4, 5, and 6 give a thought‐provoking conclusion about the interrelation between open‐shell and antiaromatic characteristics in this series. The mode of the incorporated quinoidal moiety and the formal molecular symmetry are critical to balance these two characteristics.

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Late-Stage Modification of Electronic Properties of Antiaromatic and Diradicaloid Indeno[1,2-b]fluorene Analogues via Sulfur Oxidation

Cited by 24 publications

References 78 publications

Enhancing the Antiaromaticity of s-Indacene through Naphthothiophene Fusion

Enhancing the Antiaromaticity of s-Indacene through Naphthothiophene Fusion

A Tale of Two Isomers: Enhanced Antiaromaticity/Diradical Character versus Deleterious Ring‐Opening of Benzofuran‐fused s‐Indacenes and Dicyclopenta[b,g]naphthalenes

Characterization of Benzo[a]naphtho[2,3‐f]pentalene: Interrelation between Open‐shell and Antiaromatic Characters Governed by Mode of the Quinoidal Subunit and Molecular Symmetry

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