Friedel‐Crafts Alkylation of Indoles with Nitroalkenes Catalyzed by Zn(II)‐Thiourea Complex

Friedel‐Crafts alkylation of indoles with nitroalkenes catalyzed by a novel Zn(II)‐thiourea complex has been developed. The remarkable advantages of this reaction are mild reaction conditions, simple workup procedure, high yield of products and the use of ethanol as acceptable solvent.     

Direct C-H arylation of (hetero)arenes with aryl iodides via rhodium catalysis

A new method for the catalytic C-H arylation of heteroarenes and arenes that manifests high activity paired with reasonably broad scope was developed. Under the catalytic influence of RhCl(CO){P[OCH(CF3)2]3}2 and Ag2CO3, the direct C-H arylation of heteroarenes/arenes with aryl/heteroaryl iodides took place to afford a range of biaryls in good to excellent yields with high regioselectivity. Thiophenes, furans, pyrroles, indoles, and alkoxybenzenes are applicable in this arylation protocol.     

Photocrosslinked poly(vinylbenzophenone)‐core micelles via mild Friedel–Crafts benzoylation of polystyrene amphiphiles

Photocrosslinkable poly(vinylbenzophenone)‐containing polymers were synthesized via a one‐step, Friedel–Crafts benzoylation of polystyrene‐containing starting materials [including polystyrene, polystyrene‐block‐poly(tert‐butyl acrylate), polystyrene‐block‐poly(ethylene oxide), polystyrene‐block‐poly(methyl methacrylate), and polystyrene‐block‐poly(n‐butyl acrylate)] with benzoyl trifluoromethanesulfonate as a benzoylation reagent. The use of this mild reagent (which required no added Lewis acid) permitted polymers with well‐defined compositions and narrow molecular weight distributions to be synthesized. Micelles formed from one of these benzoylated polymers, [polystyrene_0.25‐co‐poly(vinylbenzophenone)_0.75]₁₁₅‐block‐poly(acrylic acid)₁₄, were then fixed by the irradiation of the micelle cores with UV light. As the irradiation time was increased, the pendent benzophenone groups crosslinked with other chains in the glassy micelle cores. Dynamic light scattering, spectrofluorimetry, and Fourier transform infrared spectroscopy were all used to verify the progress of the crosslinking reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2604–2614, 2006     

A facile synthesis of dihydrobenzofuranols by photocyclization of (2‐alkoxy‐5‐methyl‐phenyl)(aryl) methanone and ethyl 2‐aroyl‐4‐methylphenyloxyacetates

Irradiation of 2‐alkoxy substituted benzophenones 2a–f and ethyl 2‐aroyl‐4‐methylphenyloxyacetates 2g–i in benzene and in acetonitrile underwent photocyclization to substituted dihydrobenzofuranols 3a–i with 3a–c in very less yield being racemate and 3d–i in good yield being mixture of cis‐trans isomers showing high stereoselectivity in benzene and decreased stereoselectivity in acetonitrile. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:212–217, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20111     

Superacid‐catalyzed Friedel–Crafts phosphination of 2‐hydroxybiphenyls with phosphorus trichloride

Cyclic phosphorus compounds, 6H‐dibenz[c,e][1,2]oxaphosphorin‐6‐oxide derivatives, were efficiently synthesized by the Friedel–Crafts reaction of 2‐hydroxybiphenyls with phosphorus trichloride in the presence of superacids, especially trifluoromethanesulfonic acid (TfOH) as a catalyst. TfOH was investigated for the first time as an effective catalyst for the aromatic phosphination of 2‐hydroxybiphenyls.     

Friedel–Crafts Alkylation of N‐(2‐Chloropropionyl)aniline and the Generation Mechanism of Byproducts

The cyclization of N‐(2‐chloropropionyl)aniline to 3‐methylindolin‐2‐one through Friedel–Crafts alkylation was studied. It was found that N‐phenylacrylamide (12.6%) and 3,4‐dihydro‐2(1H)‐quinolinone (1.5%) as main byproducts were obtained. On the basis of the mechanism of Friedel–Crafts alkylation, the generation mechanisms of these two compounds were proposed.     

Synthesis of poly(aryl ether ketone)s containing diphenyl moieties by electrophilic Friedel–Crafts solution polycondensation

A new monomer, 4,4′‐bis(4‐phenoxybenzoyl)diphenyl (BPOBDP), was prepared by Friedel–Crafts reaction of 4‐bromobenzoyl chloride and diphenyl, followed by condensation with potassium phenoxide. Novel poly(ether ketone ketone) (PEKK)/poly(ether ketone diphenyl ketone ether ketone ketone) (PEKDKEKK) copolymers were synthesized by electrophilic Friedel–Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of diphenyl ether (DPE) and BPOBDP, in the presence of anhydrous aluminum chloride and N‐methyl‐pyrrolidone (NMP) in 1,2‐dichloroethane (DCE). The copolymers obtained were characterized by various analytical techniques such as FT‐IR, DSC, TGA, and wide‐angle X‐ray diffraction (WAXD). The results showed that the resulting copolymers exhibited excellent thermal stability due to the existence of diphenyl moieties in the main chain. The glass transition temperatures are above 152°C, the melting temperatures are above 276°C, and the temperatures at a 5% weight loss are above 548°C in nitrogen. The copolymers with 50–70 mol% BPOBDP had tensile strengths of 101.5–102.7 MPa, Young's moduli of 3.23–3.41 GPa, and elongations at break of 12–17%. All these copolymers were semicrystalline and insoluble in organic solvents. Copyright © 2008 John Wiley & Sons, Ltd.     

Aluminium Chloride‐Catalyzed Intermolecular vs Intramolecular Friedel‐Crafts Reaction of Acrylanilides and 3‐Chloropropanamides

3‐Phenylpropionanilide ( 4a ) is obtained in a yield of 89% from acrylanilide by the treatment with AlCl₃/benzene, compared with a yield of 39% by the 1,4‐conjugate addition of phenyllithium. The formation of 4a indicated that an intermolecular Friedel‐Crafts reaction occurred, rather than the relatively more facile intramolecular ring cyclization, and provided a more efficient route than a conjugate addition of phenyllithium for the preparation of 3‐phenylpropionanilide and its derivatives. Although the methoxy group is an activator of the nucleophilic substitution, introduction of a methoxy substituent at N‐phenyl did not increase the competitive capability of the intramolecular cyclization because of AlCl₃‐catalyzed demethylation to form the ArOAlCl₂ complex which decreased the availability of the π‐electron in the N‐phenyl aromatic system.     

9‐Membered Carbocycle Formation: Development of Distinct Friedel–Crafts Cyclizations and Application to a Scalable Total Synthesis of (±)‐Caraphenol A

Explorations into a series of different approaches for 9‐membered carbocycle formation have afforded the first reported example of a 9‐exo‐dig ring closure via a Au^III‐promoted reaction between an alkyne and an aryl ring as well as several additional, unique Friedel–Crafts‐type cyclizations. Analyses of the factors leading to the success of these transformations are provided, with the application of one of the developed 9‐membered ring closures affording an efficient and scalable synthesis of the bioactive resveratrol trimer caraphenol A. That synthesis proceeded with an average yield of 89 % per step (7.8 % overall yield) and has provided access to more than 600 mg of the target molecule.     

Organocatalytic Asymmetric Friedel–Crafts Reaction of Sesamol with Isatins: Access to Biologically Relevant 3‐Aryl‐3‐hydroxy‐2‐oxindoles

The Friedel–Crafts reaction of electron‐rich phenols with isatins was developed by employing bifunctional thiourea–tertiary amine organocatalysts. Cinchona alkaloid derived thiourea epiCDT‐ 3 a efficiently catalyzed the Friedel–Crafts‐type addition of phenols to isatin derivatives to provide 3‐aryl‐3‐hydroxy‐2‐oxindoles 7 and 9 in good yield (80–95 %) with good enantiomeric excess (83–94 %). Friedel–Crafts adduct 7 t was subjected to a copper(I)‐catalyzed azide–alkyne cycloaddition to obtain biologically important 3‐aryl‐3‐hydroxy‐2‐oxindole 11 in good enantiomeric excess and having a 1,2,3‐triazole moiety.     

A Highly Efficient Friedel–Crafts Reaction of 3‐Hydroxyoxindoles and Aromatic Compounds to 3,3‐Diaryl and 3‐Alkyl‐3‐aryloxindoles Catalyzed by Hg(ClO4)2⋅3 H2O

We report a highly efficient Friedel–Crafts reaction of 3‐alkyl or 3‐aryl 3‐hydroxyoxindoles with a variety of aromatic and heteroaromatic compounds to unsymmetrical 3,3‐diaryloxindoles or 3‐alkyl‐3‐aryloxindoles, which are interesting medicinal targets and useful building blocks for the synthesis of natural products. Hg(ClO₄)₂ ? 3 H₂O was identified as a powerful catalyst for this reaction, and is significantly more efficient than other screened metal perchlorate hydrates and Brønsted acids such as HOTf and HClO₄. The high catalytic property of Hg(ClO₄)₂ ? 3 H₂O originates from the unprecedented dual activation effects of aromatic mercuration, which could generate a strong protic acid to facilitate the generation of a carbocation at the C3‐position of oxindoles and simultaneously form the more reactive nucleophilic reaction partner.