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Selective friedel crafts

Kohei Fuchibe, Hibiki Hatta, Ken Oh, Rie Oki, Junji Ichikawa
Activation of the sp(3) C-F bond in 2-trifluoromethyl-1-alkenes was accomplished through treatment with a Lewis acid. In the presence of an equimolar amount of EtAlCl2 , the (trifluoromethyl)alkenes readily underwent an SN 1'-type reaction with arenes through a Friedel-Crafts-type mechanism via elimination of a fluoride ion to afford 3,3-difluoroallylated arenes in good yields. This selective activation of one C-F bond of the CF3 group provides a synthetic method for accessing biologically and synthetically important 1,1-difluoro-1-alkenes...
April 18, 2017: Angewandte Chemie
Mozhgan Bahrami, Xingwen Zhang, Morteza Ehsani, Yousef Jahani, Richard M Laine
Traditional electrophilic bromination follows long established "rules": electron-withdrawing substituents cause bromination selective for meta positions, whereas electron-donating substituents favor ortho and para bromination. In contrast, in the [PhSiO1.5]8,10,12 silsesquioxanes, the cages act as bulky, electron withdrawing groups equivalent to CF3; yet bromination under mild conditions, without a catalyst, greatly favors ortho substitution. Surprisingly, ICl iodination without a catalyst favors (>90%) para substitution [p-IC6H4SiO1...
March 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Hong-Yu Chen, Meng Gou, Jiao-Bing Wang
Two endo-functionalized organic cages as oxyanion hole mimics were achieved via dynamic covalent chemistry, which exhibit good size selectivity, catalytic activity and broad substrate scopes for Friedel-Crafts reactions. The modular character of the synthesis provides an easy way to modify the size, shape and inner function of the molecular cavity.
March 15, 2017: Chemical Communications: Chem Comm
Jeong-Min Seo, Loon-Seng Tan, Jong-Beom Baek
Popularly utilized oxidation media, via nitric acid/sulfuric acid mixtures, are too corrosive and oxidizing to preserve structural integrity of highly ordered graphitic materials (carbon nanotubes (CNTs) and graphene). Here, for the most commonly used oxidation method, the important advantages of defect/edge-selective functionalization of carbon materials (CNTs/graphene/graphite) in a polyphosphoric acid (PPA)/phosphorous pentoxide (P2 O5 ) medium are elucidated. The optimized PPA/P2 O5 medium is a mild acid that is not only less corrosive than popularly utilized oxidation media, but also has a strong capability to drive Friedel-Crafts acylation by covalently modifying carbon materials...
February 21, 2017: Advanced Materials
Hong-Dong Hao, Dirk Trauner
Two complex norditerpenoids, caribenols A and B, were accessed from a common building block. Our synthesis of caribenol A features the diastereoselective formation of the seven-membered ring through a Friedel-Crafts triflation and a late-stage oxidation of a furan ring. The first synthesis of caribenol B was achieved using an intramolecular organocatalytic α-arylation. An unusual intramolecular aldol addition was developed for the assembly of its cyclopentenone moiety, and the challenging trans-diol moiety was installed through a selective nucleophilic addition to a hydroxy 1,2-diketone...
March 10, 2017: Journal of the American Chemical Society
Christopher A Discolo, Alexander G Graves, Donald R Deardorff
Two complementary strategies have been developed for the C- and O-allylation of phenols via a common π-allyl Pd complex. While O-allylation of phenols by this method is a well-recognized reaction of general utility, the associated para-selective C-allylation reaction is still in its infancy. Cationic π-allyl Pd intermediates, derived from allylic ester carbonates and palladium(0) catalyst, were found to undergo the Friedel-Crafts-type para-selective C-allylations with nine different phenols. Both C- and O-allylated products were obtained in good to excellent yields following a metal-catalyzed regio- and stereospecific substitutive 1,3-transposition...
December 29, 2016: Journal of Organic Chemistry
Hui Gao, Lei Ding, Hua Bai, Lei Li
Hyper-crosslinked polymers (HCPs) are promising materials for gas capture and storage, but high cost and complicated preparation limit their practical application. In this paper, a new type of HCPs (CTHPs) was synthesized through a one-step mild Friedel-Crafts reaction with low-cost coal tar as the starting material. Chloroform was utilized as both solvent and crosslinker to generate a three-dimensional crosslinked network with abundant micropores. The maximum BET surface area of the prepared CTHPs could reach up to 929 m(2)  g(-1) ...
November 24, 2016: ChemSusChem
Partha Samanta, Priyanshu Chandra, Sujit K Ghosh
Two hydroxy-functionalized hyper-cross-linked ultra-microporous compounds have been synthesized by Friedel-Crafts alkylation reaction and characterised with different spectroscopic techniques. Both compounds exhibit an efficient carbon dioxide uptake over other gases like N2, H2 and O2 at room temperature. A high isosteric heat of adsorption (Qst) has been obtained for both materials because of strong interactions between polar -OH groups and CO2 molecules.
2016: Beilstein Journal of Organic Chemistry
Rashid Nazir, Anton J Stasyuk, Daniel T Gryko
A regioselective synthesis of naphtho[2,1,8-def]coumarins has been realized through a concise route that involves the intramolecular Friedel-Crafts reaction of benzo[f]coumarins. Tetracyclic, planar products were prepared starting from assembly of the suitably substituted coumarin via the Pechmann reaction of 2-naphthols with acetone-1,3-dicarboxylates, followed by an intramolecular Friedel-Crafts reaction. In contrast to earlier report, the main product of the condensation reaction performed at 130 °C was the corresponding sulfonic acid and not the phenol itself...
November 18, 2016: Journal of Organic Chemistry
Yingcheng Wang, Liang Jiang, Long Li, Jun Dai, Dan Xiong, Zhihui Shao
The first arylation strategy for the synthesis of enantioenriched propargylamines is disclosed. This approach, which is complementary to previous alkynylation and alkylation strategies, involves a C(sp(2) )-C(sp(3) ) bond formation, and is based on the first asymmetric Friedel-Crafts-type arylation reaction of C-alkynyl imines. Asymmetric Friedel-Crafts reactions with electron-deficient phenols, a longstanding unsolved challenge, have thus been realized for the first time, enabled by the combination of our recently introduced C-alkynyl N-Boc-protected N,O-acetals as electrophiles and chiral phosphoric acids as catalysts...
October 27, 2016: Angewandte Chemie
Rosemary A Croft, James J Mousseau, Chulho Choi, James A Bull
The first examples of 3,3-diaryloxetanes are prepared in a lithium-catalyzed and substrate dependent divergent Friedel-Crafts reaction. para-Selective Friedel-Crafts reactions of phenols using oxetan-3-ols afford 3,3-diaryloxetanes by displacement of the hydroxy group. These constitute new isosteres for benzophenones and diarylmethanes. Conversely, ortho-selective Friedel-Crafts reactions of phenols afford 3-aryl-3-hydroxymethyl-dihydrobenzofurans by tandem alkylation-ring-opening reactions; the outcome of the reaction diverging to structurally distinct products dependent on the substrate regioselectivity...
November 2, 2016: Chemistry: a European Journal
Raphaël Lafleur-Lambert, John Boukouvalas
The first enantioselective synthesis of the fungal metabolite (+)-O-methylasparvenone was achieved in eight steps and 22% overall yield from inexpensive 3,4,5-trimethoxybenzaldehyde dimethyl acetal. Key steps include (i) early-stage asymmetric alkynylation of an aromatic aldehyde with a propiolate, (ii) intramolecular Friedel-Crafts acylation, and (iii) site-selective cleavage of an aryl methyl ether.
September 21, 2016: Organic & Biomolecular Chemistry
Simona Musella, Veronica di Sarno, Tania Ciaglia, Marina Sala, Antonia Spensiero, Maria Carmina Scala, Carmine Ostacolo, Graciela Andrei, Jan Balzarini, Robert Snoeck, Ettore Novellino, Pietro Campiglia, Alessia Bertamino, Isabel M Gomez-Monterrey
We report the synthesis and antiviral activity of a new family of non-nucleoside antivirals, derived from the indole nucleus. Modifications of this template through Mannich and Friedel-Crafts reactions, coupled with nucleophilic displacement and reductive aminations led to 23 final derivatives, which were pharmacologically tested. Tryptamine derivative 17a was found to have a selective inhibitory activity against human varicella zoster virus (VZV) replication in vitro, being inactive against a variety of other DNA and RNA viruses...
November 29, 2016: European Journal of Medicinal Chemistry
Kamalkishore Pati, Gabriel Dos Passos Gomes, Igor V Alabugin
This work discloses the first general solution for converting oligoalkynes into polyaromatic polycyclic systems free of pentagonal defects. The efficiency and selectivity of this cascade originate from the combination of the Bu3 Sn-mediated TDG (traceless directing group) cascade transformations of skipped alkynes where the reactivity of the key radical precursor is tempered by hybridization effects. This approach ensures that the final structure consists of only six-membered rings. Practical implementation of this strategy is readily accomplished by incorporation of a suitably-substituted alkene as a final unit in the domino transformation...
September 12, 2016: Angewandte Chemie
Yoichiro Kuninobu, Mitsumi Nishi, Motomu Kanai
We developed a copper-catalyzed 5-position-selective C-H trifluoromethylation of 8-aminoquinoline derivatives. The reaction proceeded with high functional group tolerance under mild conditions. In the case of quinolines with an amide, carbamate, urea, or sulfonamide group at the 8-position of quinoline moieties, a radical scavenger experiment indicated that the reaction proceeded via a radical pathway. The protecting group of an 8-amidoquinoline derivative could be removed by hydrolysis. On the other hand, the trifluoromethylation of 8-aminoquinolines was also promoted by other Lewis acids as well as a copper catalyst and proceeded even in the presence of a radical scavenger...
September 14, 2016: Organic & Biomolecular Chemistry
Edward Richmond, Ismat Ullah Khan, Joseph Moran
A pair of mechanistically divergent multicatalytic reaction sequences has been developed consisting of nickel-catalyzed isomerization of N-allylcarbamates and subsequent phosphoric-acid-catalyzed enantioselective functionalization of the resulting intermediates. By appropriate selection of reaction partners, in situ generated imines and ene-carbamates are mechanistically partitioned to yield opposing functionalized products. Formal α-functionalization to give protected α-arylamines is achieved upon enantioselective Friedel-Crafts reaction with arene nucleophiles, whereas formal β-functionalization is achieved upon reaction with diarylimine electrophiles in an enantioselective Povarov-[4+2] cycloaddition...
August 22, 2016: Chemistry: a European Journal
Trinadh Kaicharla, Tony Roy, Manikandan Thangaraj, Rajesh G Gonnade, Akkattu T Biju
Lewis acid-catalyzed reactions of 2-substituted cyclopropane 1,1-dicarboxylates with 2-naphthols is reported. The reaction exhibits tunable selectivity depending on the nature of Lewis acid employed and proceed as a dearomatization/rearomatization sequence. With Bi(OTf)3 as the Lewis acid, a highly selective dehydrative [3+2] cyclopentannulation takes place leading to the formation of naphthalene-fused cyclopentanes. Interestingly, engaging Sc(OTf)3 as the Lewis acid, a Friedel-Crafts-type addition of 2-naphthols to cyclopropanes takes place, thus affording functionalized 2-naphthols...
August 16, 2016: Angewandte Chemie
Mengistu Gemech Menkir, Shyi-Long Lee
The mechanism and regioselectivity of the intramolecular hydroarylation of phenyl propargyl ether catalyzed by indium in gas and solvent phases were investigated by means of the density functional theory method. The computed results revealed that the reaction proceeds through initial π-coordination of the propargyl moiety to the catalyst, which triggers the nucleophilic attack of the phenyl ring via an exo- or endo-dig pathway in a Friedel-Crafts type mechanism. Calculation results obtained employing InI2(+) as the possible catalyst show similar activation energies for the 5-exo-dig and 6-endo-dig pathways...
July 6, 2016: Organic & Biomolecular Chemistry
Wangdong Zeng, Zhe Sun, Tun Seng Herng, Théo P Gonçalves, Tullimilli Y Gopalakrishna, Kuo-Wei Huang, Jun Ding, Jishan Wu
The challenging synthesis of a laterally extended heptazethrene molecule, the super-heptazethrene derivative SHZ-CF3, is reported. This molecule was prepared using a strategy involving a multiple selective intramolecular Friedel-Crafts alkylation followed by oxidative dehydrogenation. Compound SHZ-CF3 exhibits an open-shell singlet diradical ground state with a much larger diradical character compared with the heptazethrene derivatives. An intermediate dibenzo-terrylene SHZ-2H was also obtained during the synthesis...
July 18, 2016: Angewandte Chemie
Yongmei Liu, Guangrong Meng, Ruzhang Liu, Michal Szostak
Highly chemoselective Friedel-Crafts acylation with twisted amides under mild conditions is reported for the first time. The reaction shows high functional group tolerance, obviating the need for preformed sensitive organometallic reagents and expensive transition metal catalysts. The high reactivity of amides is switched on by ground-state steric distortion to disrupt the amide bond nN→πCO* resonance as a critical design feature. Conceptually, this new acid-promoted mechanism of twisted amides provides direct access to bench-stable acylating reagents under mild, metal-free conditions...
May 21, 2016: Chemical Communications: Chem Comm
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