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Selective friedel crafts

Jianrong Steve Zhou, Zhiwei Jiao, Li Hui Lim, Hajime Hirao
Intermolecular alkylation of electron-deficient arenes proceeds with good para selectivity to electron-withdrawing groups. Palladium catalysts are used to generate nucleophilic alkyl radicals from alkyl halides, which add onto arenes directly. Its scope of arenes and site of alkylation of are opposite to those of classical Friedel-Crafts alkylation, which prefers electron-rich rings and electron-rich sites.
April 12, 2018: Angewandte Chemie
Yini Zuo, Na Yang, Xunkun Huang, Changwei Hu, Zhishan Su
The mechanism and selectivity of asymmetric Friedel-Crafts (F-C) alkylation reaction between indole and chalcone catalyzed by chiral N, N'-dioxide-Sc(III) complexes were investigated at the M06/6-311+G(d,p)//M06/[LANL2DZ, 6-31G(d)](SMD,CH2Cl2) level. The reaction occurred via a three-step mechanism: (i) the C3-C bond formation by interacting the most mucleophilic C3 centre of indole with the most electrophilic C centre of chalcone; (ii) the abstraction of the proton at C3 atom of indole by counterion OTf-; (iii) proton transfer from HOTf to C atom of chalcone, generating F-C alkylation product...
March 30, 2018: Journal of Organic Chemistry
Jiahui Kou, Lin-Bing Sun
Due to their diverse structure, high porosity, and tunable functionality, metal-organic frameworks (MOFs) are of great inter-est for diverse applications including catalysis. However, the poor hydrostability of most reported MOFs hinders their cata-lytic applications seriously. In addition, the development of an effective method to improve the catalytic activity of MOFs is another challenge. Here, we report for the first time the development of a double-solvent strategy to fabricate MOFs inside silica nanopores...
March 14, 2018: ACS Applied Materials & Interfaces
Jie Liu, Zhihong Wei, Haijun Jiao, Ralf Jackstell, Matthias Beller
Green Friedel-Crafts acylation reactions belong to the most desired transformations in organic chemistry. The resulting ketones constitute important intermediates, building blocks, and functional molecules in organic synthesis as well as for the chemical industry. Over the past 60 years, advances in this topic have focused on how to make this reaction more economically and environmentally friendly by using green acylating conditions, such as stoichiometric acylations and catalytic homogeneous and heterogeneous acylations...
January 24, 2018: ACS Central Science
R Garrison Kinney, Jevgenijs Tjutrins, Gerardo M Torres, Nina Jiabao Liu, Omkar Kulkarni, Bruce A Arndtsen
The development of metal-catalysed methods to functionalize inert C-H bonds has become a dominant research theme in the past decade as an approach to efficient synthesis. However, the incorporation of carbon monoxide into such reactions to form valuable ketones has to date proved a challenge, despite its potential as a straightforward and green alternative to Friedel-Crafts reactions. Here we describe a new approach to palladium-catalysed C-H bond functionalization in which carbon monoxide is used to drive the generation of high-energy electrophiles...
February 2018: Nature Chemistry
Matthew R Porter, Rami M Shaker, Cristian Calcanas, Joseph J Topczewski
This report describes the stereoselective synthesis of 3-azido-tetralins, -chromanes, and -tetrahydroquinolines via a tandem allylic azide rearrangement/Friedel-Crafts alkylation. Exposure of allylic azides with a pendant trichloroacetimidate to catalytic quantities of AgSbF6 proved optimal for this transformation. This cascade successfully differentiates the equilibrating azide isomers, providing products in excellent yield and selectivity (>25 examples, up to 94% yield and >25:1 dr). In many cases, the reactive isomer is only a trace fraction of the equilibrium mixture, keenly illustrating the dynamic nature of these systems...
January 31, 2018: Journal of the American Chemical Society
Siduo Wu, Chao Teng, Sheng Cai, Biwang Jiang, Yong Wang, Hong Meng, Huchun Tao
A novel triphenylphosphine-based porous polymer (TPDB) with a high Brunauer-Emmett-Teller (BET) surface area was synthesized through Friedel-Crafts alkylation of triphenylphosphine and α-dibromo-p-xylene. Then, the functional hydroxyl groups were successfully grafted onto the polymer framework by post modification of TPDB with 3-bromo-1-propanol (BP) and triethanolamine (TEA). The resulting sample TPDB-BP-TEA was characterized by various techniques such as FT-IR, TG, SEM, EDS mapping, ICP-MS, and N2 adsorption-desorption...
November 28, 2017: Nanoscale Research Letters
Lishu Shao, Mingqiang Liu, Jianhan Huang, You-Nian Liu
The N-containing hyper-cross-linked polymers with different porosity and polarity were prepared from 4-vinylbenzyl chloride and 4-vinyl pyridine by the suspension polymerization and Friedel-Crafts reaction. A carbonization process by KOH chemical activation was carried out for the N-containing hyper-cross-linked polymers, and hence a series of N-doped porous carbons (NDPC) was easily fabricated. These porous materials were comparatively evaluated for CO2 adsorption. The NDPC were much more efficient than the N-containing hyper-cross-linked polymers for the CO2 capture and the CO2 uptake had a linear correlation to the ultramicropore volume (d ≤ 0...
November 15, 2017: Journal of Colloid and Interface Science
Min Liu, Xue Chen, Tieqiao Chen, Qing Xu, Shuang-Feng Yin
A selective oxidative para-acylation of unprotected anilines with methyl groups in N-heteroarylmethanes was achieved. This transformation proceeds under mild metal-free reaction conditions to produce the corresponding valuable diarylmethanones in good to high yields, featuring high site-selectivity, high functional-group-tolerance, gram-scale synthesis and easy product-derivation. Preliminary mechanistic studies revealed that the present oxidative para-acylation would take place via a Friedel-Crafts-type process of in situ imines and the steric hindrance might be the key issue for the high regio-selectivity...
November 29, 2017: Organic & Biomolecular Chemistry
Lu Ye, Sai-Hu Cai, Ding-Xing Wang, Yi-Qiu Wang, Lin-Jie Lai, Chao Feng, Teck-Peng Loh
A visible-light-engaged 2-fold site-selective alkylation of indole derivatives with aliphatic ethers or alcohols has been accomplished for easy access to symmetric 3,3'-bisindolylmethane derivatives. The experimental data suggest a sequential photoredox catalysis induced radical addition and proton-mediated Friedel-Crafts alkylation mechanism.
November 17, 2017: Organic Letters
Xiaotian Qi, Yingzi Li, Ruopeng Bai, Yu Lan
Transition-metal-catalyzed cross-coupling has emerged as an effective strategy for chemical synthesis. Within this area, direct C-H bond transformation is one of the most efficient and environmentally friendly processes for the construction of new C-C or C-heteroatom bonds. Over the past decades, rhodium-catalyzed C-H functionalization has attracted considerable attention because of the versatility and wide use of rhodium catalysts in chemistry. A series of C-X (X = C, N, or O) bond formation reactions could be realized from corresponding C-H bonds using rhodium catalysts...
November 7, 2017: Accounts of Chemical Research
Wei Yu, Minghong Zhou, Tianqi Wang, Zidong He, Buyin Shi, Yang Xu, Kun Huang
The synthesis of azide functional microporous organic nanotube networks (N3-MONNs) via a Friedel-Crafts hyper-cross-linking reaction is reported. Subsequently, a general method for obtaining heterogeneous catalysts through a Cu-catalyzed alkyne-azide reaction is presented. The small-molecule catalysts such as 2,2,6,6,-tetramethylpiperidine-1-oyl and 4-(N,N-dimethylamino)pyridine can be anchored into the MONNs. Owing to the hierarchically porous structure and high surface area, these catalysts show high activity in selective oxidation of alcohols and acylation reaction, respectively...
October 26, 2017: Organic Letters
Jaya Kishore Vandavasi, XiYe Hua, Hamdi Ben Halima, Stephen G Newman
The use of transition-metal catalysis to enable the coupling of readily available organic molecules has greatly enhanced the ability of chemists to access complex chemical structures. In this work, an intermolecular coupling reaction that unites organotriflates and aldehydes is presented. A unique catalyst system is identified to enable this reaction, featuring a Ni(0) precatalyst, a tridentate Triphos ligand, and a bulky amine base. This transformation provides access to a variety of ketone-containing products without the selectivity- and reactivity-related challenges associated with more traditional Friedel-Crafts reactions...
October 18, 2017: Angewandte Chemie
Heemal H Dhanjee, Yutaka Kobayashi, Jonas F Buergler, Travis C McMahon, Matthew W Haley, Jennifer M Howell, Koichi Fujiwara, John L Wood
Described herein are syntheses of the naturally occurring polyketides (-)-tetrapetalones A and C and their respective enantiomers. The employed strategy involves initial assembly of a masked N-aryl tetramic acid which is advanced via a highly selective conjugate addition/intramolecular Friedel-Crafts acylation sequence to deliver a key azepine intermediate. Application of recently developed C-H activation chemistry and subsequent Heck cyclization delivers the aglycone framework in an overall 12 steps. Resolution of the aglycone via stereospecific glycosylation with an enantiopure glycosyl donor followed by separation of the derived diastereomers enables further advancement to either (+)- or (-)-tetrapetalones A and C...
October 11, 2017: Journal of the American Chemical Society
Zhengbao Xu, Li Chai, Zhong-Quan Liu
A free-radical-promoted aryl/heteroaryl C-H silylation using hydrosilane was developed. This cross-dehydrogenative silylation enables both electron-rich and electron-poor aromatics to afford the desired arylsilanes in unique selectivity. A "para-selectivity" was observed by examination of over 54 examples. This exceptional orientation is quite different from that in Friedel-Crafts C-H silylation or transition-metal-catalyzed dehydrogenative silylation.
September 29, 2017: Organic Letters
Minami Odagi, Yoshiharu Yamamoto, Kazuo Nagasawa
The enantioselective total synthesis of (+)-gracilamine (1) is described. The strategy features a diastereoselective phenolic coupling reaction followed by a regioselective intramolecular aza-Michael reaction to construct the ABCE ring system. The configuration at C3a in 1 was controlled by the stereocenter at C9a, which was selectively generated (91 % ee) by an organocatalytic enantioselective aza-Friedel-Crafts reaction developed by our research group. This synthesis revealed that the absolute configuration of (+)-gracilamine is 3aR, 4S, 5S, 6R, 7aS, 8R, 9aS...
September 19, 2017: Angewandte Chemie
Susann Rath, Dirk Schepmann, Bernhard Wünsch
Since overactivation of NMDA receptors is associated with neurodegenerative disorders, the design and development of subunit-selective NMDA receptor antagonists are of great interest. In order to avoid the formation of quinone-like intermediates as starting point for degradation the benzylic OH group of the lead compounds 2 was replaced by an electron rich vinyl or homologous hydroxymethyl moiety. The Bi(OTf)3 catalyzed intramolecular Friedel-Crafts alkylation of 9a represents the key step in the synthesis of 1-vinyl substituted tetrahydro-3-benzazepine 10...
October 15, 2017: Bioorganic & Medicinal Chemistry
Ziyan Jia, Jiannan Pan, Daqiang Yuan
By introducing various N-containing compounds as efficient linkers, a series of hyper-crosslinked porous polymers with high surface areas and gas-uptake values were synthesized by using the Friedel-Crafts alkylation reaction. Structural characterization indicated the presence of nitrogen atoms, and gas-sorption experiments revealed that the high gas uptake benefitted from the high surface areas and the incorporation of N-containing linkers as Lewis basic sites. Among these porous polymers, HCP-4 had the highest H2 uptake of 9...
August 2017: ChemistryOpen
Ting Zhang, Jianhan Huang
The polar modified hyper-cross-linked resins were synthesized by the suspension polymerization and Friedel-Crafts alkylation reaction, and the effect of the feeding amount of the monomers (N-vinylimidazole and p-vinylbenzyl chloride) on the porosity and polarity were clarified. As the feeding amount of p-vinylbenzyl chloride decreased from 75% to 50% (w/w), the Brunauer-Emmett-Teller surface area of the resins lowered from 1306 to 436 m(2)/g, and the pore size distribution showed a large population of pores in micropores stretching to a higher percentage of mesopores...
November 1, 2017: Journal of Colloid and Interface Science
Nina G Schmidt, Tea Pavkov-Keller, Nina Richter, Birgit Wiltschi, Karl Gruber, Wolfgang Kroutil
The Friedel-Crafts acylation is commonly used for the synthesis of aryl ketones, and a biocatalytic version, which may benefit from the chemo- and regioselectivity of enzymes, has not yet been introduced. Described here is a bacterial acyltransferase which can catalyze Friedel-Crafts C-acylation of phenolic substrates in buffer without the need of CoA-activated reagents. Conversions reach up to >99 %, and various C- or O-acyl donors, such as DAPG or isopropenyl acetate, are accepted by this enzyme. Furthermore the enzyme enables a Fries rearrangement-like reaction of resorcinol derivatives...
June 19, 2017: Angewandte Chemie
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