- Visible-light-mediated alkylation of 4-alkyl-1,4-dihydropyridines with alkenyl sulfones
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Herein we report a mild, general protocol for visible-light-mediated alkylation of 4-alkyl-1,4-dihydropyridines with alkenyl sulfones. The protocol permits efficient functionalization of sulfones with a broad range of cyclic and acyclic secondary and tert
- Dong, Jianyang,Liu, Yuxiu,Wang, Qingmin,Yue, Fuyang
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p. 8924 - 8928
(2021/11/04)
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- RETRACTED ARTICLE: Copper-Catalyzed Decarboxylative C(sp2)-C(sp3) and C(sp)-C(sp3) Coupling of Substituted Cinnamic Acids and 3-Phenyl Propiolic Acid with N-Tosyl Oxaziridines
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A mild and efficient strategy for decarboxylative C(sp2)-C(sp3) and C(sp)-C(sp3) coupling of α,β-unsaturated carboxylic acids such as substituted cinnamic acids and 3-phenyl propiolic acid with N-Tosyl oxaziridines was developed. The corresponding products were achieved in moderate to good yields with excellent stereoselectivity. Base-free and oxidant-free conditions allow good functional group tolerance. Radical inhibitors such as TEMPO and BHT completely suppressed the reactions suggesting a radical mechanism was involved. This study is supposed to broaden the frontier of oxaziridines' chemistry and to open up a novel cascade for alkylating reagents.
- Nguyen, Bich-Ngoc,Cao, Hai-Thuong
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supporting information
p. 5912 - 5915
(2019/08/07)
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- A Highly Reduced Ni-Li-Olefin Complex for Catalytic Kumada-Corriu Cross-Couplings
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The catalytic activity of a highly reduced Ni catalyst in the context of a Kumada-Corriu cross-coupling has been studied. This nickel complex is characterized by its high electron density, stabilized by simple olefin ligands in combination with two Li ions. Landmark reactivity has been found with this precatalyst which operates at cryogenic temperatures, thus allowing the presence of sensitive functionalities. Structural elucidation of oxidative addition intermediates and their reactivity suggest highly reduced species being operative in the C-C bond forming event.
- Nattmann, Lukas,Lutz, Sigrid,Ortsack, Pascal,Goddard, Richard,Cornella, Josep
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supporting information
p. 13628 - 13633
(2018/10/24)
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- Copper- and Nickel-Catalyzed Cross-Coupling Reaction of Monofluoroalkenes with Tertiary, Secondary, and Primary Alkyl and Aryl Grignard Reagents
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A highly efficient cross-coupling reaction of monofluoroalkenes with tertiary, secondary, and primary alkyl and aryl Grignard reagents in the presence of a catalytic amount of copper or nickel catalyst, respectively, has been developed. The reactions proceeded smoothly at room temperature, providing (E)-alkene isomers in moderate to high yields. Plausible mechanisms of the Ni-catalyzed coupling reaction of monofluoroalkene with Grignard reagents are suggested.
- Shi, Hongyan,Dai, Wenpeng,Wang, Biyun,Cao, Song
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supporting information
p. 459 - 463
(2018/02/17)
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- Enantioselective Oxy-Heck–Matsuda Arylations: Expeditious Synthesis of Dihydrobenzofuran Systems and Total Synthesis of the Neolignan (?)-Conocarpan
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This work discloses the first examples of an effective enantioselective oxy-Heck–Matsuda reaction using a variety of styrenic olefins to generate chiral dihydrobenzofurans. The reaction proceeds in moderate to good yields, with high trans diastereoselectivity (up to 20:1) in enantioselectivities up to 90:10 using the N,N-ligand pyrimidine-bisoxazoline (PyriBox). The oxy-Heck–Matsuda reactions were carried out under mild conditions and rather low catalyst loadings. The feasibility and practicality of the process is demonstrated by a concise total synthesis of the neolignan (?)-conocarpan. X-ray diffraction of an advanced brominated intermediate in the route to (?)-conocarpan has allowed the unequivocal assignment of the absolute stereochemistry of the oxy-Heck–Matsuda aryldihydrobenzofuran products. A rationale for the mechanism operating in these enantioselective oxy-Heck–Matsuda reactions is also presented. (Figure presented.).
- Silva, Allan R.,Polo, Ellen C.,Martins, Nelson C.,Correia, Carlos Roque D.
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p. 346 - 365
(2018/01/26)
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- Radical Cation Cyclopropanations via Chromium Photooxidative Catalysis
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The chromium photocatalyzed cyclopropanation of diazo reagents with electron-rich alkenes is described. The transformation occurs under mild conditions and features specific distinctions from traditional diazo-based cyclopropanations (e.g., avoiding β-hydride elimination, chemoselectivity considerations, etc.). The reaction appears to work most effectively using chromium catalysis, and a number of decorated cyclopropanes can be accessed in generally good yields.
- Sarabia, Francisco J.,Ferreira, Eric M.
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supporting information
p. 2865 - 2868
(2017/06/07)
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- Orthogonally protected 1,2-diols from electron-rich alkenes using metal-free olefin syn-dihydroxylation
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A new method for the stereoselective metal-free syn-dihydroxylation of electron-rich olefins is reported, involving reaction with TEMPO/IBX in trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) and the addition of a suitable nucleophile. Orthogonally
- Colomer, Ignacio,Barcelos, Rosimeire Coura,Christensen, Kirsten E.,Donohoe, Timothy J.
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supporting information
p. 5880 - 5883
(2016/11/29)
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- Direct fluorination of styrenes
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We have developed a practical method to synthesize fluorostyrene compounds. A mild and regioselective mono-fluorination reaction occurred smoothly for various di- and trisubstituted styrenes in the presence of RuCl3 and N-fluorobenzenesulfonimide (NFSI). A tandem alkyne hydroarylation-olefin fluorination reaction was also developed using an Au catalyst.
- Shao, Qian,Huang, Yong
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supporting information
p. 6584 - 6586
(2015/04/14)
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- A transition-metal-free Heck-type reaction between alkenes and alkyl iodides enabled by light in water
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A transition-metal-free coupling protocol between various alkenes and non-activated alkyl iodides has been developed by using photoenergy in water for the first time. Under UV irradiation and basic aqueous conditions, various alkenes efficiently couple with a wide range of non-activated alkyl iodides. A tentative mechanism, which involves an atom transfer radical addition process, for the coupling is proposed.
- Liu, Wenbo,Li, Lu,Chen, Zhengwang,Li, Chao-Jun
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supporting information
p. 6170 - 6174
(2015/06/08)
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- Photocatalytic synthesis of dihydrobenzofurans by oxidative [3+2] cycloaddition of phenols
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We report a protocol for oxidative [3+2] cycloadditions of phenols and alkenes applicable to the modular synthesis of a large family of dihydrobenzofuran natural products. Visible-light-activated transition metal photocatalysis enables the use of ammonium persulfate as an easily handled benign terminal oxidant. The broad range of organic substrates that are readily oxidized by photoredox catalysis suggests that this strategy may be applicable to a variety of useful oxidative transformations.
- Blum, Travis R.,Zhu, Ye,Nordeen, Sarah A.,Yoon, Tehshik P.
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supporting information
p. 11056 - 11059
(2015/03/30)
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- Alkyl transfer from C-C cleavage: Replacing the nitro group of nitro-olefins
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Alkyl substituted Hantzsch esters are rationally used as alkylation reagents to replace the nitro groups of nitro olefins to give excellent yields of trans-olefins. The reaction mechanism is considered to proceed through a free radical mechanism, which is different from the corresponding transfer alkylation of imines. This journal is the Partner Organisations 2014.
- Li, Guangxun,Wu, Lei,Lv, Gang,Liu, Hongxin,Fu, Qingquan,Zhang, Xiaomei,Tang, Zhuo
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p. 6246 - 6248
(2014/06/09)
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- Directing group enhanced carbonylative ring expansions of amino-substituted cyclopropanes: Rhodium-catalyzed multicomponent synthesis of N-heterobicyclic enones
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Aminocyclopropanes equipped with suitable N-directing groups undergo efficient and regioselective Rh-catalyzed carbonylative C-C bond activation. Trapping of the resultant metallacycles with tethered alkynes provides an atom-economic entry to diverse N-heterobicyclic enones. These studies provide a blueprint for myriad N-heterocyclic methodologies.
- Shaw, Megan H.,Melikhova, Ekaterina Y.,Kloer, Daniel P.,Whittingham, William G.,Bower, John F.
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supporting information
p. 4992 - 4995
(2013/05/22)
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- Cu(I)-catalyzed, α-selective, allylic alkylation reactions between phosphorothioate esters and organomagnesium reagents
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Regiocontrol of allylic alkylation reactions involving hard nucleophiles remains a significant challenge and continues to be an active area of research. The lack of general methods in which α-alkylation is favored underscores the need for the development of new processes for achieving this type of selectivity. We report that Cu(I) catalyzes the allylic substitution of phosphorothioate esters with excellent α-regioselectivity, regardless of the nature of the Grignard reagent that is used. To the best of our knowledge, the Cu-catalyzed allylic alkylation of phosphorothioate esters has never been described. We have also developed a simple protocol for inducing high α selectivity starting from secondary allylic halides. This is accomplished by using sodium phosphorothioates as an additive.
- Lauer, Andrew M.,Mahmud, Farzeen,Wu, Jimmy
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supporting information; experimental part
p. 9119 - 9123
(2011/08/04)
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- One-pot synthesis of substituted styrenes from vicinal dibromoalkanes and arylboronic acids
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Dehydrobromination of vicinal dibromoalkanes in systems comprising 1,2-dimethoxy-ethane, N-butyl-N′-methylimidazolium tetrafluoroborate (or tetrabutylammonium bromide), and a base with subsequent palladium-catalyzed cross-coupling of the thus formed bromoalkenes with arylboronic acids furnished substituted styrenes. Springer Science+Business Media, Inc. 2007.
- Tikhonov,Vasil'ev,Chirskaya,Struchkova,Merkulova,Zlotin
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p. 122 - 129
(2008/02/08)
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- A simple radical addition - Elimination route to geometrically pure (E)-alkene and chromanone derivatives via β-nitrostyrene
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Various geometrically pure (E)-β-alkyl-styrenes have been synthesized by the radical NO2 substitution of alkyl moieties generated via hydrogen abstraction followed by decarbonylation from aliphatic aldehydes. These reactions, which involve a high chemical selectivity and regioselectivity constitute a new route to (E)-β-alkylstyrenes. Both aliphatic and aromatic aldehydes can be used in this novel reaction. When 2-allyloxybenzaldehyde was used, the benzoyl radical added directly to the double bond without decarbonylation to give the 3-cinnamylchroman-4-one. This unique difference between aliphatic and aromatic aldehydes represents a simple route for the synthesis of biologically important chromanones.
- Jang, Yeong-Jiunn,Yan, Ming-Chung,Lin, Yung-Feng,Yao, Ching-Fa
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p. 3961 - 3963
(2007/10/03)
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- Novel synthesis of alkenes via triethylborane-induced free-radical reactions of alkyl iodides and β-nitrostyrenes
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Reactions of (E)-β-nitrostyrenes 1 and triethylborane 2 or tricyclohexylborane 4 in THF solution at room temperature in the presence of oxygen in the air as radical initiator generate high yields of trans-alkenes (E)-3 or (E)-5. Medium to high yields of d
- Liu,Jang,Shih,Hu,Chu,Yao
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p. 6021 - 6028
(2007/10/03)
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- Novel synthesis of alkenes via triethylaluminum-induced free radical reactions of alkyl iodides and β-nitrostyrenes
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Reactions of (E)-β-nitrostyrenes 1 with triethylaluminum (Et3Al) 2 and alkyl iodide (RI) 3, 4, or 5 in the presence of benzoyl peroxide in diethyl ether solution at room temperature to give 60-100% of the different (E)-alkenes 6, 7, or 8. Under
- Liu, Jing-Yuan,Liu, Ju-Tsung,Yao, Ching-Fa
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p. 3613 - 3615
(2007/10/03)
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- One-pot synthesis of trans-β-alkylstyrenes
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One-pot synthesis of (E)-alkenes 5 from the reactions of aldehyde 1 and nitromethane 2 in the acetic acid solution and then with triethylborane 4 in the biphase of diethyl ether and aqueous solution in the presence of oxygen in air was reported. Various (E)-alkenes 7 could also be prepared when different kinds of secondary or tertiary alkyl iodides 6 were used under similar conditions.
- Liu, Ju-Tsung,Yao, Ching-Fa
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p. 6147 - 6150
(2007/10/03)
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- The stereoselective Horner-Wittig reaction with phoshine oxides: Synthesis of hindered Z alkenes via Luche reduction
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The natural anti selectivity of the Horner-Wittig reaction with phospine oxides is reduced when there is a branched chain next to the new C=C double bond. A better approach is Luche reduction of the corresponding ketones which gives high anti selectivity when the branched chain is placed on the side chain next to the phosphine oxide.
- Hutton,Jolliff,Mitchell,Warren
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p. 7905 - 7908
(2007/10/02)
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- Arylcyclopropane Photochemistry. Substituent Effects on the Photochemical 1,3-Hydrogen Migration of 1,1-Dimethyl-2-phenylcyclopropane
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Irradiation of 1,1-dimethyl-2-arylcyclopropanes 1a-g (Ar = p-CF3C6H4 (1a), m-CF3C6H4 (1b), p-CH3C6H4 (1c), m-CH3C6H4 (1d), C6H5 (1e), m-OCH3C6H4 (1f), p-OCH3C6H4 (1g) gave in every case a 2-methyl-4-aryl-1-butene (2a-g) via a 1,3-hydrogen migration, accompanied by lesser amounts of a 3-methyl-1-aryl-2-butene (3a-g).Rearrangement is a singlet-state process.Rate constants for rearrangement were determined from reactant fluorescence lifetimes and product quantum yields.The rates for rearrangament of 1 to 2 were as follows:1a, 25*106s-1; 1b,15*106s-1; 1c, 7.9*106s-1; 1d, 6.1*106s-1; 1e, 2.3*106s-1; 1f, 1.9*106s-1; 1g, 0.87*106s-1.It isconcluded that the energetics of cyclopropane ring opening are important in the rate-determining step of the reaction.
- Hixson, Stephen S.,Gallucci, Charles R.
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p. 2711 - 2713
(2007/10/02)
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- The Stereocontrolled Horner-Wittig Reaction: Synthesis of Disubstituted Alkenes
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Addition of the lithium derivatives of phosphine oxides Ph2P(O)CH2R1 to aldehydes gives erythro adducts (11) with good stereoselectivity.Reduction of α-diphenylphosphinoyl ketones (12) gives threo adducts (11) with even better stereoselectivity.Purification by flash chromatography and/or crystallisation followed by elimination of Ph2PO2 gives pure Z- or E-alkenes with high material conversion.Explanations are offered for the stereoselectivities, conditions defined for full stereochemical control, and guidelines suggested for approaches to a given alkene.
- Buss, Antony D.,Warren, Stuart
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p. 2307 - 2326
(2007/10/02)
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- Reactivity of Aryl Vinyl Di-?-methane Systems. Mechanistic and Exploratory Organic Photochemistry
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The di-?-methane rearrangement of a series of meta and para substituted arylvinylmethane reactants was investigated with the aim of determiningthe patterns of reactivity in systems in which initial excitation is localized in the aryl moiety.Thus the photo
- Zimmerman, Howard E.,Swafford, Richard L.
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p. 3069 - 3083
(2007/10/02)
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