The linkage between reversible Friedel–Crafts acyl rearrangements and the Scholl reaction

Agranat, Israel; Oded, Yaacov Netanel; Mala’bi, Tahani; Pogodin, Sergey; Cohen, Shmuel

doi:10.1007/s11224-019-01368-z

Cited by 9 publications

(3 citation statements)

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“…AlCl 3 promoted the Scholl reaction, whereas PPA promoted the Friedel-Cra acylation. 52 In 2020, Jimenez and co-workers reported a method for the cyclodehydrogenation reaction of 2-substituted binaphthyls 56a and 56b to afford bay-substituted perylenes. Using AlCl 3 as the Lewis acid and high temperatures, the two new products 57a and 57b bearing NH 2 and N(CH 3 ) 2 groups at position 2 of the perylene ring were synthesized (Scheme 24).…”

Section: Alcl 3 and Cu(ii)-mediated Scholl Reactionmentioning

confidence: 99%

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Scholl reaction as a powerful tool for the synthesis of nanographenes: a systematic review

Jassas

Mughal

Sadiq³

et al. 2021

RSC Adv.

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Section: Alcl 3 and Cu(ii)-mediated Scholl Reactionmentioning

confidence: 99%

“…51 Scheme 23 AlCl 3 -mediated Scholl reaction of benzoylnaphthalene. 52 Scheme 24 Synthesis of perylene via the Scholl reaction. 53 Bushby and co-workers, in 2006, used FeCl 3 /methanol in dichloromethane (DCM) for triphenylene synthesis.…”

Section: Fecl 3 -Mediated Scholl Reactionmentioning

confidence: 99%

Scholl reaction as a powerful tool for the synthesis of nanographenes: a systematic review

Jassas

Mughal

Sadiq³

et al. 2021

RSC Adv.

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“…In the course of the reaction of 2 with TFA in dry . Friedel-Crafts reactions are known to be reversible [42][43][44][45][46][47][48] and compound 6 is very insoluble in the reaction mixture thus explaining the very high yield of 6 in these reactions. Previously, a retro Friedel-Crafts alkylation was used to access a fungal pigment from Peniophora sanguinea Bres [13].…”

Section: Introductionmentioning

confidence: 99%

In the Mists of a Fungal Metabolite: An Unexpected Reaction of 2,4,5-Trimethoxyphenylglyoxylic Acid

et al. 2020

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The reactions of phenylglyoxylic acids during the synthesis and biological evaluation of fungal metabolites led to the discovery of hitherto unknown compounds with a p-quinone methide (p-QM) structure. The formation of these p-QMs using 13 C-labelled starting materials revealed a key-step of this reaction being a retro-Friedel-Crafts alkylation.Molecules 2020, 25, 1978 2 of 15 catechol estrogen-o-quinones [11][12][13]. They are well known intermediates in the biosynthesis of natural products. Their high reactivity and potential has also been exploited in the total synthesis of some natural products such as the flavonoids rugaurone A-C [14] cherylline [15] and 20-deoxy-elansolid B1 [16]. Furthermore, the reactions of p-QMs have extensively been studied to generate compounds of pharmaceutical interest [17][18][19][20] and quite recently they were used as starting materials for an organo-catalytic asymmetric α-alkylation of aldehydes [21].During our research on metabolites from fungi and lichens we came across the chemical properties and reactions of phenylglyoxylic acids [22]. Thereby, we encountered several unexpected and unprecedented reactions yielding 3,3-diaryl substituted benzofuranones which undergo retro-Friedel-Crafts alkylation in hydrochloric acid forming the p-QM structure. These molecules are similar to 3,3-diaryloxoindoles and 3,3-substituted oxoindoles that have lately been studied quite extensively yielding pharmacological interesting molecules [23][24][25][26][27][28]; they are also known intermediates from isatines and a prominent motif in natural product products, as for example in azonazine [29]. In contrast to isatines, benzofuran-2,3-diones are widely overlooked [28,30]. This was another reason to provide an access to this rare structural motif. Results and DiscussionOxidation of 2,4,5-trimethoxy-acetophenone (1, Scheme 1) with SeO 2 [31] gave 2,4,5trimethoxyphenylglyoxylic acid (2); this compound has previously been isolated from the fungus Polyporus tumulosus Cooke [22,32]. As an alternative, a Friedel-Crafts acylation of 2,4,5-trimethoxybenzene (3) in the presence of TiCl 4 gave a 94% yield of ester 4 [33-35] whose hydrolysis with methanolic KOH for 2 h resulted in an almost quantitative yield of 2. Partial deprotection of the methoxy-groups with AlCl 3 of 2 yielded 5 albeit in low yields, while demethylation with either hydrobromic or hydrochloric acid yielded 6, a red colored solid in almost quantitative yield. A major issue in these reactions is the instability of the α-keto-acids that are readily decarboxylated [22,36]. These findings parallel previous reports for trimethoxy-substituted aromatic compounds [36]. Furthermore, α-keto acids were used for the synthesis of oxadiazolopyrazines-selective antibacterial agents against Haemophilus influenzae [37]. Attempts to cyclize 5 under a variety of different conditions invariably led to the formation of 6 in moderate to excellent yields. The formation of 7 was only observed to a rather minor extend by ESI-MS.

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General and Modular Synthesis of Covalent Organic Cages for Efficient Molecular Recognition

Zhao,

Cui,

Guo

et al. 2024

Angewandte Chemie

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Cage‐type structures based on coordination and dynamic covalent chemistry have the characteristics of facile and efficient preparation but poor stability. Chemically stable organic cages, generally involving fragment coupling and multi‐step reactions, are relatively difficult to synthesize. Herein, we offer a general and modular strategy to customize covalent organic cages with diverse skeletons and sizes. First, one skeleton (S) module with three extension (E) modules and three reaction (R) modules are connected by one‐ or two‐step coupling to get the triangular monomer bearing three reaction sites. Then one‐pot Friedel–Crafts condensation of the monomer and linking module of paraformaldehyde produces the designed organic cages. The cage forming could be regulated by the geometrical configuration of monomeric blocks. The S–E–R angles in the monomer is crucial; only 120o (2,4‐dimethoxyphen as reaction module) or 60o (2,5‐dimethoxyphen as reaction module) angle between S–E–R successfully affords the resulting cages. By the rational design of the three modules, a series of organic cages have been constructed. In addition, the host‐guest properties show that the representative cages could strongly encapsulate neutral aromatic diimine guests driven by solvophobic interactions in polar solvents, giving the highest association constant of (2.58 ± 0.18) × 105 M−1.

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The linkage between reversible Friedel–Crafts acyl rearrangements and the Scholl reaction

Cited by 9 publications

References 55 publications

Scholl reaction as a powerful tool for the synthesis of nanographenes: a systematic review

Scholl reaction as a powerful tool for the synthesis of nanographenes: a systematic review

In the Mists of a Fungal Metabolite: An Unexpected Reaction of 2,4,5-Trimethoxyphenylglyoxylic Acid

General and Modular Synthesis of Covalent Organic Cages for Efficient Molecular Recognition

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