- Reductive activation and hydrofunctionalization of olefins by multiphoton tandem photoredox catalysis
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The conversion of olefin feedstocks to architecturally complex alkanes represents an important strategy in the expedient generation of valuable molecules for the chemical and life sciences. Synthetic approaches are reliant on the electrophilic activation of unactivated olefins, necessitating functionalization with nucleophiles. However, the reductive functionalization of unactivated and less activated olefins with electrophiles remains an ongoing challenge in synthetic chemistry. Here, we report the nucleophilic activation of inert styrenes through a photoinduced direct single electron reduction to the corresponding nucleophilic radical anion. Central to this approach is the multiphoton tandem photoredox cycle of the iridium photocatalyst [Ir(ppy)2(dtbbpy)] PF6, which triggers in situ formation of a high-energy photoreductant that selectively reduces styrene olefinic π bonds to radical anions without stoichiometric reductants or dissolving metals. This mild strategy enables the chemoselective reduction and hydrofunctionalization of styrenes to furnish valuable alkane and tertiary alcohol derivatives. Mechanistic studies support the formation of a styrene olefinic radical anion intermediate and a Birch-type reduction involving two sequential single electron transfers. Overall, this complementary mode of olefin activation achieves the hydrofunctionalization of less activated alkenes with electrophiles, adding value to abundant olefins as valuable building blocks in modern synthetic protocols.
- Czyz, Milena L.,Taylor, Mitchell S.,Horngren, Tyra H.,Polyzos, Anastasios
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p. 5472 - 5480
(2021/06/01)
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- Bioinspired Metal-Free Formal Decarbonylation of α-Branched Aliphatic Aldehydes at Ambient Temperature
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A sequence of a Baeyer–Villiger oxidation and a Lewis acid-promoted reduction of the resulting formate with Et3SiH enabled the metal-free formal decarbonylation of tertiary and secondary aliphatic aldehydes. The new methodology mimics the biosynthetic decarbonylation pathway through oxidative C?C bond cleavage rather than the C(O)?H bond activation known from conventional Tsuji–Wilkinson-type reactions. The substrate scope is complementary to existing transition-metal-catalyzed protocols.
- Richter, Sven C.,Oestreich, Martin
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supporting information
p. 8508 - 8512
(2019/06/04)
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- Nickel-catalyzed cross-coupling of umpolung carbonyls and alkyl halides
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An effective nickel-catalyzed cross-coupling of Umpolung carbonyls and alkyl halides was developed. Complementary to classical alkylation techniques, this reaction utilizes Umpolung carbonyls as the environmentally benign alkyl nucleophiles, providing an efficient and selective catalytic alternative to the traditional use of highly reactive alkyl organometallic reagents.
- Zhu, Dianhu,Lv, Leiyang,Qiu, Zihang,Li, Chao-Jun
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- Nickel-Catalyzed Cross-Coupling of Umpolung Carbonyls and Alkyl Halides
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An effective nickel-catalyzed cross-coupling of Umpolung carbonyls and alkyl halides was developed. Complementary to classical alkylation techniques, this reaction utilizes Umpolung carbonyls as the environmentally benign alkyl nucleophiles, providing an efficient and selective catalytic alternative to the traditional use of highly reactive alkyl organometallic reagents.
- Zhu, Dianhu,Lv, Leiyang,Qiu, Zihang,Li, Chao-Jun
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p. 6312 - 6322
(2019/05/24)
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- Cyclohexa-1,3-diene-based dihydrogen and hydrosilane surrogates in B(C6F5)3-catalysed transfer processes
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The cyclohexa-1,3-diene motif is introduced as an equally effective alternative to the cyclohexa-1,4-diene platform in B(C6F5)3-catalysed transfer processes. The transfer hydrogenation of alkenes is realised with α-terpinene and the related transfer hydrosilylation is achieved with 5-trimethylsilyl-substituted cyclohexa-1,3-diene. Both yields and substrate scope are comparable with the prior systems.
- Yuan, Weiming,Orecchia, Patrizio,Oestreich, Martin
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supporting information
p. 10390 - 10393
(2017/09/25)
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- Br?nsted Acid-Catalyzed Transfer Hydrogenation of Imines and Alkenes Using Cyclohexa-1,4-dienes as Dihydrogen Surrogates
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Cyclohexa-1,4-dienes are introduced to Br?nsted acid-catalyzed transfer hydrogenation as an alternative to the widely used Hantzsch dihydropyridines. While these hydrocarbon-based dihydrogen surrogates do offer little advantage over established protocols in imine reduction as well as reductive amination, their use enables the previously unprecedented transfer hydrogenation of structurally and electronically unbiased 1,1-di- and trisubstituted alkenes. The mild procedure requires 5.0 mol % of Tf2NH, but the less acidic sulfonic acids TfOH and TsOH work equally well.
- Chatterjee, Indranil,Oestreich, Martin
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supporting information
p. 2463 - 2466
(2016/06/09)
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- B(C6F5)3-Catalyzed Transfer of Dihydrogen from One Unsaturated Hydrocarbon to Another
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A transition-metal-free transfer hydrogenation of 1,1-disubstituted alkenes with cyclohexa-1,4-dienes as the formal source of dihydrogen is reported. The process is initiated by B(C6F5)3-mediated hydride abstraction from the dihydrogen surrogate, forming a Bronsted acidic Wheland complex and [HB(C6F5)3]-. A sequence of proton and hydride transfers onto the alkene substrate then yields the alkane. Although several carbenium ion intermediates are involved, competing reaction channels, such as dihydrogen release and cationic dimerization of reactants, are largely suppressed by the use of a cyclohexa-1,4-diene with methyl groups at the C1 and C5 as well as at the C3 position, the site of hydride abstraction. The alkene concentration is another crucial factor. The various reaction pathways were computationally analyzed, leading to a mechanistic picture that is in full agreement with the experimental observations.
- Chatterjee, Indranil,Qu, Zheng-Wang,Grimme, Stefan,Oestreich, Martin
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supporting information
p. 12158 - 12162
(2015/10/12)
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- Enantiopure C1-symmetric bis(imino)pyridine cobalt complexes for asymmetric alkene hydrogenation
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Enantiopure C1-symmetric bis(imino)pyridine cobalt chloride, methyl, hydride, and cyclometalated complexes have been synthesized and characterized. These complexes are active as catalysts for the enantioselective hydrogenation of geminal-disubstituted olefins.
- Monfette, Sebastien,Turner, Zoe R.,Semproni, Scott P.,Chirik, Paul J.
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p. 4561 - 4564
(2012/04/23)
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- Zr-catalyzed coupling reaction of alkyl halides, tosylates, and sulfates with β-phenethyl Grignard reagents via styrene-zirconate intermediates
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β-Phenethylmagnesium chlorides react with alkyl halides, tosylates, and sulfates in the presence of a catalytic amount of Cp2ZrCl 2 to afford 2-arylalkanes via alkylation of styrene-zirconate intermediates at the benzylic position. Competitive reaction using mixtures of alkyl halides (alkyl-X; X = F, Cl, Br) showed that the reactivities of the halides increase in the order of alkyl-Cl alkyl-F alkyl-Br with the relative rates of 1:19:428. Georg Thieme Verlag Stuttgart.
- Terao, Jun,Begum, Shameem Ara,Oda, Akihiro,Kambe, Nobuaki
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p. 1783 - 1786
(2007/10/03)
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- Zirconocene-catalyzed alkylation of aryl alkenes with alkyl tosylates, sulfates and bromides
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Styrenes were alkylated with alkyl tosylates, sulfates and bromides in the presence of a zirconocene catalyst and (n)BuMgCl in THF. By the use of this reaction, primary and secondary alkyl groups can be introduced regioselectively at the benzylic carbon of styrenes to give α-substituted ethylbenzenes.
- Terao, Jun,Watanabe, Tsunenori,Saito, Koyu,Kambe, Nobuaki,Sonoda, Noboru
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p. 9201 - 9204
(2007/10/03)
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- Synthesis of (R)-2-diphenylphosphino-2′-diphenylphosphinomethyl-1,1′-binaphthyl and its use for asymmetric hydrogenation of α-alkylstyrenes
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A new chiral bisphosphine ligand ((R)-2-diphenylphosphino-2′-diphenylphosphinomethyl-1,1′-binaphthyl) was synthesized from enantiomerically pure (R)-1,1′-binaphthalene-2,2′-diol. Rhodium(I) complexes of this bisphosphine ligand have been used as catalysts for asymmetric hydrogenation of α-alkylstyrenes to give the corresponding aromatic hydrocarbons in up to 77% ee.
- Inagaki, Kohji,Ohta, Tetsuo,Nozaki, Kyoko,Takaya, Hidemasa
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p. 159 - 163
(2007/10/03)
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- On the Twofold Heck Reaction of 4-Vinylcyclohexene and p-Dihalobenzenes
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The palladium-catalyzed reaction of iodobenzene, p-haloiodobenzenes (p-C6H4IX'; X' = F, Cl, Br, I) and p-dibromobenzene with 4-vinylcyclohexene (Heck arylation reaction of olefins) was investigated with Pd(OAc)2/PR3/Et3N (R = phenyl, o-tolyl) as a classic
- Lorenz, Peter,Becher, Diana,Steinborn, Dirk,Poetsch, Eike,Akermark, Bjoern
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p. 375 - 378
(2007/10/02)
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- Photodecarboxylation of 2-phenylpropionic acid in solution and included within β-cyclodextrin
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Photolysis of 2-phenylpropionic acid (1) in acetonitrile, methanol or benzene leads to ethylbenzene (2), 2,3-diphenylbutane (3d,l and meso), 1-(2-ethylphenyl)-1-phenylethane (4), 1-(4-ethylphenyl)-1-phenylethane (5) and acetophenone (6). In cyclohexane or carbon tetrachloride, solvent derived products are formed. These results involve homolytic cleavage of the C-C bond α to the carboxy group, which affords 1-phenylethyl radical (PER) as key intermediate. The α,α coupling of PER in solution to give 3 is nonstereoselective; by contrast, formation of the meso isomer is preferred upon inclusion of 1 within β-cyclodextrin. This is attributed to the coupling of two long-lived PER-CD units.
- Consuelo Jimenez,Miranda, Miguel A.,Tormos, Rosa
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p. 2953 - 2958
(2007/10/02)
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- Synthesis and Ring Cleavage of Highly Substituted 1,1-Dichloro- and 1-Bromo-1-fluorocyclopropanes
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The tri- and tetrasubstituted olefines 1, 2, 4, 7 - 15, and 19 react with CCl2 to give the dichlorocyclopropanes 22, 23, 25, 26a - 30a, and 33a - 37a in high yield, while the highly sterically hindered olefins 5, 6, and 21 show no reaction.In a few border
- Anke, Lutz,Reinhard, Detlef,Weyerstahl, Peter
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p. 591 - 602
(2007/10/02)
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