Synthesis of new thioxanthenes by organocatalytic intramolecular Friedel–Crafts reaction

An efficient organocatalytic route has been developed to synthesize novel substituted thioxanthenes (2a–2v) starting from diaryl thioether alcohols (1a–1v) using the intramolecular Friedel–Crafts reaction. The starting materials were obtained in two stages via a coupling reaction followed by the Grignard reaction. In this study, we tried for the first time to use some organic Brønsted acids as organocatalysts (3a–3h) in the intramolecular Friedel–Crafts cyclization reaction of thioether alcohols. The synthesis of original substituted thioxanthenes was achieved within 15?minutes by using N-triflylphosphoramide (3h) with quantitative yields in THF at room temperature.     

Synthesis of extended π-conjugated hypercrosslinked polymers via a Friedel–Crafts reaction and an intramolecular Scholl coupling reaction

Long-range conjugated structures are important for increasing the conductivity and broadening the application scope of hypercrosslinked polymers (HCPs). It is, however, difficult to fabricate long-range conjugated structures using conventional HCP synthesis methods. Herein, we report a simple and efficient strategy for the synthesis of HCPs with extended π-conjugated structures through Friedel–Crafts and intramolecular Scholl-coupling reactions from readily available aromatic compounds under mild conditions. Two conjugated HCPs (C-HCPs), namely, C-HCP-ATA and C-HCP-TPB, were prepared from anthracene (ATA) and triphenylbenzene (TPB), respectively, using this method. The proposed strategy not only ensures a high specific surface area of materials but also introduces a long-range conjugated structure into HCPs. The lithium-ion battery applications of the C-HCPs were investigated. As anode materials, C-HCP-ATA and C-HCP-TPB displayed higher lithium storage capacities, better conductivity, and higher stability than their precursors, HCP-ATA and HCP-TPB, which were prepared using the conventional method.     

Synthesis of functionalized 3-chloro-1-naphthols via Friedel–Crafts acylation of vinyl chlorides

Friedel–Crafts type cyclization of vinyl chlorides was developed into a general method for the synthesis of functionalized naphthols. The chloro functional group contained within these products allowed for further elaboration via cross-coupling reactions, leading to increased structural complexity.     

Highly stereoselective imidazolethiones mediated Friedel–Crafts alkylation of indole derivatives

The asymmetric Friedel–Crafts alkylation of indoles with α,β-unsaturated aldehydes was promoted by the novel imidazolethiones to afford the corresponding adducts in moderate to excellent yields and high enantioselectivities under mild reaction conditions.     

Efficient Friedel–Crafts benzoylation of aniline derivatives with 4-fluorobenzoyl chloride using copper triflate in the synthesis of aminobenzophenones

An efficient pathway for the synthesis of the aminobenzophenone derivatives via Friedel–Crafts benzoylation using copper triflate as catalyst is proposed. New derivatives are synthesized. The copper triflate could be easily recovered and reused without loss of catalytic activity. Both the use of ionic liquids and microwave heating turned out to be fruitful.     

Synthesis of N-Heteropolycyclic Compounds Including Quinazolinone Skeleton Using Friedel–Crafts Alkylation

A simple method to synthesize N-heteropolycyclic quinazolinones was developed including Knoevenagel condensation of quinazolines and aldehydes and Friedel–Craft alkylation as key steps. Knoevenagel reaction of 2-methyl-3-phenylquinazolin-4(3H)-one proceeded smoothly under a basic condition and subsequent Friedel–Craft alkylation with Brønsted acid gave the N-heteropolycyclic quinazolinones in good yields. Furthermore, these new polycyclic compounds were converted into organic molecules having a long π-conjugation system by treatment of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) to utilize them as organic dyes.     

Synthesis of highly substituted indene derivatives by Brønsted acid catalyzed Friedel–Crafts reaction of homoallylic alcohols

An efficient synthetic method to prepare highly substituted indenes in moderate to excellent yields that relies on Brønsted acid catalyzed Friedel–Crafts reaction of homoallylic alcohols under mild conditions is described.     

Synthesis of tricyclic compounds via sequential intramolecular Michael addition and alkylation of β-ketoester ynones

Base-catalyzed sequential intramolecular Michael addition and alkylation of cyclic β-ketoester ynones 1 (n = 1,2) produce the corresponding tricycles 3 via intermediate enone-anions 2.     

Total synthesis of agomelatine via Friedel–Crafts acylation followed by Willgerodt–Kindler reaction

Total synthesis of antidepressant drug, agomelatine is reported. Regio selective Friedel–Crafts acylation followed by Willgerodt–Kindler reactions is used as the key steps for the synthesis of agomelatine.     

Synthesis and photophysical evaluations of β-fused uracil-porphyrin derivatives

New β-fused uracil-porphyrin conjugates were synthesized by the tetramerization of uracil-pyrroles under acidic conditions. Two different synthetic approaches were systematically studied in order to evaluate their efficiency, as well as the possibility to obtain a single regioisomer. Metallation effects were studied for aggregation in solution, and preliminary photophysical experiments were also performed in order to evaluate the potential of these new compounds.     

Bismuth Triflate–Catalyzed Friedel–Crafts Acylations of Sydnones

Friedel–Crafts acylations of various 3-arylsydnones at the C4 position have been achieved in good yields using 4 equivalents of an alkyl anhydride and 25 mol% each of bismuth triflate and lithium perchlorate in anhydrous acetonitrile at 95 °C. Acylations appear to be faster with arylsydnones bearing electron-donating moieties and sterically unencumbered anhydrides.     

Synthesis of furan derivatives of cyclic β-amino acid cispentacin via intramolecular nitrile oxide cycloaddition

Two furan derivatives of cispentacin have been synthesized starting from a d-mannitol derived conjugated nitroolefin through intramolecular nitrile oxide cycloaddition (INOC) as a key step.     

Synthesis of new 4-methyl-3-piperidones via an iron-catalyzed intramolecular tandem isomerization–aldolisation process

A new versatile synthesis of 3-piperidones is described, starting from amino acids. It uses, as a key step, an iron carbonyl-mediated intramolecular tandem isomerization–aldolisation reaction. These new heterocycles appear as useful scaffolds for the total synthesis of various types of bioactive molecules.     

Synthesis of porous aromatic framework with Friedel–Crafts alkylation reaction for CO_2 separation

A novel porous aromatic framework, PAF-8, derived from tetraphenylsilane as basic building unit, was successfully synthesized via Friedel–Crafts alkylation reaction. This PAF material had high thermal stability as well as high surface area(785 m~2g~(-1)) calculated from the Brunauer–Emmett–Teller(BET)model. Meanwhile, PAF-8 possessed high performances in gas sorption and especially for CO_2 separation.     

Catalytic Asymmetric Friedel–Crafts Alkylation of Indole via In Situ Generated Indol-2-one

An asymmetric Friedel–Crafts alkylation of indole with in situ generated indol-2-one from functionalized 3-bromooxinidole catalyzed by chiral N,N’-dioxide/Ni(BF₄)₂ has been developed. This protocol provides an efficient route to stereoselective construction of a series of 3-substituted 3’-indolyloxindoles bearing a quaternary carbon center in excellent yields and enantioselectivities (up to 99 % ee). In addition, the conversion of the resulted 3-substituted 3’-indolyloxindole to the key intermediate for the formal synthesis of (+)-folicanthine was also demonstrated.     

Metal Triflate–Catalyzed Friedel–Crafts Acetylation of 3-Phenylsydnone

Friedel–Crafts acetylation at the 4-position of 3-phenylsydnone (1) was achieved via thermal heating overnight in moderate to good yields by employing various metal triflate catalysts (5–20 mol%), lithium perchlorate (0–20 mol%), and acetic anhydride (4 equivalents) using either acetonitrile or acetic anhydride, in excess, as solvent. Six commercially available, homogeneous metal triflate catalysts were investigated, and optimal conditions were determined. The best yields overall were achieved with indium triflate.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications ^® to view the free supplemental file.     

Formal meta-specific intramolecular Friedel–Crafts allylic alkylation of phenols through a spirocyclization–dienone–phenol rearrangement cascade

Formal meta-specific intramolecular Friedel–Crafts allylic alkylation of phenols was achieved based on spirocyclization–dienone–phenol rearrangement cascades. Systematic screening of acid catalysts revealed that Sc(OTf)₃ was a highly effective catalyst for dienone–phenol rearrangement of spiro[4.5]cyclohexadienones. Using 5 mol % of Sc(OTf)₃ as the promoter, various spirocyclic substrates were transformed into the corresponding phenol derivatives in good to excellent yield. Furthermore, the one-pot sequential spirocyclization–dienone–phenol rearrangement proceeded using a palladium and scandium multi-catalytic system or a triphenylmethyl cation single-catalyst system, providing the corresponding meta-allylated phenol derivatives in excellent yield.     

Synthesis of PhTAD-substituted dihydropyrrole derivatives via stereospecific C–H amination

Research on Chemical Intermediates - Stereospecific α-amination has been accomplished via addition of N-phenyltriazolinedione (PhTAD) to the allylic position of dihydropyrroles. The aim of...     

Synthesis of tetracyclic indoles via intramolecular α-arylation of ketones

An intramolecular palladium(0)-mediated α-arylation of ketones applied to the synthesis of various substituted tetracyclic indoles is reported. Most significantly, the efficiency of the transformation was enhanced by the use of monoligated Pd(0) complexes. This methodology was extended to double α-arylation of ketones using one-pot reactions with either simultaneous addition or sequential addition of two aryl halides for producing aryl substituted tetracyclic indoles.