- Effect of aryl ligand identity on catalytic performance of trineopentylphosphine arylpalladium complexes in n-arylation reactions
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A series of air-stable [(Np3P)Pd(Ar)Br]2 (Np = neopentyl) and (Np3P)Pd(Ar)(amine)Br complexes (amine = morpholine and isobutylamine) have been prepared and tested as precatalysts for the coupling of sterically demanding ar
- Hu, Huaiyuan,Burlas, Corrie E.,Curley, Sabrina J.,Gruchala, Tomasz,Qu, Fengrui,Shaughnessy, Kevin H.
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p. 3618 - 3627
(2020/11/03)
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- Flexible Steric Bulky Bis(Imino)acenaphthene (BIAN)-Supported N-Heterocyclic Carbene Palladium Precatalysts: Catalytic Application in Buchwald-Hartwig Amination in Air
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To achieve efficient palladium-catalyzed cross-coupling reaction under mild reaction conditions with the flexible steric bulk strategy, a series of Pd-PEPPSI (PEPPSI: pyridine-enhanced precatalyst preparation, stabilization, and initiation) complexes C1-C6 were synthesized and characterized, in which unsymmetric flexible steric bulk was introduced on the N-aryl of ancenaphthyl skeleton. These well-defined palladium complexes were found to be excellent precatalysts for Buchwald-Hartwig amination of aryl chlorides with amines in air. The electronic effect of the Pd-PEPPSI complexes and the effect of ancillary pyridine ligands were evaluated, among which complex C3 exhibited the most efficiency. It was demonstrated that the cross-coupling products were obtained in excellent yields in the presence of 0.5-0.1 mol % palladium loading. A wide range of aryl- and heteroaryl chlorides as well as various amines were compatible. The oxidative addition of aryl chlorides is revealed to be the rate-determining step in the catalytic cycle. The catalytic activity can be enhanced by introducing electron-donating groups to the Pd-PEPPSI complexes. This type of Pd-PEPPSI precatalyst showed the most efficiency reported to date for the challenging C-N cross-coupling reactions requiring no anhydrous and inert atmosphere protections, suggesting flexible steric bulk as a promising catalyst design strategy.
- Lan, Xiao-Bing,Li, Yinwu,Li, Yan-Fang,Shen, Dong-Sheng,Ke, Zhuofeng,Liu, Feng-Shou
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p. 2914 - 2925
(2017/03/23)
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- Trineopentylphosphine: A conformationally flexible ligand for the coupling of sterically demanding substrates in the Buchwald-Hartwig amination and suzuki-miyaura reaction
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Trineopentylphosphine (TNpP) in combination with palladium provides a highly effective catalyst for the Buchwald-Hartwig coupling of sterically demanding aryl bromides and chlorides with sterically hindered aniline derivatives. Excellent yields are obtain
- Raders, Steven M.,Moore, Jane N.,Parks, Jacquelynn K.,Miller, Ashley D.,Lei?ing, Thomas M.,Kelley, Steven P.,Rogers, Robin D.,Shaughnessy, Kevin H.
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p. 4649 - 4664
(2013/06/27)
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- A highly efficient precatalyst for amination of aryl chlorides: Synthesis, structure and application of a robust acenaphthoimidazolylidene palladium complex
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A robust palladium NHC complex was synthesized and exhibits exceptional activity and selectivity as a precatalyst in the amination of aryl chlorides and tolerates a wide range of substrates at low catalyst loadings.
- Tu, Tao,Fang, Weiwei,Jiang, Jian
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supporting information; experimental part
p. 12358 - 12360
(2011/12/15)
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- Nickel-catalyzed amination of aryl tosylates
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(Chemical Equation Presented) The cross-coupling of aryl tosylates with amines and anilines was accomplished by using a Ni-based catalyst system from the combination of Ni(II)-(σ-aryl) complexes/N-heterocyclic carbenes (NHCs). The feature, scope, and limitation of this reaction are disclosed.
- Gao, Cai-Yan,Yang, Lian-Ming
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p. 1624 - 1627
(2008/09/17)
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- (t-Bu)2PN=P(i-BuNCH2CH2)3N: New efficient ligand for palladium-catalyzed C-N couplings of aryl and heteroaryl bromides and chlorides and for vinyl bromides at room temperature
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(Chemical Equation Presented) By employing Pd(OAc)2, Cs 2CO3, or NaOH, and the new ligand (t-Bu) 2PN=P(i-BuNCH2CH2)3N (3a), an electronically diverse array of aryl bromides and chlorides possessing base-sensitive substituents (nitro, ester, and keto) provide coupling products with bulky aryl amines in good to excellent yields. Aryl halides possessing other functional groups including cyano, amino, trifluoromethyl, and phenol, coupled with equal ease, producing highly functionalized amines in good to excellent yields. Moreover, an aryl chloro group can be preserved in the presence of a bromo substituent under our reaction conditions. BOC-protected amines also participated efficiently. Heterocyclic bromides and chlorides underwent clean couplings with amines in excellent yields. An important strength of our protocol is the use of lower palladium loadings than those reported earlier, without compromising yields. The air-stable palladium complex (η3-cinnamyl)PdCl·(3a) (5) was also employed successfully in C-N coupling reactions while the crotyl analogue was less efficacious. The 3a/Pd(OAc)2 catalyst system promotes, for the first time, efficient coupling of vinyl bromides with a variety of amines to produce imines and enamines at room temperature.
- Reddy, Ch. Venkat,Kingston, Jesudoss V.,Verkade, John G.
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p. 3047 - 3062
(2008/09/19)
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- Facile synthesis and characterization of naphthidines as a new class of highly nonplanar electron donors giving robust radical cations
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Naphthidines 2 were prepared by nickel-catalyzed amination of 1-chloronaphthalene followed by oxidative homocoupling of 1-naphthalene amines 1 using titanium(IV) tetrachloride. The electronic and magnetic properties of materials 2 were investigated by cyclic voltammetry and other electrochemical techniques, EPR and UV-visible spectroscopies, and magnetic susceptibility. It was demonstrated that compounds 2 could be easily and reversibly oxidized via a two-electron-transfer reaction into their bis(radical cation) 22.2+, which displays a substantial stability at room temperature (the half-life of 22.2+ estimated by EPR at 25 °C was 10 days). B3LYP/6-31G* optimized structures of N,N′-bis(4-methoxyphenyl)-(1,1′-binaphthyl)- 4,4′-diamine 2g shows significant differences in the torsion angle between the naphthalene moieties depending on its oxidation state. Twisted structures are preferred for neutral compounds, whereas more planar are favored for the oxidized forms 2g+ and 2g2.2+ to realize spin and/or charge delocalizations over the whole π-system. Such conformation changes concerted with the electron transfers contribute to explain the unusual two-electron process observed in the electrochemical behavior of 2g instead of the two single-electron transfers that would have been expected in the case of two successive oxidations. It is finally shown that the oxidation of 2g in CH2Cl2 with thianthrenium perchlorate (ThClO4) generates the dication 2g2.2+ with singlet spin-multiplicity.
- Desmarets, Christophe,Champagne, Benoit,Walcarius, Alain,Bellouard, Christine,Omar-Amrani, Rafik,Ahajji, Abdelaziz,Fort, Yves,Schneider, Raphael
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p. 1351 - 1361
(2007/10/03)
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