Crafts Chemistry Research Articles

Friedel–Crafts Chemistry. Part 63. Syntheses of some condensed N-heterocyclic systems via combined Darzens and Friedel-Crafts approaches

Friedel–Crafts Chemistry. Part 63. Syntheses of some condensed N-heterocyclic systems via combined Darzens and Friedel-Crafts approaches

Guided Assembly of Well-Defined Hierarchical Nanoporous Polymers by Lewis Acid-Base Interactions.

Three-dimensional hierarchical nanoporous polymers and carbon nanomaterials with well-defined superstructures are of great interest for various intelligent applications, whereas a facile and versatile approach to access those materials with a high surface area, stable well-defined morphology, and ordered pores still remains a significant challenge. Herein, we report a self-regulated Lewis acid-base interaction-mediated assembly strategy for the in situ synthesis of morphology-engineered hyper-cross-linked porous polymers and carbon materials. A series of functionalized aromatic compounds (FAC) is subjected to self-cross-linking via classic Friedel-Crafts chemistry to achieve stable porous polymers with a high surface area. Varying the monomer/catalyst combination had a dramatic effect on the acid-base interaction, facilitating the tailoring of the self-assembled morphologies from nanotubes to hollow nanospheres, and even nanosheets. A mechanistic study showed that the byproducts generated during cross-linking orchestrate the interactions between the catalyst (acid) and FAC (base) and simultaneously drive the self-assembly to yield specific morphologies. Based on the rigid hollow polymer framework and intrinsic hydroxyl functionality, the hyper-cross-linked hollow nanospheres were easily transformed to an acid-functionalized catalyst for efficient biodiesel production. Moreover, high-quality porous carbonaceous nanocounterparts such as carbon nanotubes, hollow carbon nanospheres, and carbon nanosheets could also be produced by direct pyrolysis of the corresponding polymer precursors. These findings may provide guidance for the facile design of morphology-controlled functionalized polymers and carbon nanomaterials for various applications.

Friedel–Crafts chemistry 56*. Unprecedented construction of functionalized polycyclic quinolines via Friedel–Crafts cycliacylation and Beckmann rearrangement

Construction of functionalized tetracyclic pyrazolo-fused cyclohepta[2,3-h]-, azepino[4,5-h]-, azocino[5,4-h]-, azocino[4,5-h]-, azonino[5,6-h]-, and azocino[2,3-h]quinolinones has been demonstrated by performing intramolecular Friedel–Crafts acylation and Beckmann rearrangement. Trifluoromethanesulfonic or polyphosphoric acid-assisted cyclization of N-heterocyclic acids and esters, synthesized from 1-phenyl-3-(quinolin-8-yl)-1H-pyrazole-4-carbaldehyde, allows to obtain tetracyclic ketones. Further polyphosphoric acid-mediated Beckmann rearrangement of cyclohepta[1,2-h]quinolinone oximes provides the respective lactams in high yields.

Friedel–Crafts Chemistry. Part 53. Divergent and Diversity-Oriented Synthesis of Condensed Indole Scaffolds via Friedel–Crafts Ring Closure Approach

A series of indole-fused medium-sized N-heterocyclic systems 10a–h were prepared from laboratory-synthesized indole-based esters 9a–h via intramolecular Friedel–Crafts cyclizations induced by both trifluoromethanesulfonic acid and AlCl3/CH3NO2 catalysts under suitable conditions. The synthetic sequence to precursors 9a–h that started from simple N-methylindole-2-carboxylic acid involved conversion to aminoindoles 2a, b, reaction with α,β-unsaturated acid chlorides to yield acyclic amides 5a–d, ring closure to tricyclic lactams 6a–d, and carbonyl reduction to respective pyrido and azepino tricyclic amines 7a–d, which finally underwent N-alkylations with α- or β-haloesters to produce the required ester precursors. The structures of synthesized compounds without stereochemical implications are established using both spectral and analytical data.

Friedel–Crafts Chemistry. Part 48. Concise Synthesis of Condensed Azaheterocyclic [1,8]naphthyridinones, Azepino-, Azocino-, and Azoninoquinoline Systems via Friedel–Crafts Ring Closures

Unprecedented construction of a novel series of quinoline heteropolycycles (tetracyclic keto-analogues of [1,8]naphthyridinones, azepino-, azocino- and azonino[2,3-b]quinolinones systems) 10a–i by Friedel–Crafts cycliacylation reactions is described. Starting heterocyclic acids precursors 3a–i were prepared from easily accessible 2-chloroquinoline-3-carbaldehyde 1 via a three different synthetic pathways. Acid-catalyzed ring closures of the resulting tosylated acids were achieved under the influence of both Brønsted and Lewis acid catalysts. The present strategy enables a straightforward synthesis to fused tetracyclic quinolinone skeletons as demonstrated by concise and atom-economical syntheses.

ChemInform Abstract: Polystyrene or Magnetic Nanoparticles as Support in Enantioselective Organocatalysis? A Case Study in Friedel—Crafts Chemistry.

AbstractThe efficiency of the second‐generation MacMillan organocatalyst onto slightly cross‐linked polystyrene or iron oxide magnetic nanoparticles is evaluated in the enantioselective Friedel—Crafts alkylation of indoles with α,β‐unsaturated aldehydes.

Heterogeneous Catalytic Hydroarylation of Olefins at a Nanoscopic Aluminum Chlorofluoride

AbstractWe report on hydroarylation reactions of arenes with olefins under very mild conditions catalyzed heterogeneously by aluminum chlorofluoride (ACF; AlClxF3−x, x≈0.05–0.25). The reactions of benzene and toluene with ethylene or propylene proceed with high conversions to afford various alkylated arenes. For cyclohexene and 1‐hexene, the reactions require higher temperatures and the conversions are lower. ACF also catalyzes the hydroarylation of 1,3,5‐trifluorobenzene and pentafluorobenzene with ethylene and propylene. The alkylations of arenes with non‐fluorinated olefins resemble typical Friedel–Crafts chemistry to give rise to Markovnikov regioselectivity. The reaction of CF3CH=CH2 with benzene proceeds with anti‐Markovnikov regioselectivity to give the fluorinated olefin PhCHCH=CF2 and the alkylation product PhCH2CH2CF3 as products of C−F and C−H activation.

Polystyrene or Magnetic Nanoparticles as Support in Enantioselective Organocatalysis? A Case Study in Friedel-Crafts Chemistry.

Heterogenized versions of the second-generation MacMillan imidazolidin-4-one are described for the first time. This versatile organocatalyst has been supported on 1% DVB Merrifield resin and Fe3O4 magnetic nanoparticles through a copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. The resulting catalytic materials have been successfully applied to the asymmetric Friedel-Crafts alkylation of indoles with α,β-unsaturated aldehydes. While both catalytic systems can be easily recovered and admit repeated recycling, the polystyrene-based catalyst shows higher stability and provides better stereoselectivities.

Cross-Conjugated n-Dopable Aromatic Polyketone

This paper describes the synthesis and characterization of a high molecular weight cross-conjugated polyketone synthesized via scalable Friedel–Crafts chemistry. Cross-conjugated polyketones are precursors to conjugated polyions; they become orders of magnitude more conductive after a two-electron reduction and demonstrate reversible spinless doping upon protonation with acids. Cross-conjugated polyketones are a new polymer platform that possess the same optoelectronic tunability as conventional polymers but with excellent thermal and oxidative stability. We constructed a proof-of-concept organic light-emitting diode device and demonstrate that a cross-conjugated polyketone can be successfully used as an n-dopable semiconducting material.

Preparation of hierarchically porous carbon nanofoams for electrode materials of supercapacitors

Hierarchically porous carbon nanofoams were prepared via the formation of core–shell organosilica nanoparticles and subsequent Friedel–Crafts chemistry. The specific capacitance of them as electrode materials reached 170 F g−1 in an aqueous electrolyte.

Friedel–Crafts Chemistry. Part 43. A Convergent Construction of Some New Bridged Aza-Bicyclic Analogues of Azocine, Azonine, and Azecine via Friedel–Crafts Ring Closures

Our present study provides an expedient general approach for the synthesis of some novel bridged dibenzo-azocinone, -azoninone, -azecinone, -azocine, -azonine, and -azecine derivatives via Friedel–Crafts intramolecular ring-closure reactions. The methodology is realized by a four-step protocol involving first preparation of 7-methyl-3,3-diphenylindoline through the reduction of 7-methyl-3,3-diphenylindolin-2-one followed by N-alkylations with different haloesters (α-, β- or γ-). The resulting indoline ester derivatives were allowed to react both by addition of Grignard reagents to afford alcohols and by hydrolysis to afford acids. Particular attention has been given to the novel structures especially in regard to the promising pharmaceutical and therapeutic values associated with their skeletons.

Stabilizing cations in the backbones of conjugated polymers

We synthesized a cross-conjugated polymer containing ketones in the backbone and converted it to a linearly conjugated, cationic polyarylmethine via a process we call “spinless doping” to create a new class of materials, conjugated polyions. This process involves activating the ketones with a Lewis acid and converting them to trivalent cations via the nucleophilic addition of electron-rich aryl moieties. Spinless doping lowers the optical band gap from 3.26 to 1.55 eV while leaving the intrinsic semiconductor properties of the polymer intact. Electrochemical reduction (traditional doping) further decreases the predicted gap to 1.18 eV and introduces radicals to form positive polarons; here, n-doping produces a p-doped polymer in its metallic state. Treatment with a nucleophile (NaOMe) converts the cationic polymer to a neutral, non-conjugated state, allowing the band gap to be tuned chemically, post-polymerization. The synthesis of these materials is carried out entirely without the use of Sn or Pd and relies on scalable Friedel–Crafts chemistry.

Total syntheses and cytotoxicity of kealiiquinone, 2-deoxy-2-aminokealiiquinone and analogs

Concise syntheses of two Leucetta-derived naphthimidazole alkaloids, kealiiquinone and 2-deoxy-2-aminokealiiquinone, are described based on a biosynthetic-guided hypothesis. Advanced intermediates containing the full naphthimidazole framework are constructed through Friedel–Crafts chemistry followed by oxidation of the electron rich C-ring with hydrogen peroxide. The cytotoxicity of these alkaloids in a breast cancer cell line along with several closely related marine-derived natural products kealiinines A–C and analogs are reported.

Friedel–Crafts Chemistry. Part 39. Unprecedented Facile Route to the Synthesis of Benzo[b][1]benzazepines via Intramolecular Friedel–Crafts Cyclialkylations

A series of six pharmaceutically promising 5,6-dihydro-11H-benzo[b][1]benzazepine derivatives (1c–h) were cleanly prepared by Friedel–Crafts cyclialkylations of nitrogen-containing alkanols in the presence of AlCl3, 85 % H2SO4 or polyphosphoric acid catalysts. The precursor alkanols (13a–f) were readily prepared by reaction of two synthesized carboxylic acid esters (12a, b) with different Grignard reagents. Also, two dibenzo[b,f]azepinones (15a, b) were prepared by Friedel–Crafts cycliacylation and reduced to the corresponding 5,6-dihydro-11H-benzo[b][1]benzazepines (1a, b). Overall, this approach allows easy and efficient access to polytricyclic amines from easily synthesized alkanols or cycloketones. A plausible carbocation mechanism is proposed to account for the results.

ChemInform Abstract: Modern Friedel—Crafts Chemistry. Part 30. Facile Synthesis of Isomeric Tri‐ and Tetramethyltetrahydrophenanthrenes via Rearranged Cycloalkylation of Suitably Methylated 1‐(1‐ and 2‐Naphthyl)‐3‐pentanols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Modern Friedel—Crafts Chemistry. Part 29. Cyclialkylation of Some Triphenylated Propane, Butane and Pentane Substrates to Diphenylated Indans under Friedel—Crafts Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Modern Friedel—Crafts Chemistry. Part 27. Alkylation of Benzene with 1‐Benzyl‐ and 1‐Phenylcyclohexanols in the Presence of H2SO4 and AlCl3/CH3NO2 Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Development of acid stable, hyper-crosslinked, silica-based reversed-phase liquid chromatography supports for the separation of organic bases

A new generation of extremely acid stable “hyper-crosslinked” (HC) phases have been developed with good plate counts for basic drug separations. In our previous work, we successfully developed an approach for synthesizing HC stationary phases on silica substrates using aluminum trichloride catalyzed Friedel–Crafts (F–C) chemistry to improve the stability of silica-based RPLC stationary phases at low pH. However, the performance of basic analytes on these HC phases under acidic conditions was unusually poor compared to that of conventional silica-based C 18 phases. The effects of the specific F–C catalysts used and the specific silica substrate on the chromatographic properties of HC phases have been studied. Modified synthetic strategies that give both good observed plate counts for basic analytes under acidic conditions and very good low pH stability without compromising other chromatographic properties of the hyper-crosslinked phases have been developed. Replacement of aluminum trichloride with tin tetrachloride as the catalyst for the F–C chemistry and use of a very high purity silica result in significantly improved plate counts for basic analytes. In formic acid buffered mobile phases, which are highly compatible with electrospray ionization LC–MS, basic analytes showed much better performance on the tin tetrachloride catalyzed HC phases than on any conventional commercial phase tested. The tin tetrachloride catalyzed HC phase is as stable as the original aluminum trichloride catalyzed HC phases, and much more stable than the bench mark acid stable commercial phase.

Synthetic Studies toward the Haouamines

[reaction: see text] A concise synthetic approach toward the haouamines based on Stork-Danheiser alkylation and Friedel-Crafts chemistry is described. A novel electrophilic aromatic substitution with concomitant formation of an enol triflate is reported.

Modern Friedel—Crafts Chemistry. Part 26. A Facile Synthesis of trans‐2‐Methyl‐1‐phenylindan via Rearranged Intramolecular Cycloalkylation of 1,2‐Diphenyl‐2‐methyl‐2‐propanol under Friedel—Crafts Conditions.

AbstractFor Abstract see ChemInform Abstract in Full Text.