Reversible Friedel-Crafts Acylations of Phenanthrene: Rearrangements of Acetylphenanthrenes

Levy, L; Pogodin, Sergey; Cohen, Shmuel; Agranat, Israel

doi:10.2174/157017807781212120

Cited by 13 publications

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“…Although the reaction has been known for more than 130 years it still receives attention [6-16] the recent interest being focused on the use of ionic liquids as solvents [7], selectivity studies [6,9,11,13], the application of solid catalysts [16], and still, mechanism details [8,12,14,15]. Simple aromatic hydrocarbons and methyl substituted derivatives have featured as substrates in both earlier and more recent studies of the reaction including benzenes [6,7,17-19], biphenyls and fluorene [11,13,20], naphthalenes [21-23], anthracenes [14,24,25], phenanthrenes [12,26], pyrenes [27], and chrysenes [28] and as a part of our continuing interest in Friedel-Crafts acetylations [11,13,21,28-31], we now report details of the acetylation of 3,3′-dimethylbiphenyl (3,3′-dmbp). Compounds and materials derived from this building block are of particular interest in the field of molecular liquid crystals [31], polymers [32,33] and metal-complexes [34].…”

Section: Resultsmentioning

confidence: 99%

A reactivity-selectivity study of the Friedel-Crafts acetylation of 3,3′-dimethylbiphenyl and the oxidation of the acetyl derivatives

Titinchi

Kamounah

Abbo

et al. 2012

Chemistry Central Journal

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BackgroundFriedel-Crafts acetylation is an important route to aromatic ketones, in research laboratories and in industry. The acetyl derivatives of 3,3′-dimethylbiphenyl (3,3′-dmbp) have applications in the field of liquid crystals and polymers and may be oxidized to the dicarboxylic acids and derivatives that are of interest in cancer treatment.FindingsThe effect of solvent and temperature on the selectivity of monoacetylation of 3,3’-dmbp by the Perrier addition procedure was studied using stoichiometric amounts of reagents. 4-Ac-3,3′-dmbp was formed almost quantitatively in boiling 1,2-dichloroethane and this is almost twice the yield hitherto reported. Using instead a molar ratio of substrate:AcCl:AlCl3 equal to 1:4:4 or 1:6:6 in boiling 1,2-dichloroethane, acetylation afforded 4,4′- and 4,6′-diacetyl-3,3′-dmbp in a total yield close to 100%. The acetyl derivatives were subsequently converted to the carboxylic acids by hypochlorite oxidation. The relative stabilities of the isomeric products and the corresponding σ-complexes were studied by DFT calculations and the data indicated that mono- and diacetylation followed different mechanisms.ConclusionsFriedel-Crafts acetylation of 3,3′-dmbp using the Perrier addition procedure in boiling 1,2-dichloroethane was found to be superior to other recipes. The discrimination against the 6-acetyl derivative during monoacetylation seems to reflect a mechanism including an AcCl:AlCl3 complex or larger agglomerates as the electrophile, whereas the less selective diacetylations of the deactivated 4-Ac-3,3′-dmbp are suggested to include the acetyl cation as the electrophile. The DFT data also showed that complexation of intermediates and products with AlCl3 does not seem to be important in determining the mechanism.

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Section: Resultsmentioning

confidence: 99%

A reactivity-selectivity study of the Friedel-Crafts acetylation of 3,3′-dimethylbiphenyl and the oxidation of the acetyl derivatives

Titinchi

Kamounah

Abbo

et al. 2012

Chemistry Central Journal

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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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Molecular Rearrangements: Part 2. Other Reactions

Brandi¹,

Gensini²

2011

Organic Reaction Mechanisms · 2008

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Reversible Friedel-Crafts Acylations of Phenanthrene: Rearrangements of Acetylphenanthrenes

Cited by 13 publications

References 0 publications

A reactivity-selectivity study of the Friedel-Crafts acetylation of 3,3′-dimethylbiphenyl and the oxidation of the acetyl derivatives

A reactivity-selectivity study of the Friedel-Crafts acetylation of 3,3′-dimethylbiphenyl and the oxidation of the acetyl derivatives

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

Molecular Rearrangements: Part 2. Other Reactions

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