765-42-4Relevant articles and documents
Iridium Azocarboxamide Complexes: Variable Coordination Modes, C-H Activation, Transfer Hydrogenation Catalysis, and Mechanistic Insights
Albold, Uta,Chandra, Shubhadeep,Hazari, Arijit Singha,Kelm, Ola,Ko?mrlj, Janez,Sarkar, Biprajit,Urankar, Damijana
supporting information, p. 3907 - 3916 (2021/12/03)
Azocarboxamides, a special class of azo ligands, display intriguing electronic properties due to their versatile binding modes and coordination flexibility. These properties may have significant implications for their use in homogeneous catalysis. In the present report, half-sandwich Ir-Cp? complexes of two different azocarboxamide ligands are presented. Different coordination motifs of the ligand were realized using base and chloride abstracting ligand to give N∧N-, N∧O-, and N∧C-chelated monomeric iridium complexes. For the azocarboxamide ligand having methoxy substituted at the phenyl ring, a mixture of N∧C-chelated mononuclear (Ir-5) and N∧N,N∧C-chelated dinuclear complexes (Ir-4) were obtained by activating the C-H bond of the aryl ring. No such C-H activation was observed for the ligand without the methoxy substituent. The molecular identity of the complexes was confirmed by spectroscopic analyses, while X-ray diffraction analyses further confirmed three-legged piano-stool structure of the complexes along with the above binding modes. All complexes were found to exhibit remarkable activity as precatalysts for the transfer hydrogenation of carbonyl groups in the presence of a base, even at low catalyst loading. Optimization of reaction conditions divulged superior catalytic activity of Ir-3 and Ir-4 complexes in transfer hydrogenation over the other catalysts. Investigation of the influence of binding modes on the catalytic activity along with wide range substrates, tolerance to functional groups, and mechanistic insights into the reaction pathway are also presented. These are the first examples of C-H activation in azocarboxamide ligands.
CuBr2-catalyzed ring opening/formylation reaction of cyclopropyl carbinols with DMF to synthesize formate esters
Zhuang, Daijiao,Gatera, Tharcisse,Yan, Rulong
supporting information, (2020/10/19)
An unprecedented protocol for the synthesis of formate esters has been developed by employing N,N-dimethylformamide (DMF) as both the source of CHO and solvent. This reaction undergoes ring opening of the cyclopropyl carbinols and in situ formation of homoallylic alcohols, which reacts with DMF to give the desired products. The substrate cyclopropyl carbinols with different groups participate smoothly in this process and the desired products are obtained in moderate to good yields.
σ-Bond Hydroboration of Cyclopropanes
Arifin,Itami, Kenichiro,Kato, Hiroki,Kobayashi, Chisa,Kondo, Hiroki,Matsushita, Kaoru,Miyamura, Shin,Yamaguchi, Junichiro,Yokogawa, Daisuke
supporting information, p. 11306 - 11313 (2020/07/13)
Hydroboration of alkenes is a classical reaction in organic synthesis in which alkenes react with boranes to give alkylboranes with subsequent oxidation resulting in alcohols. The double bond (π-bond) of alkenes can be readily reacted with boranes owing to its high reactivity. However, the single bond (σ-bond) of alkanes has never been reacted. To pursue the development of σ-bond cleavage, we selected cyclopropanes as model substrates since they present a relatively weak σ-bond. Herein, we describe an iridium-catalyzed hydroboration of cyclopropanes, resulting in β-methyl alkylboronates. These unusually branched boronates can be derivatized by oxidation or cross-coupling chemistry, accessing "designer"products that are desired by practitioners of natural product synthesis and medicinal chemistry. Furthermore, mechanistic investigations and theoretical studies revealed the enabling role of the catalyst.
Enantioselective Hydrogenation of Ketones using Different Metal Complexes with a Chiral PNP Pincer Ligand
Garbe, Marcel,Wei, Zhihong,Tannert, Bianca,Spannenberg, Anke,Jiao, Haijun,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
supporting information, p. 1913 - 1920 (2019/03/13)
The synthesis of different metal pincer complexes coordinating to the chiral PNP ligand bis(2-((2R,5R)-2,5-dimethyl-phospholanoethyl))amine is described in detail. The characterized complexes with Mn, Fe, Re and Ru as metal centers showed good activities regarding the reduction of several prochiral ketones. Comparing these catalysts, the non-noble metal complexes produced best selectivities not only for aromatic substrates, but also for different kinds of aliphatic ones leading to enantioselectivities up to 99% ee. Theoretical investigations elucidated the mechanism and rationalized the selectivity. (Figure presented.).
Cooperative Mn(i)-complex catalyzed transfer hydrogenation of ketones and imines
Ganguli, Kasturi,Shee, Sujan,Panja, Dibyajyoti,Kundu, Sabuj
, p. 7358 - 7366 (2019/06/06)
The synthesis and reactivity of Mn(i) complexes bearing bifunctional ligands comprising both the amine N-H and benzimidazole fragments are reported. Among the various ligands, the N-((1H-benzimidazol-2-yl)methyl)aniline ligand containing Mn(i) complex presented higher reactivity in the transfer hydrogenation (TH) of ketones in 2-propanol. Experimentally, it was established that both the benzimidazole and amine N-H proton played a vital role in the enhancement of the catalytic activity. Utilizing this system a wide range of aldehydes and ketones were reduced efficiently. Notably, the TH of several imines, as well as chemoselective reduction of unsaturated ketones, was achieved in the presence of this catalyst. DFT calculations were carried out to understand the plausible reaction mechanism which disclosed that the transfer hydrogenation reaction followed a concerted outer-sphere mechanism.
Efficient and Practical Transfer Hydrogenation of Ketones Catalyzed by a Simple Bidentate Mn?NHC Complex
van Putten, Robbert,Benschop, Joeri,de Munck, Vincent J.,Weber, Manuela,Müller, Christian,Filonenko, Georgy A.,Pidko, Evgeny A.
, p. 5232 - 5235 (2019/07/18)
Catalytic reductions of carbonyl-containing compounds are highly important for the safe, sustainable, and economical production of alcohols. Herein, we report on the efficient transfer hydrogenation of ketones catalyzed by a highly potent Mn(I)?NHC complex. Mn?NHC 1 is practical at metal concentrations as low as 75 ppm, thus approaching loadings more conventionally reserved for noble metal based systems. With these low Mn concentrations, catalyst deactivation is found to be highly temperature dependent and becomes especially prominent at increased reaction temperature. Ultimately, understanding of deactivation pathways could help close the activity/stability-gap with Ru and Ir catalysts towards the practical implementation of sustainable earth-abundant Mn-complexes.
Manganese N-Heterocyclic Carbene Complexes for Catalytic Reduction of Ketones with Silanes
Pinto, Mara,Fri?es, Sofia,Franco, Federico,Lloret-Fillol, Julio,Royo, Beatriz
, p. 2734 - 2740 (2018/07/24)
Well-defined manganese(I) carbonyl complexes bearing bis-N-heterocyclic carbene (NHC) ligands are shown to be effective catalysts for the reduction of carbonyl groups through hydrosilylation reactions. A wide variety of ketones are selectively reduced to the corresponding alcohols by using phenylsilane, and the cheap and readily abundant polymethylhydrosiloxane (PMHS) in the presence of catalytic amounts of MnI organometallic complexes. Interestingly, α,β-unsaturated ketones and dialkyl ketones are selectively reduced. Mechanistic studies based on radical scavengers suggest the involvement of radical species in the catalytic reaction.
Total Synthesis of ent-Pregnanolone Sulfate and Its Biological Investigation at the NMDA Receptor
Kapras, Vojtech,Vyklicky, Vojtech,Budesinsky, Milos,Cisarova, Ivana,Vyklicky, Ladislav,Chodounska, Hana,Jahn, Ullrich
supporting information, p. 946 - 949 (2018/02/23)
A unique asymmetric total synthesis of the unnatural enantiomer of pregnanolone, as well as a study of its biological activity at the NMDA receptor, is reported. The asymmetry is introduced by a highly atom-economic organocatalytic Robinson annulation. A new method for the construction of the cyclopentane D-ring consisting of CuI-catalyzed conjugate addition and oxygenation followed by thermal cyclization employing the persistent radical effect was developed. ent-Pregnanolone sulfate is surprisingly only 2.6-fold less active than the natural neurosteroid.
Constructing reactive Fe and Co complexes from isolated picolyl-functionalized N-heterocyclic carbenes
Liang, Qiuming,Liu, Nina Jiabao,Song, Datong
supporting information, p. 9889 - 9896 (2018/08/06)
We report the isolation of free picolyl-functionalized N-heterocyclic carbenes (NHCs), which serve as versatile precursors to access low coordinate iron and cobalt complexes. The reactivities of these new iron and cobalt complexes towards catalytic hydrosilylation of ketones have also been explored. For example, low loadings (0.05-1 mol%) of a four-coordinate iron complex bearing two deprotonated picolyl-NHC ligands can effect the fast catalytic reduction of ketones using the inexpensive industrial byproduct polymethylhydrosiloxane (PMHS) as the reductant at ambient temperature.
Hydrogenation of Carbonyl Derivatives Catalysed by Manganese Complexes Bearing Bidentate Pyridinyl-Phosphine Ligands
Wei, Duo,Bruneau-Voisine, Antoine,Chauvin, Téo,Dorcet, Vincent,Roisnel, Thierry,Valyaev, Dmitry A.,Lugan, No?l,Sortais, Jean-Baptiste
supporting information, p. 676 - 681 (2017/12/26)
Manganese(I) catalysts incorporating readily available bidentate 2-aminopyridinyl-phosphine ligands achieve a high efficiency in the hydrogenation of carbonyl compounds, significantly better than parent ones based on more elaborated and expensive tridentate 2,6-(diaminopyridinyl)-diphosphine ligands. The reaction proceeds with low catalyst loading (0.5 mol%) under mild conditions (50 °C) with yields up to 96%. (Figure presented.).
