- 1,3-Dipolar cycloaddition reactivities of perfluorinated aryl azides with enamines and strained dipolarophiles
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The reactivities of enamines and predistorted (strained) dipolarophiles toward perfluoroaryl azides (PFAAs) were explored experimentally and computationally. Kinetic analyses indicate that PFAAs undergo (3 + 2) cycloadditions with enamines up to 4 orders of magnitude faster than phenyl azide reacts with these dipolarophiles. DFT calculations were used to identify the origin of this rate acceleration. Orbital interactions between the cycloaddends are larger due to the relatively low-lying LUMO of PFAAs. The triazolines resulting from PFAA-enamine cycloadditions rearrange to amidines at room temperature, while (3 + 2) cycloadditions of enamines and phenyl azide yield stable, isolable triazolines. The 1,3-dipolar cycloadditions of norbornene and DIBAC also show increased reactivity toward PFAAs over phenyl azide but are slower than enamine-azide cycloadditions.
- Xie, Sheng,Lopez, Steven A.,Ramstr?m, Olof,Yan, Mingdi,Houk
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supporting information
p. 2958 - 2966
(2015/03/18)
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- Visible light-induced intermolecular radical addition: Facile access to γ-ketoesters from alkyl-bromocarboxylates and enamines
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A highly efficient addition of alkyl α-bromocarboxylates to enamines by visible light-induced photoredox catalysis is reported. Compared with traditional methods, the reaction described here provided an alternative route for the construction of valuable γ-ketoesters in generally good yields.
- Hu, Bei,Chen, Haixia,Liu, Yan,Dong, Wuheng,Ren, Kai,Xie, Xiaomin,Xu, Hao,Zhang, Zhaoguo
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p. 13547 - 13550
(2015/01/09)
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- Kinetics and thermodynamics of H-/H?/H+ transfer from a rhodium(III) hydride
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The thermodynamics and kinetics of all three cleavage modes for Rh-H, the transfer of H-, H+, or H?, have been studied for the Rh(III) hydride complex Cp*Rh(2-(2-pyridyl)phenyl)H (1a). The thermodynamic hydricity, ΔG°H-, for 1a has been measured (49.5(1) kcal/mol) by heterolytic cleavage of H2 with Et3N in CH3CN. The transfer of H- from 1a to 1-(1-phenylethylidene)pyrrolidinium is remarkably fast (k H- = 3.5(1) × 105 M-1 s -1), making 1a a very efficient catalyst for the ionic hydrogenation of iminium cations. The pKa of 1a in CH3CN has been measured as 30.3(2) with (tert-butylimino)tris(pyrrolidino)phosphorane (12), and the rate constant for H+ transfer from 1a to 12 has been estimated (kH+ = 5(1) × 10-4 M-1 s -1) from the half-life of the equilibration. Thus, 1a is a poor H+ donor both thermodynamically and kinetically. However, 1a transfers H? to TEMPO smoothly, forming a stable Rh(II) radical Cp*Rh(2-(2-pyridyl)phenyl)? (14a) that can activate H2 at room temperature and 1 atm. The metalloradical 14a has a g value of 2.0704 and undergoes reversible one-electron reduction at -1.85 V vs Fc+/Fc in benzonitrile, implying a bond-dissociation enthalpy for the Rh-H bond of 1a of 58.2(3) kcal/mol-among the weakest Rh(III)-H bonds reported. The transfer of H? from 1a to Ar3C? (Ar = p-tBuC 6H4) is fast, with kH? = 1.17(3) × 103 M-1 s-1. Thus, 1a is a good H- and H? donor but a poor H+ donor, a combination that reflects the high energy of the Rh(I) anion [Cp*Rh(2-(2-pyridyl)phenyl)] -.
- Hu, Yue,Norton, Jack R.
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p. 5938 - 5948
(2014/05/20)
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- Structure and dynamic behavior of phosphine gold(I)-coordinated enamines: Characterization of α-metalated iminium ions
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Cationic gold(I) enamine complexes with the (t-Bu)2(o-biphenyl) phosphine ligand were isolated and characterized by NMR spectroscopy and X-ray crystallography. The complexes display highly distorted coordination modes that are consistent with characterization as α-metalated iminium ions. The barrier to rotation around the formal enamine C-C double bond has been measured in a geminally disubstituted enamine complex, and it is comparable to the barrier to C-C single-bond rotation in electronically restricted alkanes. With additional substitution on the enamine double bond, the complexes remain highly distorted, and the reaction of a mixture of E and Z enamines results in formation of a stereochemically pure gold complex. A survey of binding constants reveals enamines to be significantly stronger donors than any alkenes examined to date, and in the case of a geminally disubstituted enamine, the coordination is stronger even than that of triethylamine. The high stability drives the isomerization of an internal enamine complex generated from an intramolecular hydroamination reaction, to the exocyclic double-bond isomer.
- Sriram, Madhavi,Zhu, Yuyang,Camp, Andrew M.,Day, Cynthia S.,Jones, Amanda C.
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supporting information
p. 4157 - 4164
(2014/11/26)
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- A cationic gold(I) complex as a general catalyst for the intermolecular hydroamination of alkynes: Application to the one-pot synthesis of allenes from two alkynes and a sacrificial amine
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A cationic gold (I) complex was reported to catalyze the addition of various types of non-tertiary amines to terminal and internal alkynes. The one-pot preparation of allenes by coupling two alkynes using a sacrificial secondary amine was also investigate
- Zeng, Xiaoming,Frey, Guido D.,Kousar, Shazia,Bertrand, Guy
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supporting information; experimental part
p. 3056 - 3060
(2009/11/30)
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- GOLD CATALYZED HYDROAMINATION OF ALKYNES AND ALLENES
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Methods are provided for the catalytic hydroamination of compounds having an alkyne or allene functional group, in which the compound is contacted with ammonia or an amine in the presence of a catalytic amount of a gold complex under conditions sufficient for hydroamination to occur.
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Page/Page column 26; 6/13
(2010/01/29)
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- Asymmetrie copper-catalyzed propargylic substitution reaction of propargylic acetates with enamines
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Enamines served as carbon-nucleophiles for the first time In the Cu-catalyzed asymmetric propargylic substitution reaction of propargylic acetates, providing corresponding chiral β-ethynyl-substituted ketones In high yields and In good to high enantioselectivity.
- Fang, Ping,Hou, Xue-Long
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supporting information; experimental part
p. 4612 - 4615
(2009/12/09)
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- A polymer-bound oxidovanadium(IV) complex prepared from an L-cysteine-derived ligand for the oxidative amination of styrene
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The ligand H2sal-cys (I) derived from salicylaldehyde and Lcysteine has been covalently bonded to chloromethylated polystyrene cross-linked with 5% divinylbenzene. Upon treatment with [VO(acac)2] in dimethylformamide (DMF) the polystyrene-bound ligand PS-H2sal-cys (II) gave the oxidovanadium(IV) complex, PS-[VO(sal-cys)·DMF] (1). The corresponding neat complex, [VO(sal-eta)]2 (2), has also been prepared similarly in methanol. These complexes have been characterised by IR, electronic, EPR spectroscopic studies, magnetic susceptibility measurements and thermal as well as scanning electron micrographs studies. Complex [VO-(sal-eta)]2 exhibits a medium intensity band at 980 cm -1 in the IR spectrum due to ν(V=O) stretch. Broad features of the EPR spectrum for the neat complex along with magnetic susceptibility studies suggest the presence of antiferromagnetic exchange interaction between two vanadium centers in close proximity. Both complexes catalyze the oxidative amination of styrene, in mild basic conditions, with secondary amines (diethylamine, imidazole, and benzimidazole) and gave a mixture of two aminated products in good yields. Amongst the two aminated products, the anti-Markovnikov product is favored over the Markovnikov one due to the steric hindrance posed by the secondary amines. The polymeranchored heterogeneous catalyst is free from leaching during catalytic action and recyclable. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Maurya, Mannar R.,Kumar,Correia, Isabel,Adao, Pedro,Pessoa, Joao Costa
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p. 577 - 587
(2008/12/22)
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- New reaction of enamines with aryldiazoacetates catalyzed by transition metal complexes
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The reaction of aryldiazoacetates with enamines catalyzed by copper and rhodium complexes provided γ-keto esters in good yields. A full investigation of the effects of solvents, catalysts, enamines and aryldiazoacetates on the reaction was carried out. Careful analysis of the crude reaction mixture revealed a substituted enamine as the primary product, which was hydrolyzed over silica gel to give a γ-keto ester as the final product. A reaction mechanism involving nucleophilic addition of an enamine to a metal carbene and subsequent hydrogen transfer was proposed. Chiral dirhodium and copper catalysts were examined and found to provide γ-keto esters with no enantioselectivity. The result could be rationalized based on the proposed reaction mechanism. Attempts to trap the enamine intermediate with several electrophilic reagents were not successful.
- Zhao, Wei-Jie,Yan, Ming,Huang, Dan,Ji, Shun-Jun
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p. 5585 - 5593
(2007/10/03)
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- SYNTHESIS OF α-DIALKYLAMINOSTYRENES AND THEIR REACTION WITH AZODICARBOXYLIC ESTER AND COMPOUNDS CONTAINING AN ACTIVATED MULTIPLE BOND
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Lower α-dialkylaminostyrenes react with compounds containing an activated double bond by a mechanism of "vinyl" substitution with the formation of both disubstituted and monosubstituted compounds.The ester groups of the mono- and bisN,N'-di(methoxycarbon
- Koikov, L. N.,Terent'ev, P. B.,Torochesnikov, V. N.,Kulikov, N. S.
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p. 110 - 118
(2007/10/02)
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