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41.
Dr. Bo Liu Dr. Thierry Roisnel Prof. Dr. Jean‐François Carpentier Dr. Yann Sarazin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(40):13445-13462
[{N^N}M(X)(thf)n] alkyl (X=CH(SiMe3)2) and amide (X=N(SiMe3)2) complexes of alkaline earths (M=Ca, Sr, Ba) and divalent rare earths (YbII and EuII) bearing an iminoanilide ligand ({N^N}?) are presented. Remarkably, these complexes proved to be kinetically stable in solution. X‐ray diffraction studies allowed us to establish size–structure trends. Except for one case of oxidation with [{N^N}YbII{N(SiMe3)2}(thf)], all these complexes are stable under the catalytic conditions and constitute effective precatalysts for the cyclohydroamination of terminal aminoalkenes and the intermolecular hydroamination and intermolecular hydrophosphination of activated alkenes. Metals with equal sizes across alkaline earth and rare earth families display almost identical apparent catalytic activity and selectivity. Hydrocarbyl complexes are much better catalyst precursors than their amido analogues. In the case of cyclohydroamination, the apparent activity decreases with metal size: Ca>Sr>Ba, and the kinetic rate law agrees with RCHA=k[precatalyst]1[aminoalkene]1. The intermolecular hydroamination and hydrophosphination of styrene are anti‐Markovnikov regiospecific. In both cases, the apparent activity increases with the ionic radius (Ca<Sr<Ba) but the rate laws are different, and obey RHA=k[styrene]1[amine]1[precatalyst]1 and RHP=k[styrene]1[HPPh2]0[precatalyst]1, respectively. Mechanisms compatible with the rate laws and kinetic isotopic effects are proposed. [{N^N}Ba{N(SiMe3)2}(thf)2] ( 3 ) and [{N^N}Ba{CH(SiMe3)2}(thf)2] ( 10 ) are the first efficient Ba‐based precatalysts for intermolecular hydroamination and hydrophosphination, and display activity values that are above those reported so far. The potential of the precatalysts for C? N and C? P bond formation is detailed and a rare cyclohydroamination–intermolecular hydroamination “domino” sequence is presented. 相似文献
42.
Andreas Uhe Dr. Markus Hölscher Prof. Dr. Walter Leitner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(3):1020-1027
Very few cases of oxidative addition of NH3 to transition‐metal complexes forming terminal amide hydrides have been experimentally observed. Here, two examples with the iridium pincer complexes [Ir(PCP)(NH3)] A1 with PCP=[κ3‐(tBu2P‐C2H4)2CH]? and [Ir(PSiP)(NH3)] B1 with PSiP=[κ3‐(2‐Cy2P‐C6H4)2SiMe]? were investigated by DFT calculations applying the M06L density functional to successfully reproduce the trend of the experimentally observed thermochemical stabilities. According to the calculations, the corresponding hydrido‐amido complexes A2 and B2 are more stable than the corresponding ammine complexes by ΔG=?2.8 and ?2.6 kcal mol?1, respectively. Complexes such as A2 and B2 are ideally suited entry points to catalytic cycles for the hydroamination of ethylene with ammonia. Therefore, the relevant stationary points of the potentially available cycles were studied computationally to verify if these complexes can catalyze the hydroamination. As a result, complex A2 will clearly not catalyze the hydroamination as all energy spans calculated range close to 40 kcal mol?1 or higher. The energy spans obtained with B2 are significantly lower in some cases and range around 35 kcal mol?1, further indicating that no turnover can be expected. By systematically varying the structure of B2 , the energy span could be reduced to 28.8 kcal mol?1 corresponding to a TOF of 17 h?1 at a reaction temperature of 140 °C. A reoptimization of relevant structures under the inclusion of cyclohexane as a typical solvent reduces the calculated TOF to 6.0 h?1. 相似文献
43.
Rsuini U. Gutirrez Mayra Hernndez-Montes Aarn Mendieta-Moctezuma Francisco Delgado Joaquín Tamariz 《Molecules (Basel, Switzerland)》2021,26(13)
An efficient synthesis of ketimines was achieved through a regioselective Hg(I)-catalyzed hydroamination of terminal acetylenes in the presence of anilines. The Pd(II)-catalyzed cyclization of these imines into the 2-substituted indoles was satisfactorily carried out by a C-H activation. In a single-step approach, a variety of 2-substituted indoles were also generated via a Hg(I)/Pd(II)-catalyzed, one-pot, two-step process, starting from anilines and terminal acetylenes. The arylacetylenes proved to be more effective than the alkyl derivatives. 相似文献
44.
Jielin Zhang Eleonora Grandi Haigen Fu Thangavelu Saravanan Laura Bothof Pieter G. Tepper Andy‐Mark W. H. Thunnissen Gerrit J. Poelarends 《Angewandte Chemie (International ed. in English)》2020,59(1):429-435
Aspartic acid derivatives with branched N‐alkyl or N‐arylalkyl substituents are valuable precursors to artificial dipeptide sweeteners such as neotame and advantame. The development of a biocatalyst to synthesize these compounds in a single asymmetric step is an as yet unmet challenge. Reported here is an enantioselective biocatalytic synthesis of various difficult N‐substituted aspartic acids, including N‐(3,3‐dimethylbutyl)‐l ‐aspartic acid and N‐[3‐(3‐hydroxy‐4‐methoxyphenyl)propyl]‐l ‐aspartic acid, precursors to neotame and advantame, respectively, using an engineered variant of ethylenediamine‐N,N′‐disuccinic acid (EDDS) lyase from Chelativorans sp. BNC1. This engineered C–N lyase (mutant D290M/Y320M) displayed a remarkable 1140‐fold increase in activity for the selective hydroamination of fumarate compared to that of the wild‐type enzyme. These results present new opportunities to develop practical multienzymatic processes for the more sustainable and step‐economic synthesis of an important class of food additives. 相似文献
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46.
《Comptes Rendus Chimie》2016,19(5):614-629
The treatment of [PdL3(NH3)](OTf)n (n = 1; L3 = (PEt3)2(Ph), (2,6-(Cy2PCH2)2C6H3), n = 2; L3 = (dppe)(NH3)) with NaNH2 in tetrahydrofuran at ambient temperature or −78 °C afforded the dimeric and monomeric parent-amido palladium(II) complexes anti-[Pd(PEt3)(Ph)(μ-NH2)]2 (1), [Pd(dppe)(μ-NH2)]2(OTf)2 (2), and Pd(2,6-(Cy2PCH2)2C6H3)(NH2) (3), respectively. The molecular structures of the amido-bridged (μ-NH2) dimeric complexes 1 and 2 were determined by single-crystal X-ray crystallography. The monomeric amido complex 3 reacted with trace amounts of water to give a hydroxo complex, Pd(2,6-(Cy2PCH2)2C6H3)(OH) (4). Exposing complex 3 to an excess of water resulted in the complete conversion of the complex into two species [Pd(2,6-(Cy2PCH2)2C6H3)(OH2)]+ and [Pd(2,6-(Cy2PCH2)2C6H3)(NH3)]+. Complex 3 reacted with diphenyliodonium triflate ([Ph2I]OTf) to give the aniline complex [Pd(2,6-(Cy2PCH2)2C6H3)(NH2Ph)]OTf. The reaction of 3 with phenylacetylene (HCCPh) yielded a palladium(II) acetylenide Pd(2,6-(Cy2PCH2)2C6H3)(CCPh) (5), quantitatively, along with the liberation of ammonia. The reaction of 3 with dialkyl acetylenedicarboxylate yielded diastereospecific palladium(II) vinyl derivatives (Z)-Pd(2,6-(Cy2PCH2)2C6H3)(CRCR(NH2)) (R = CO2Me (6a), CO2Et (6b)). The reaction of complexes 6a and 6b with p-nitrophenol produced Pd(2,6-(Cy2PCH2)2C6H3)(OC6H4-p-NO2) (7) and cis-CHRCR(NH2), exclusively. Reactions of 3 with either dialkyl maleate (cis-(CO2R)CHCH(CO2R)) (R = CH3, CH2CH3) or cis-stilbene (cis-CHPhCHPh) did not result in any addition product. Instead, isomerization of the cis-isomers to the trans-isomers occurred in the presence of catalytic amounts of 3. Complex 3 reacted with a stoichiometric amount of acrylonitrile (CH2CHCN) to generate a metastable insertion product, Pd(2,6-(Cy2PCH2)2C6H3)(CH(CN)CH2NH2). On the other hand, the reaction of 3 with an excess of acrylonitrile slowly produced polymeric species of acrylonitrile. The catalytic hydroamination of olefins with NH3 was examined in the presence of Pd(2,6-(Cy2PCH2)2C6H3)(OTf), producing a range of hydroaminated products of primary, secondary, and tertiary amines with different molar ratios of more than 99% overall yield. A mechanistic feature for the observed catalytic hydroamination is described with regard to the aminated derivatives of palladium(II). 相似文献
47.
Dochnahl M Löhnwitz K Pissarek JW Biyikal M Schulz SR Schön S Meyer N Roesky PW Blechert S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(23):6654-6666
A series of symmetrical and unsymmetrical N,N'-disubstituted aminotroponimines (ATIHs) have been prepared. Substituents ranging from linear to cyclic alkyl groups, chelating ethers, and aryl groups were employed. The corresponding aminotroponiminate zinc complexes were then synthesized and characterized by a number of techniques, including by X-ray crystallography. Herein we report on the investigations into their activity in the intramolecular hydroamination of nonactivated alkenes. We also demonstrate that complexes bearing ligands with cyclic alkyl groups show superior activity in a number of selected reactions with functionalized aminoalkenes. 相似文献
48.
Tobisch S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(32):9127-9136
The regulation of ring-substituent diastereoselectivity in the intramolecular hydroamination/cyclisation (IHC) of alpha-substituted aminodienes by constrained geometry CGC-lanthanide catalysts (CGC=[Me(2)Si(eta(5)-Me(4)C(5))(tBuN)](2-)) has been elucidated by means of a reliable DFT method. The first survey of relevant elementary steps for the 1-methyl-(4E,6)-heptadienylamine substrate (1) and the [{Me(2)Si(eta(5)-Me(4)C(5))(tBuN)}Sm{N(TMS)(2)}] starting material (2) identified the following general mechanistic aspects of Ln-catalysed aminodiene IHC. The substrate-adduct 3-S of the active CGC-Ln-amidodiene compound represents the catalyst's resting state, but the substrate-free form 3' with a chelating amidodiene functionality is the direct precursor for cyclisation. This step proceeds with almost complete regioselectivity through exocyclic ring closure by means of a frontal trajectory, giving rise to the CGC-Ln-azacycle intermediate 4. Subsequent protonolysis of 4 is turnover limiting, whilst the ring-substituent diastereoselectivity is dictated by exocyclic ring closure. Unfavourable close interatomic contacts between the substrate's alpha-substituent and the catalyst backbone have been shown to largely govern the trans/cis selectivity. Substituents of sufficient bulk in the alpha-position of the substrate have been identified as being vital for stereochemical induction. The present study has indicated that the diastereoselectivity of ring closure can be considerably modulated. The variation of the lanthanide's ionic radius and introduction of extra steric pressure at the substrate's alpha-position and/or the CGC N centre have been identified as effective handles for tuning the selectivity. The quantification of these factors reported herein represents the first step toward the rational design of improved CGC-Ln catalyst architectures and will thus aid this process. 相似文献
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50.
T. O. Petersen E. Tausch Dr. J. Schaefer Dr. H. Scherer Prof.Dr. P. W. Roesky Prof.Dr. I. Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13696-13702
Ion‐like ethylzinc(II) compounds with weakly coordinating aluminates [Al(ORF)4]? and [(RFO)3Al‐F‐Al(ORF)3]? (RF=C(CF3)3) were synthesized in a one‐pot reaction and fully characterized by single‐crystal X‐ray diffraction, NMR and vibrational spectroscopy, and by quantum chemical calculations. The catalytic activity of ion‐like Et‐Zn[Al(ORF)4] in intermolecular hydroamination and in the unusual double hydroamination of anilines and alkynes was investigated. Favorable performance was also found in comparison to the Et2Zn/ [PhNMe2H]+[B(C6F5)4]? system generated in situ at lower catalyst loadings of 2.5 mol %. 相似文献