Synthesis of functionalized 2-oxindoles by Friedel–Crafts reactions

Gasonoo, Makafui; Klumpp, Douglas A.

doi:10.1016/j.tetlet.2015.06.028

Cited by 11 publications

(4 citation statements)

References 24 publications

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“…Thus, the aim of this work is to report the gas separation performances of six POXINARs synthesized by polymerization of isatines ( 1a or 1b ) with various aromatic hydrocarbons (H–Ar–H) to produce polymers 2aA–D , 2bC , 2bE and 2bF according to the reaction scheme shown in Figure . Highly efficient reactions of isatin with aromatics have been reported. , and although a variety of aromatic monomers could be used in polycondensation with isatin, for this work, a set of six monomers was chosen to determine the main structural factors determining the gas separation performances of POXINAR membranes.…”

Section: Introductionmentioning

confidence: 99%

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POXINAR Membrane Family for Gas Separation

Cetina-Mancilla

Hernández-Martínez

Zolotukhin

et al. 2019

Ind. Eng. Chem. Res.

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Poly(oxindolylidene arylene)s (POXINARs), a family polymers with high performance in terms of thermal stability properties and with ether-bond-free aromatic backbones alternating with bulky, torsion resistant oxindolylidene fragments, have been synthesized by superacid catalyzed polyhydroxyalkylation, and their useful physical properties have been assessed to determine their performance as gas separation membranes. The room temperature synthesis allows a variety of fully soluble, high-molecular-weight polymers in a single pot “click” reaction. These polymers can form flexible and transparent films, and they possess high glass transition temperatures (>500 °C); high decomposition temperatures (ranging from 500 to 524 °C); and FFVs (0.130–0.194) comparable to those reported for the polysulfone, polycarbonate, and polyarylate families. However, their selectivity–permeability combinations are very attractive because some fall close to the 2008 upper-bound limits. Membranes made from isatin and 9,9-dimethyl-9H-fluorene (2aD) display P(O2) = 15.4 Barrer for the O2/N2 gas pair and an O2/N2 selectivity of 6.4, whereas for the H2/CH4 gas pair, they display P(H2) = 170 Barrer and a H2/CH4 selectivity of 77.

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Section: Introductionmentioning

confidence: 99%

“…Highly efficient reactions of isatin with aromatics have been reported. 11,12 and although a variety of aromatic monomers could be used in polycondensation with isatin, for this work, a set of six monomers was chosen to determine the main structural factors determining the gas separation performances of POXINAR membranes.…”

Section: Introductionmentioning

confidence: 99%

POXINAR Membrane Family for Gas Separation

Cetina-Mancilla

Hernández-Martínez

Zolotukhin

et al. 2019

Ind. Eng. Chem. Res.

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“…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].…”

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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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“…To our knowledge, this is the first time a dehydro DKP has been used as a nucleophilic partner in a reaction with an isatin derivative. Creation of the quaternary center required trapping the stabilized carbocation intermediate formed upon ionization of the tertiary alcohol group in 15 with indole as a π-nucleophile . After some experimentation, we discovered that the O -silylated derivative of 15 , which was generated in situ, underwent facile ionization and reaction with indole in the presence of excess TMSOTf to deliver 16 as a single diastereomer in 86% yield .…”

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Syntheses of Gliocladin C and Related Alkaloids

Hodges¹,

Benjamin²,

Martin

2017

Org. Lett.

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A unique approach to gliocladin C and related alkaloids was developed that features an unprecedented nucleophilic addition of a diketopiperazine to an isatin derivative followed by a Friedel-Crafts alkylation of the resultant tertiary alcohol with indole to set the key quaternary center. Chemoselective oxindole reduction and cyclization delivered a pivotal hexahydropyrrolo[2,3-b]indole diketopiperazine intermediate that was readily converted into (±)-gliocladin C, (±)-T988C, and (±)-gliocladine C, culminating in the shortest approach to these alkaloids reported to date.

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Synthesis of functionalized 2-oxindoles by Friedel–Crafts reactions

Cited by 11 publications

References 24 publications

POXINAR Membrane Family for Gas Separation

POXINAR Membrane Family for Gas Separation

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

Syntheses of Gliocladin C and Related Alkaloids

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