The role of steric hindrance in the intramolecular oxidative aromatic coupling of pyrrolo[3,2-b]pyrroles

Krzeszewski, Maciej; Świder, Paweł; Cyrański, Michał K.; Danikiewicz, Witold; Gryko, Daniel T.

doi:10.1039/c6cc05904j

Cited by 23 publications

(16 citation statements)

References 35 publications

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“…As we mentioned in our previous papers, the extremely electron-rich character of the pyrrolo[3,2- b ]pyrrole scaffold is sometimes manifested by its unexpected reactiveness. 29 , 31 In Scheme 4 , we show another example of such a phenomenon. Looking for TAPPs with strongly polarized structures, we attempted the reaction of TAPP 18 with tetracyanoethylene (TCNE) in boiling toluene in the presence of pyridine, 32a which in line with our expectation resulted in the formation of compound 52 , however, only in a relatively small yield.…”

Section: Resultsmentioning

confidence: 90%

Method for the Large-Scale Synthesis of Multifunctional 1,4-Dihydro-pyrrolo[3,2-b]pyrroles

et al. 2020

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A thorough investigation has enabled the optimization of the synthesis of 1,4-dihydro-pyrrolo[3,2- b ]pyrroles. Although salts of such metals as vanadium, niobium, cerium, and manganese were found to facilitate the formation of 1,4-dihydro-pyrrolo[3,2- b ]pyrroles from amines, aldehydes, and diacetyl, we confirmed that iron salts are the most efficient catalysts. The conditions identified (first step: toluene/AcOH = 1:1, 1 h, 50 °C; second step: toluene/AcOH = 1:1, Fe(ClO 4 ) 3 ·H 2 O, 16 h, 50 °C) resulted in the formation of tetraarylpyrrolo[3,2- b ]pyrroles in a 6–69% yield. For the first time, very electron-rich substituents (4-Me 2 NC 6 H 4 , 3-(OH)C 6 H 4 , pyrrol-2-yl) originating from aldehydes and sterically hindered substituents (2-ClC 6 H 4 , 2-BrC 6 H 4 , 2-CNC 6 H 4 , 2-(CO 2 Me)C 6 H 4 , 2-(TMS-C≡C)C 6 H 4 ) present on anilines can be appended to the pyrrolo[3,2- b ]pyrrole core. It is now also possible to prepare 1,4-dihydropyrrolo[3,2- b ]pyrroles bearing an ordered arrangement of N -substituents and C -substituents ranging from coumarin, quinoline, phthalimide to truxene. These advances in scope enable independent regulations of many desired photophysical properties, including the Stokes shift value and emission color ranging from violet-blue through deep blue, green, yellow to red. Simultaneously, the optimized conditions have finally allowed the synthesis of these extremely promising heterocycles in amounts of more than 10 g per run without a concomitant decrease in yield or product contamination. Empowered with better functional group compatibility, novel derivatization strategies were developed.

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Section: Resultsmentioning

confidence: 90%

Method for the Large-Scale Synthesis of Multifunctional 1,4-Dihydro-pyrrolo[3,2-b]pyrroles

et al. 2020

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“…Tr eatment of bulky tetrabromo-substituted tetraarylpyrrolo[3,2-b]pyrrole 175 with FeCl 3 gave the spirocyclic cationic fluorene derivative 176 instead of the expected product with new six-membered rings (Scheme 27). [171] Computational studies revealed that, in the case of 175,t he formation of the spiro-five-membered ring is preferred in terms of both the transition-state energy and the relative energy of the product. Steric hindrance is undoubtedly the main reason for the different reactivity of compound 175 compared to its analogues that lack additional substituents on the peripheral benzene rings (e.g.…”

Section: Dyes and Heterocyclic Polyarenesmentioning

confidence: 99%

“…Treatment of bulky tetrabromo‐substituted tetraarylpyrrolo[3,2‐ b ]pyrrole 175 with FeCl 3 gave the spirocyclic cationic fluorene derivative 176 instead of the expected product with new six‐membered rings (Scheme ) . Computational studies revealed that, in the case of 175 , the formation of the spiro‐five‐membered ring is preferred in terms of both the transition‐state energy and the relative energy of the product.…”

Section: Intramolecular Oxidative Aromatic Couplingmentioning

confidence: 99%

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

et al. 2019

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Oxidative aromatic coupling occupies a fundamental place in the modern chemistry of aromatic compounds. It is a method of choice for the assembly of large and bewildering architectures. Considerable effort was also devoted to applications of the Scholl reaction for the synthesis of chiral biphenols and natural products. The ability to form biaryl linkages without any prefunctionalization provides an efficient pathway to many complex structures. Although the chemistry of this process is only now becoming fully understood, this reaction continues to both fascinate and challenge researchers. This is especially true for heterocoupling, that is, oxidative aromatic coupling with the chemoselective formation of a C−C bond between two different arenes. Analysis of the progress achieved in this field since 2013 reveals that many groups have contributed by pushing the boundary of structural possibilities, expanding into surface‐assisted (cyclo)dehydrogenation, and developing new reagents.

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“…Serendipitous discovery made in our laboratory in 2013 on the one-pot, multicomponent synthesis for 1,2,4,5-tetraarylpyrrolo[3,2- b ]pyrroles (TAPPs) opens up the possibilities for the formation of previously unknown π-expanded aza-analogs of PAHs 21 – 23 . A particularly suitable feature of this methodology is the fact that sterically congested ortho -substituted benzaldehydes give products in high yields, which makes this approach a powerful tool for the construction of highly conjugated molecules comprising pyrrolo[3,2- b ]pyrrole (PP) units 24 – 28 . Conversely, presence of two fused pentagonal rings in the center makes the pursuit of circularly conjugated species particularly complex, since it requires thermodynamically demanding closure of two heptagonal rings.…”

Section: Introductionmentioning

confidence: 99%

On-surface synthesis of a nitrogen-embedded buckybowl with inverse Stone–Thrower–Wales topology

et al. 2018

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Curved π-conjugated polycyclic aromatic hydrocarbons, buckybowls, constitute an important class of materials with wide applications in materials science. Heteroatom doping of buckybowls is a viable route to tune their intrinsic physicochemical properties. However, synthesis of heteroatom-doped buckybowls is a challenging task. We report on a combined in-solution and on-surface synthetic strategy toward the fabrication of a buckybowl containing two fused nitrogen-doped pentagonal rings. We employ ultra-high-resolution scanning tunneling microscopy and spectroscopy, in combination with density functional theory calculations to characterize the final compound. The buckybowl contains a unique combination of non-hexagonal rings at its core, identified as the inverse Stone–Thrower–Wales topology, resulting in a distinctive bowl-opening-down conformation of the buckybowl on the surface. Our controlled design of non-alternant, heteroatom-doped polycyclic aromatic frameworks with established bottom-up fabrication techniques opens new opportunities in the synthesis of carbon nanostructures with the perspective of engineering properties of graphene-based devices.

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The role of steric hindrance in the intramolecular oxidative aromatic coupling of pyrrolo[3,2-b]pyrroles

Cited by 23 publications

References 35 publications

Method for the Large-Scale Synthesis of Multifunctional 1,4-Dihydro-pyrrolo[3,2-b]pyrroles

Method for the Large-Scale Synthesis of Multifunctional 1,4-Dihydro-pyrrolo[3,2-b]pyrroles

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

On-surface synthesis of a nitrogen-embedded buckybowl with inverse Stone–Thrower–Wales topology

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