- Dual-Role Catalysis by Thiobenzoic Acid in Cα-H Arylation under Photoirradiation
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Thiobenzoic acid (TBA) can serve as a single-electron reducing agent under photoirradiation from a blue light-emitting diode, in the presence of appropriate electron acceptors, and the resulting sulfur-centered radical species undergoes hydrogen atom abstraction. This dual-role catalysis by TBA enables regioselectivie Cα-H arylation of benzylamines, benzyl alcohols, and ethers, as well as dihydroimidazoles, with cyano(hetero)arenes in good yield, without the need for a transition-metal photocatalyst and/or synthetically elaborated organic dyes.
- Kobayashi, Fumihisa,Fujita, Masashi,Ide, Takafumi,Ito, Yuta,Yamashita, Kenji,Egami, Hiromichi,Hamashima, Yoshitaka
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- Oxidative and Redox-Neutral Approaches to Symmetrical Diamines and Diols by Single Electron Transfer/Hydrogen Atom Transfer Synergistic Catalysis
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Homocoupling reactions of benzylamines and benzyl alcohols were examined under synergistic catalysis conditions with a photoredox catalyst and thiobenzoic acid as a hydrogen atom abstractor. When pivalaldehyde was used as an electron acceptor, oxidative dimerization proceeded selectively, whereas the use of benzaldehydes or iminium ions as electron acceptors resulted in redox-neutral coupling. These reactions afforded symmetrical 1,2-diamines and 1,2-diols in good yields.
- Fujita, Masashi,Kobayashi, Fumihisa,Ide, Takafumi,Egami, Hiromichi,Hamashima, Yoshitaka
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supporting information
p. 7151 - 7155
(2020/12/01)
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- Visible light mediated homo- and heterocoupling of benzyl alcohols and benzyl amines on polycrystalline cadmium sulfide
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The oxidative coupling of sp3 hybridized carbon atoms by photocatalysis is a valuable synthetic method as stoichiometric oxidation reagents can be avoided and dihydrogen is the only byproduct of the reaction. Cadmium sulfide, a readily available semiconductor, was used as a visible light heterogeneous photocatalyst for the oxidative coupling of benzyl alcohols and benzyl amines by irradiation with blue light. Depending on the structure of the starting material, good to excellent yields of homocoupling products were obtained as mixtures of diastereomers. Cross-coupling between benzyl alcohols and benzyl amines gave product mixtures, but was selective for the coupling of tetrahydroisoquinolines to nitromethane. The results demonstrate that CdS is a suitable visible light photocatalyst for oxidative bond formation under anaerobic conditions.
- Mitkina, Tatiana,Stanglmair, Christoph,Setzer, Wolfgang,Gruber, Michael,Kisch, Horst,Koenig, Burkhard
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supporting information; experimental part
p. 3556 - 3561
(2012/06/01)
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- Reductive coupling of aromatic N,N-acetals using zinc and chlorotrimethylsilane
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The reductive coupling of aromatic N,N-acetals and N,O-acetal activated by chlorotrimethylsilane proceeded smoothly in the presence of zinc to give the corresponding diamines in good yields.
- Hatano, Bunpei,Tachikawa, Tomoharu,Mori, Tetsunori,Nagahashi, Keita,Kijima, Tatsuro
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supporting information; experimental part
p. 3467 - 3469
(2011/07/08)
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- Titanocene-catalyzed coupling of aromatic amides in the presence of organosilanes: A novel route to vicinal diamines and a new class of amine-substituted oligomers
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The title reaction has been surveyed for a number of substrates with differing substitution patterns. With a few exceptions, the methodology provides a one-pot synthesis of the 1,2-diamines from widely available and inexpensive starting materials, and in high yields. In addition, the coupling of 1,4-and 1,3-bis-(N,N,N′,N′-tetraalkyl)arylenediamides is shown, under the same experimental conditions, to yield oligomers: R2NC(O)C 6H4CH(NR2)-[CH(NR2)C 6H4CH(NR2)]n-CH(NR 2)C6H4C(O)-NR2 (R = methyl and ethyl; n = 0 to ca. 5). The chemical structures of these unprecedented oligomers are determined by comparison of NMR and MS spectra to those of vicinal diamines, prepared from the analogous N,N-dialkylbenzamides. The origin of the limitation of oligomer chain length is probably due to a specific effect of the internal benzylic amine group, since the substrate 4-Me2NCH 2C6H4C(O)NMe2 was found to be uniquely unreactive compared to the other 4-substituted N,N-dialkylbenzamides investigated. N-Methylphthalimide was briefly studied as a monomer and analysis by MS showed that oligomers are formed. Attempts to fully characterize these polymers were unsuccessful.
- Rangareddy, Kesamreddy,Selvakumar, Kumaravel,Harrod, John F.
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p. 6843 - 6850
(2007/10/03)
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- Iminopinacol coupling with lithium: Electron-transfer mediators
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The addition of tert-butyl borate or ethyl formate to N-alkylbenzalimines directs the reaction pathway from the Birch reduction to the pinacol-type coupling with lithium in THF; an analogous reaction with a dimethylimmonium salt requires a trace titanium catalyst as the electron-transfer mediator.
- Mistryukov, Electron A.
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p. 230 - 231
(2007/10/03)
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- 211. Scope and Limitations of the Reductive Coupling of Aromatic Aldimine Derivatives with Formation of 1,2-Diarylethylenediamine Units, Using Low-Valent Titanium Reagents
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Besides the adducts from lithium amides to aromatic aldehydes, iminium salts, aminals, and N-silylimines of aromatic aldehydes are coupled by the black suspension obtained from TiCl4 and Mg turnings in tetrahydrofuran (THF).The 1,2-diarylethylenediamines with tertiary and primary amino groups thus obtained are formed with no or only moderate diastereoselectivity (products 4a-d (Scheme 2) and 5a-e (Scheme 3), respectively); the amine component may contain a strained ring or additional heteroatoms as in azetidin, bis(2-metoxyethyl)amine piperazine, morpholine, and thiomorpholine (products 6a-e; Table 1).By an in-situ procedure, ethylenediamines and propane-1,3-diamines with two secondary amino groups are cyclized with aromatic aldehydes to give exclusively trans-diaryl-substituted piperazine and perhydro-1,4-diazepine derivatives (products 7a-f; Table 2).Enantiomerically pure monocyclic trans,cis-5-alkyl-2,3-diaryl-piperazines and diazabicyclononanes and -decanes are obtained by employing suitable diamines prepared from the amino acids (S)-alanine, (S)-phenylalanine, (S)-proline, and from (S,S)- or (R,R)-cyclohexane-1,2-diamine, respectively (products 11a-i, 7e; Table 4).The configurations of all products are derived from the high-field NMR spectra, some of which are discussed in detail (Figs. 1 and 2, Tables 3 and 5); all new compounds are fully characterized by their physical data.Depending upon the structure of the components employed, the yields of purified products range from as low as 7percent to essentially quantitative.
- Betschart, Claudia,Schmidt, Beat,Seebach, Dieter
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p. 1999 - 2021
(2007/10/02)
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- Use of Carboxylic Acids as Chiral Solvating Agents for the Determination of Optical Purity of Chiral Amines by NMR Spectroscopy
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Optically pure mandelic acid, Mosher's acid, and N-(3,5-dinitrobenzoyl)phenylglycine have been used as chiral solvating agents to induce nonequivalence in the 1H NMR spectra of several diamines, amino acid esters, amino alcohols, and other amines.The identity of the chiral solvating agent and the stoichiometry of the solvation complexes that yield the greatest nonequivalence varies with the nature of the substrate.
- Benson, Scott C.,Cai, Ping,Colon, Marcelo,Haiza, Mohammed A.,Tokles, Maritherese,Snyder, John K.
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p. 5335 - 5341
(2007/10/02)
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- 208. Aminierende reduktive Kupplung aromatischer Aldehyde mit niedervalenten Titan-Reagenzien zu 1,2-Diarylethylendiaminen
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In a novel McMurry-type one-pot reaction, aromatic aldehydes and secondary amines are coupled to give the N,N,N',N'-tetralkyl-1,2-diarylethylendiamines 1-22 (Table 3).To this end, a lithium dialkylamide is added to an aromatic aldehyde to give the adduct B which is then treated with 1 equiv. of TiCl4 to yield a coloured suspension of a reagent synthetically equivalent to a iminium salt (C/D in Scheme 4).After treatment with a low-valent Ti reagent which is prepared by reduction of TiCl4 with either K or, preferably, Mg, the coupling products are isolated in 23 to 81 percent yield as a 1:1 mixture of the diastereoisomers (meso- and rac-form).These are separated either by chromatography or by crystallization and characterized.
- Betschart, Claudia,Seebach, Dieter
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p. 2215 - 2231
(2007/10/02)
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- Aminierende, reduktive Kupplung aromatischer Aldehyde mit Tris(dialkylamino)methylvanadium(IV) zu N,N,N',N'-Tetraalkyl-1,2-diarylaethylendiaminen
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In a novel type of reaction, certain aromatic aldehydes (benzaldehyde, p-methoxy-benzaldehyde, 1-naphthaldehyde, furan-2-carbaldehyde) and secondary amines are coupled to give N,N,N',N'-tetraalkyl-1,2-diarylethylenediamines 1-6.The reagents are tris(dialkylamino)methylvanadium(IV) compounds (cf.Eqn.2).These are generated in situ either from isolable chlorotris(dialkylamino)vanadium(IV) (Eqn. 3), or preferably, from an Et2O/pentane solution of VCl4 which is treated sequentially with 3 equiv. of lithium dialkylamide, 1 equiv. of MeLi, and equiv. of aromatic aldehyde, to give the products 1-6 in a one-pot preparation (Schem 2).The yields range from 14 to 54percent.The diastereomeric mixtures (meso- and (+/-)forms) obtained are separated by chromatography (Al2O3, petroleum ether/Et2O/Et3N), and the pure stereoisomers fully characterized.A mechanism of the reductive coupling induced by CH3V(NR2)3 is proposed (Scheme 1).
- Imwinkelried, Rene,Seebach, Dieter
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p. 1496 - 1502
(2007/10/02)
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- Studies on the Occurrence of Hydrogen Transfer, 73. - The Reduction of Prochiral Alkyl (Aryl) Ketones with Alkali Metal Amalgams Forming Carbinols and Pinakols
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The factors are determined which influence the stereochemistry and the ratio (C/P) in the reduction of acetophenone with lithium, sodium, and potassium amalgam (Li/Hg, Na/Hg, K/Hg) leading to carbinol (C) and pinacol(P).The C/P ratio is influenced a) by proton donators, b) by quaternaryammonium salts, c) by bis-tertiary amines.In the presence of optically active quaternary ammonium salts and optically active bis-tertiary amines a low optical induction is observed both in pinacol and carbinol.An anomal dimerization product 20 is formed in the reduction of pivalophenone with Li/Hg.
- Horner, Leopold,Dickerhof, Karlheinz
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p. 1240 - 1258
(2007/10/02)
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- PHOSPHORORGANISCHE VERBINDUNGEN 102. TERTIAERE PHOSPHINE MIT o-DIALKYLAMINOPHENYL- UND ORTHO-DIALKYLAMINOBENZYLGRUPPEN
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N,N-dialkylarylamines and N,N-dialkylbenzylamines are lithiated with n-butyllithium (n-BuLi) under the assistance of tetramethylethylenediamine (TMEDA) in the ortho-position.According the Eqs. (1) and (4) triarylphosphines (30-50percent) are obtained. 1-(N,N-dimethylamino)-naphthalene and N,N-dimethyl-1-(1-naphthyl)-ethylamine 18 are lithiated in the 8-position.In N,N-dimethyl-1-(2-naphthyl)-ethylamine 19 the 1- and 3-position is lithiated in nearly equal amount.Experiments to introduce lithium twice into the model compounds 28-30 are without success.
- Horner, L.,Simons, G.
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p. 165 - 176
(2007/10/02)
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