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Selective friedel crafts

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...
September 7, 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
Carolina García-García, Laura Ortiz-Rojano, Susana Álvarez, Rosana Álvarez, María Ribagorda, M Carmen Carreño
Lewis acid catalyzed Friedel-Crafts alkylation of indoles has been achieved in high yields and selectivities using p-quinols as electrophiles. (S)-Binol-3,3'-(9-anthracenyl)-phosphoric acid was able to catalyze the enantioselective formation of 5-(3-indole)-2-cyclohexenone derivatives. Experimental results and theoretical calculations explained the enantioselectivity based on a transition state where two water molecules act as a tether joining the p-quinol with the phosphoric acid and the NH of indole, thus facilitating the desymmetrization of the prochiral cyclohexadienone framework...
May 6, 2016: Organic Letters
Ma Chen-Chen, Zhao-Peng Liu
A variety of coumarin derivatives possessing the pyridinylurea units were designed to increase their potency and isoform selectivity against PI3Ks. These novel coumarins 4a-m were prepared from 5-methyl-pyridin-2-ylamine in a straightforward way via the protection of the amino by Boc groups, benzyl bromination, ethyl acetoacetate alkylation with the generated bromomethyl pyridine, Pechmann coumarin core construction, and ureas formation by the coupling of amine 3 with a variety of aryl isocyanates. When the alkylated acetoacetate 2 was reacted with resorcinol in concentrated sulfuric acid, a cascade reaction occurred that included the Pechmann cyclization to form the coumarin core, removal of the N-Boc protective groups to generate a tert-butyl carbocation, and the Friedel-Crafts tert-butylation of the phenol ring...
February 23, 2016: Anti-cancer Agents in Medicinal Chemistry
Denan Sun, Bijin Li, Jingbo Lan, Quan Huang, Jingsong You
Pd-Catalysed ortho-selective oxidative C-H/C-H cross-coupling of aromatic carboxylic acids with arenes and subsequent intramolecular Friedel-Crafts acylation has been accomplished for the first time through a chelation-assisted C-H activation strategy. Starting from the readily available substrates, a variety of fluorenone derivatives are obtained in one pot. The direct use of naturally occurring carboxylic acid functionalities as directing groups avoids unnecessary steps for installation and removal of an extra directing group...
March 4, 2016: Chemical Communications: Chem Comm
Gangaram Pallikonda, Manab Chakravartya
Easily reachable electron-poor/rich primary and secondary benzylic phosphates are suitably used as substrates for Friedel-Crafts benzylation reactions with only 1.2 equiv activated/deactivated arenes (no additional solvent) to access structurally and electronically diverse polyarylated alkanes with excellent yields and selectivities at room temperature. Specifically, diversely substituted di/triarylmethanes are generated within 2-30 min using this approach. A wide number of electron-poor polyarylated alkanes are easily accomplished through this route by just tuning the phosphates...
March 4, 2016: Journal of Organic Chemistry
Marek Grzybowski, Artur Jeżewski, Irena Deperasińska, Daniel H Friese, Marzena Banasiewicz, Vincent Hugues, Bolesław Kozankiewicz, Mireille Blanchard-Desce, Daniel T Gryko
A novel non-centrosymmetric π-expanded diketopyrrolopyrrole was designed and synthesized. Strategic placement of tert-butyl groups at the periphery of a diketopyrrolopyrrole allowed us to selectively fuse one moiety via tandem Friedel-Crafts-dehydration reactions, resulting in a non-centrosymmetric dye. The structure of the dye was confirmed by X-ray crystallography, revealing that it contains a nearly flat arrangement of four fused rings. Extensive photophysical studies of this new functional dye revealed that the intensity of its emission strongly depends on solvent polarity, which is typical for dipolar chromophores...
February 14, 2016: Organic & Biomolecular Chemistry
B V Subba Reddy, A Venkateswarlu, B Sridevi, Salem S Aldeyab, Ajayan Vinu
Friedel-Crafts alkylation of electron-rich arenes with aldehydes has been achieved in the presence of an active and selective Amberlyst-15 catalyst at the reaction temperature of 60 degrees C in solvent-free conditions. The catalyst exhibits a very high activity and offers the corresponding triarylmethanes in excellent yields with a high selectivity. The use of highly reactive and selective Amberlyist-15 makes this procedure simple, convenient, cost-effective, practical and environmentally friendly. This method provides an easy access to triarylmethanes in a single step using a readily available acidic ionic resin, which is a stable and easy to separate from the reaction mixture by a simple filtration technique...
September 2015: Journal of Nanoscience and Nanotechnology
B V Subba Reddy, Y Vikram Reddy, Kiran Kumar Singarapu
2-Furylcarbinols undergo a smooth aza-Piancatelli rearrangement followed by Friedel-Crafts alkylation with a bifunctional substrate, (1H-pyrrol-1-yl)aniline, in the presence of 10 mol% In(OTf)3 in acetonitrile at room temperature to afford the corresponding hexahydrobenzo[b]cyclopenta[f]pyrrolo[1,2-d][1,4]diazepin-11(4aH)-one scaffolds in good yields. This method offers significant advantages such as high conversions, mild reaction conditions, short reaction times, and high selectivity. The relative stereochemistry of the product was established by nOe studies...
January 21, 2016: Organic & Biomolecular Chemistry
Giacomo E M Crisenza, Olga O Sokolova, John F Bower
An iridium(I) catalyst system, modified with the wide-bite-angle and electron-deficient bisphosphine d(F) ppb (1,4-bis(di(pentafluorophenyl)phosphino)butane) promotes highly branch-selective hydroarylation reactions between diverse acetanilides and aryl- or alkyl-substituted alkenes. This provides direct and ortho-selective access to synthetically challenging anilines, and addresses long-standing issues associated with related Friedel-Crafts alkylations.
December 1, 2015: Angewandte Chemie
Eric M Phillips, Tehetena Mesganaw, Ashay Patel, Simon Duttwyler, Brandon Q Mercado, Kendall N Houk, Jonathan A Ellman
The asymmetric synthesis of ent-ketorfanol from simple and commercially available precursors is reported. A Rh(I) -catalyzed intramolecular CH alkenylation/torquoselective 6π electrocyclization cascade provides a fused bicyclic 1,2-dihydropyridine as a key intermediate. Computational studies were performed to understand the high torquoselectivity of the key 6π electrocyclization. The computational results demonstrate that a conformational effect is responsible for the observed selectivity. The ketone functionality and final ring are introduced in a single step by a redox-neutral acid-catalyzed rearrangement of a vicinal diol to give the requisite carbonyl, followed by intramolecular Friedel-Crafts alkylation...
October 5, 2015: Angewandte Chemie
Congfa He, Jie Wang, Zhenhua Gu
A BF3·OEt2-promoted cyclization of metallocenyl enones to form cyclohexanone-fused metallocenes is reported. 2,3-Metallocenocyclohexanones were formed exclusively, and no normal Nazarov-type cyclopentanone analogues were detected. The reaction possibly proceeded via an unusual cationic 1,2-hydride shift followed by Friedel-Crafts alkylative cyclization process. During the studies of the alkylation reaction of these keto esters, an unusual and rare facial selectivity was observed. The electrophiles would be attacked from the same face as the second Cp ring...
August 21, 2015: Journal of Organic Chemistry
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