22927-07-7Relevant articles and documents
Reactions of benzyltriphenylphosphonium salts under photoredox catalysis
Boldt, Andrew M.,Dickinson, Sidney I.,Ramirez, Jonathan R.,Benz-Weeden, Anna M.,Wilson, David S.,Stevenson, Susan M.
supporting information, p. 7810 - 7815 (2021/09/28)
The development of benzyltriphenylphosphonium salts as alkyl radical precursors using photoredox catalysis is described. Depending on substituents, the benzylic radicals may couple to form C-C bonds or abstract a hydrogen atom to form C-H bonds. A natural product, brittonin A, was also synthesized using this method.
Tunable and Practical Homogeneous Organic Reductants for Cross-Electrophile Coupling
Barth, Emily L.,Charboneau, David J.,Germe, Cameron C.,Hazari, Nilay,Huang, Haotian,Mercado, Brandon Q.,Uehling, Mycah R.,Zultanski, Susan L.
supporting information, p. 21024 - 21036 (2021/12/14)
The syntheses of four new tunable homogeneous organic reductants based on a tetraaminoethylene scaffold are reported. The new reductants have enhanced air stability compared to current homogeneous reductants for metal-mediated reductive transformations, such as cross-electrophile coupling (XEC), and are solids at room temperature. In particular, the weakest reductant is indefinitely stable in air and has a reduction potential of -0.85 V versus ferrocene, which is significantly milder than conventional reductants used in XEC. All of the new reductants can facilitate C(sp2)-C(sp3) Ni-catalyzed XEC reactions and are compatible with complex substrates that are relevant to medicinal chemistry. The reductants span a range of nearly 0.5 V in reduction potential, which allows for control over the rate of electron transfer events in XEC. Specifically, we report a new strategy for controlled alkyl radical generation in Ni-catalyzed C(sp2)-C(sp3) XEC. The key to our approach is to tune the rate of alkyl radical generation from Katritzky salts, which liberate alkyl radicals upon single electron reduction, by varying the redox potentials of the reductant and Katritzky salt utilized in catalysis. Using our method, we perform XEC reactions between benzylic Katritzky salts and aryl halides. The method tolerates a variety of functional groups, some of which are particularly challenging for most XEC transformations. Overall, we expect that our new reductants will both replace conventional homogeneous reductants in current reductive transformations due to their stability and relatively facile synthesis and lead to the development of novel synthetic methods due to their tunability.
The synergy between the CsPbBr3nanoparticle surface and the organic ligand becomes manifest in a demanding carbon-carbon coupling reaction
Casadevall, Carla,Claros, Miguel,Galian, Raquel E.,Lloret-Fillol, Julio,Pérez-Prieto, Julia,Rosa-Pardo, Ignacio,Schmidt, Luciana
supporting information, p. 5026 - 5029 (2020/05/18)
We demonstrate here the suitability of CsPbBr3nanoparticles as photosensitizers for a demanding photoredox catalytic homo- and cross-coupling of alkyl bromides at room temperature by merely using visible light and an electron donor, thanks to the cooperative action between the nanoparticle surface and organic capping.
Simpler and Cleaner Synthesis of Variously Capped Cobalt Nanocrystals Applied in the Semihydrogenation of Alkynes
Moisset, A.,Petit, C.,Petit, M.,Salzemann, C.,Sodreau, A.,Vivien, A.
supporting information, p. 13972 - 13978 (2020/10/09)
Unlike the classical organometallic approach, we report here a synthetic pathway requiring no reducing sources or heating to produce homogeneous hexagonal-close-packed cobalt nanocrystals (Co NCs). Involving a disproportionation process, this simple and fast (6 min) synthesis is performed at room temperature in the presence of ecofriendly fatty alcohols to passivate Co NCs. Through a recycling step, the yield of Co NCs is improved and the waste generation is limited, making this synthetic route cleaner. After an easy exchange of the capping ligands, we applied them as unsupported catalysts in the stereoselective semihydrogenation of alkynes.
Ni-Catalyzed Iterative Alkyl Transfer from Nitrogen Enabled by the in Situ Methylation of Tertiary Amines
Nwachukwu, Chideraa Iheanyi,McFadden, Timothy Patrick,Roberts, Andrew George
, p. 9979 - 9992 (2020/09/03)
Current methods to achieve transition-metal-catalyzed alkyl carbon-nitrogen (C-N) bond cleavage require the preformation of ammonium, pyridinium, or sulfonamide derivatives from the corresponding alkyl amines. These activated substrates permit C-N bond cleavage, and their resultant intermediates can be intercepted to affect carbon-carbon bond-forming transforms. Here, we report the combination of in situ amine methylation and Ni-catalyzed benzalkyl C-N bond cleavage under reductive conditions. This method permits iterative alkyl group transfer from tertiary amines and demonstrates a deaminative strategy for the construction of Csp3-Csp3 bonds. We demonstrate PO(OMe)3 (trimethylphosphate) to be a Ni-compatible methylation reagent for the in situ conversion of trialkyl amines into tetraalkylammonium salts. Single, double, and triple benzalkyl group transfers can all be achieved from the appropriately substituted tertiary amines. Transformations developed herein proceed via recurring events: The in situ methylation of tertiary amines by PO(OMe)3, Ni-catalyzed C-N bond cleavage, and concurrent Csp3-Csp3 bond formation.
Novel preparation of N-arylmethyl-N-arylmethyleneamine N-oxides from benzylic bromides with zinc and isobutyl nitrite
Yanai, Kei,Togo, Hideo
, p. 3523 - 3529 (2019/05/24)
Treatment of benzylic bromides with Zn and LiCl, followed by the reaction with i-butyl nitrite gave N-arylmethyl-N-arylmethyleneamine N-oxides in moderate yields. The present reaction is a novel and simple method for the preparation of nitrones from benzylic bromides, although the yields are moderate.
Mechanistic Insights into Concerted C-C Reductive Elimination from Homoleptic Uranium Alkyls
Johnson, Sara A.,Higgins, Robert F.,Abu-Omar, Mahdi M.,Shores, Matthew P.,Bart, Suzanne C.
supporting information, p. 3491 - 3497 (2017/10/03)
A mechanistic study was carried out to probe concerted C-C reductive elimination from homoleptic uranium(IV) alkyls. The para-chloro uranium(IV) tetrabenzyl derivative, U(CH2-p-ClC6H4)4 (2-p-Cl), was synthesized by treating UCl4 with 4 equivalents of KCH2-p-Cl-Ph (1-p-Cl) at 108 °C, adding a new member to the previously reported family of uranium alkyl complexes U(CH2C6H5)4 (2-Bn), U(CH2-p-iPrC6H4)4 (2-p-iPr), U(CH2-ptBu-C6H4)4 (2-p-tBu), U(CH2-o-OMeC6H4)4 (2-o-OMe), and U(CH2-m-OMeC6H4)4 (2-m-OMe). Each member of this family readily reacts with the redox-active α-diimine ligand, MesDABMe (MesDABMe = [MesN = C(Me)C(Me) = NMes]; Mes = 2,4,6-trimethylphenyl), to afford the products from C-C reductive elimination, namely, (MesDABMe)U(CH2Ph′)2 and Ph′CH2CH2Ph′ (Ph′ = p-iPrC6H4, p-tBuC6H4, m-OMeC6H4, p-ClC6H4). Room-temperature magnetic-susceptibility values, obtained via SQUID magnetometry, show a correlation with an increase in the magnetic moment as the electron-withdrawing character of the substituent increases. Kinetic studies were used to assess the effect of the benzyl substituent on the rate of reductive elimination, showing that reaction rate increases as the electron-withdrawing nature of the substitution increases. Eyring data revealed a large and negative entropy value, indicative of a highly ordered transition state, consistent with the previously reported concerted elimination concluded from crossover experiments.
Mechanism and Applications of the Photoredox Catalytic Coupling of Benzyl Bromides
Park, Gyurim,Yi, Seung Yeon,Jung, Jaehun,Cho, Eun Jin,You, Youngmin
, p. 17790 - 17799 (2016/11/28)
The photoredox catalytic coupling of halomethyl arenes to bibenzyl derivatives has been demonstrated. The catalytic protocol employed the Hantzsch ester, potassium phosphate, and a photoactive cyclometalated IrIIIcomplex catalyst. A photochemical quantum yield as high as 20 % was obtained. The catalytic mechanism was investigated in detail by performing photophysical and electrochemical measurements, as well as by quantum chemical calculations. The results suggest that two-electron mediation might be responsible for the improved photon economy. The reaction protocol was compatible with halomethyl arenes that contain a variety of functional groups. Finally, the synthetic utility of our protocol was demonstrated by the preparation of a natural dihydrostilbenoid, brittonin A.
Cyclopentadienyl nickel(ii) N, C-chelating benzothiazolyl NHC complexes: Synthesis, characterization and application in catalytic C-C bond formation reactions
Teo, Wei Jie,Wang, Zhe,Xue, Fei,Andy Hor,Zhao, Jin
, p. 7312 - 7319 (2016/06/01)
Cyclopentadienyl (Cp) Ni(ii) complexes [CpNiL][PF6] containing hybrid N,C chelating benzothiazolyl NHC ligands (L1 = 1-(2-benzothiazolyl)-3-methylimidazol-2-ylidene, 3a; L2 = 1-(2-benzothiazolyl)-3-allylimidazol-2-ylidene, 3b; L3 = 1-(2-benzothiazolyl)-3-benzylimidazol-2-ylidene, 3c) have been synthesized and fully characterized. The catalytic activity of 3a-3c in some C-C bond formation reactions has been examined. They are efficient catalysts for the homo-coupling of benzyl bromide in the presence of MeMgCl at r.t. with good functional group tolerance. Complex 3a is active in the catalytic oxidative homo-coupling of Grignard reagents with 1,2-dichloroethane as an oxidant at r.t.
Csp3-Csp3 homocoupling reaction of benzyl halides catalyzed by rhodium
Sato, Kazuyuki,Inoue, Yuichi,Mori, Tomohisa,Sakaue, Atsushi,Tarui, Atsushi,Omote, Masaaki,Kumadaki, Itsumaro,Ando, Akira
supporting information, p. 3756 - 3759 (2014/08/05)
A highly reactive alkylrhodium complex was formed from Me2Zn and RhCl(PPh3)3 and effectively catalyzed a Csp 3-Csp3 homocoupling reaction of benzyl halides. A Csp 3-Csp3 coupling reaction using Rh catalyst has not been reported up to now. The reaction proceeded under very mild conditions and gave the corresponding homocoupling products even if they had reactive substituents such as an uncovered formyl or hydroxymethyl group.
