Synthesis of NHC-Oxazoline Pincer Complexes of Rh and Ru and Their Catalytic Activity for Hydrogenation and Conjugate Reduction

Ito, Junichi; Sugino, Kanae; Matsushima, Satoru; Sakaguchi, Hiroki; Iwata, Hiroshi; Ishihara, Takahiro; Nishiyama, Hisao

doi:10.1021/acs.organomet.6b00239

Cited by 24 publications

(18 citation statements)

References 89 publications

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“…In spite of the loss of p-cymene moiety, the mechanism of ATH probably involved, also in this case, a classical catalytic cycle. [37][38][39][40] Taking into consideration the differences in both structural coordination mode, our complexes resulted less active and straightly less stereoselective in comparison with other similar catalytic systems reported in literature. 16,35,[41][42] In those systems better results might depend on the presence of an additive in formation of bimetallic 6-membered transition state or in alternative on the presence of an additional phosphine ligand known for reducing the acidity of metal center that favors the hydride transfer.…”

Section: N-(3r4r)-3-[(s)-2-(aminomethyl)pyrrolidin-1-yl]-1-benzylpipmentioning

confidence: 57%

“…Furthermore, the results obtained with our complexes, indicated that the steric hindrance around the Ru center in the transition state, deriving both from the ligand and the substrate, could affect the reactivity and the enantioselectivity of the reactions. 27,37 In summary, the best result in terms of reaction rate and enantioselectivity was obtained with complex A in the reduction of the activated ketone substrate 4f, ethyl 3-oxo-3phenylpropanoate (entry 22).…”

Section: N-(3r4r)-3-[(s)-2-(aminomethyl)pyrrolidin-1-yl]-1-benzylpipmentioning

confidence: 99%

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Ruthenium(II) complexes bearing (NNN) ligand: catalytic evaluation of different solvent-mediated coordination modes

et al. 2018

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A new (NNN) tridentate ligand was prepared, and its ability to coordinate ruthenium(II) was evaluated. The presence of different functional groups on the ligand allows bi- or tri-coordinated complexes to be obtained depending on complexation conditions. The catalytic activity of both bidentate and tridentate complexes was studied in asymmetric transfer hydrogenation of different aryl ketones, showing a comparable behavior of the two complexes in terms of efficiency and stereoselectivity.

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Section: N-(3r4r)-3-[(s)-2-(aminomethyl)pyrrolidin-1-yl]-1-benzylpipmentioning

confidence: 57%

Section: N-(3r4r)-3-[(s)-2-(aminomethyl)pyrrolidin-1-yl]-1-benzylpipmentioning

confidence: 99%

Ruthenium(II) complexes bearing (NNN) ligand: catalytic evaluation of different solvent-mediated coordination modes

et al. 2018

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“…These results suggest that further development of these mixed-carbene-oxazoline systems could be useful for the selective reduction of extended aromatic-ring-systems. 204 …”

Section: Mono(oxazoline) Ligandsmentioning

confidence: 99%

Further Developments and Applications of Oxazoline-Containing Ligands in Asymmetric Catalysis

et al. 2021

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The chiral oxazoline motif is present in many ligands that have been extensively applied in a series of important metal-catalyzed enantioselective reactions. This Review aims to provide a comprehensive overview of the most significant applications of oxazoline-containing ligands reported in the literature starting from 2009 until the end of 2018. The ligands are classified not by the reaction to which their metal complexes have been applied but by the nature of the denticity, chirality, and donor atoms involved. As a result, the continued development of ligand architectural design from mono(oxazolines), to bis(oxazolines), to tris(oxazolines) and tetra(oxazolines) and variations thereof can be more easily monitored by the reader. In addition, the key transition states of selected asymmetric transformations will be given to illustrate the features that give rise to high levels of asymmetric induction. As a further aid to the reader, we summarize the majority of schemes with representative examples that highlight the variation in % yields and % ee s for carefully selected substrates. This Review should be of particular interest to the experts in the field but also serve as a useful starting point to new researchers in this area. It is hoped that this Review will stimulate both the development/design of new ligands and their applications in novel metal-catalyzed asymmetric transformations.

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“…To avoid decarbonylation, employment of carbonyl Ru catalysts has been investigated. , In the past decade, monocarbonyl ruthenium complexes have been successfully applied in a number of organic reactions, such as TH and HY of carbonyl compounds, HY of carboxylic and carbonic acid derivatives, alcohol dehydrogenation, and C–X (X = C, N) forming reactions . Relevant examples of monocarbonyl catalysts are [Ru(TFA) 2 (PPh 3 ) 2 (CO)], [Ru(μ-OCOC 2 F 4 OCO)(diphosphine)(CO)] 2 , [Ru(OAc)(CCN)(CO)], Ru(CNO)(PPh 3 ) 2 (CO)], [RuCl 2 (NNN)(CO)] and [RuCl(NNN)(HOCH 3 )(CO)]Cl, and those reported by Milstein ([RuH(PNN)(CO)]), Gusev ([RuCl 2 (PNN)(CO)]), and Saito ([RuHCl(PNN)(CO)]) . Moreover, we have described that the derivatives [RuCl((2-CH 2 -6-MeC 6 H 3 )PPh 2 )(NN)(CO)] and [RuH(Ph 2 P(CH 2 ) 3 PPh 2 )(NN)(CO)]Cl (NN = en, ampy) are active in ketone TH reactions.…”

Section: Introductionmentioning

confidence: 99%

Flat and Efficient HCNN and CNN Pincer Ruthenium Catalysts for Carbonyl Compound Reduction

et al. 2019

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The bidentate HCNN dicarbonyl ruthenium complexes trans,cis-[RuCl2(HCNN)(CO)2] (1–3) and trans,cis-[RuCl2(ampy)(CO)2] (1a) were prepared by reaction of [RuCl2(CO)2] n with 1-[6-(4′-methylphenyl)pyridin-2-yl]methanamine, benzo[h]quinoline (HCNN), and 2-(aminomethyl)pyridine (ampy) ligands. Alternatively, the derivatives 1–3 were obtained from the reaction of RuCl3 hydrate with HCO2H and HCNN. The pincer CNN cis-[RuCl(CNN)(CO)2] (4) was isolated from 1 by reaction with NEt3. The monocarbonyl complexes trans-[RuCl2(HCNN)(PPh3)(CO)] (5–7) were synthesized from [RuCl2(dmf)(PPh3)2(CO)] and HCNN ligands, while the diacetate trans-[Ru(OAc)2(HCNN)(PPh3)(CO)] (8) was obtained from [Ru(OAc)2(PPh3)2(CO)]. Carbonylation of cis-[RuCl(CNN)(PPh3)2] with CO afforded the pincer derivatives [RuCl(CNN)(PPh3)(CO)] (9–11). Treatment of 9 with Na[BArf]4 and PPh3 gave the cationic complex trans-[Ru(CNN)(PPh3)2(CO)][BArf 4] (12). The dicarbonyl derivatives 1–4, in the presence of PPh3 or PCy3, and the monocarbonyl complexes 5–12 catalyzed the transfer hydrogenation (TH) of acetophenone (a) in 2-propanol at reflux (S/C = 1000–100000 and TOF up to 100000 h–1). Compounds 1–3, with PCy3, and 6 and 8–10 were proven to catalyze the TH of carbonyl compounds, including α,β-unsaturated aldehydes and bulky ketones (S/C and TOF up to 10000 and 100000 h–1, respectively). The derivatives 1–3 with PCy3 and 5 and 6 catalyzed the hydrogenation (HY) of a (H2, 30 bar) at 70 °C (S/C = 2000–10000). Complex 5 was active in the HY of diaryl ketones and aryl methyl ketones, leading to complete conversion at S/C = 10000.

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Synthesis of NHC-Oxazoline Pincer Complexes of Rh and Ru and Their Catalytic Activity for Hydrogenation and Conjugate Reduction

Cited by 24 publications

References 89 publications

Ruthenium(II) complexes bearing (NNN) ligand: catalytic evaluation of different solvent-mediated coordination modes

Ruthenium(II) complexes bearing (NNN) ligand: catalytic evaluation of different solvent-mediated coordination modes

Further Developments and Applications of Oxazoline-Containing Ligands in Asymmetric Catalysis

Flat and Efficient HCNN and CNN Pincer Ruthenium Catalysts for Carbonyl Compound Reduction

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