1142-22-9Relevant articles and documents
Regio- and Stereoselective Diarylation of 1,3-Dienes via Ni/Cr Cocatalysis
Chen, Qing-An,Hu, Yan-Cheng,Ji, Ding-Wei,Li, Ying,Zhang, Wei-Song,Zhang, Xiang-Xin,Zhao, Chao-Yang
, p. 2158 - 2165 (2022/02/14)
Through the formation of the thermodynamically favored Cr(III)-O bond, the Nozaki-Hiyama-Kishi reaction has been widely applied in the functionalization of carbonyl compounds with the help of Ni catalysis. Herein, a divergent regio- and stereoselective diarylation of dienes has been developed under Ni/Cr cocatalysis without the inherent driving force for the formation of polar metal alkoxides. Preliminary experimental studies have been conducted to elucidate the key roles of Ni, Cr, and redox-active bis(imino)pyridine (PDI) ligands. The proposed mechanism suggests that the newly formed C-C bond of this diarylation was created by organonickel species instead of organochromium species.
Cationic Tungsten Imido Alkylidene N-Heterocyclic Carbene Complexes That Contain Bulky Ligands
Buchmeiser, Michael R.,Frey, Wolfgang,Musso, Janis V.,Schowner, Roman
, p. 3145 - 3157 (2021/09/30)
Neutral and cationic tungsten imido alkylidene complexes of the general formulas W(NtBu)(CHR1)(OR2)Cl(NHC), W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl2(NHC), [W(NtBu)(CHR1)(OR2)(NHC)][B(ArF)4] and [W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl(NHC)][B(ArF)4] (R1= CMe3, CMe2Ph; R2= sterically demanding alkoxide; B(ArF)4= tetrakis(3,5-(CF3)2-C6H3)borate; NHC = N-heterocyclic carbene) were prepared. Two electronically different NHCs, namely 1,3-dimethylimidazol-2-ylidene (IMe) and 1,3-dimethyl-4,5-dichloroimidazol-2-ylidene (IMeCl), as well as a variety of terphenolates and a chiral biphenolate were employed.Z-selective homometathesis (HM) of unfunctionalized olefins was achieved with a selectivity of up to 90% and decent turnover numbers (TON) of up to 480 in the HM of 1-dodecene. Additionally, the reactivity of the cationic tungstentert-butylimido complexes in the reaction with vinyltrimethylsilane and ethylene was investigated, which yielded the corresponding silyl-alkylidene complex and, for the first time, a fully characterized cationic tungsten(IV) NHC ethylene complex.
Continuous Flow Z-Stereoselective Olefin Metathesis: Development and Applications in the Synthesis of Pheromones and Macrocyclic Odorant Molecules**
Browne, Duncan L.,Colombel-Rouen, Sophie,Crévisy, Christophe,Curbet, Idriss,Mauduit, Marc,McBride, Tom,Morvan, Jennifer,Roisnel, Thierry
supporting information, p. 19685 - 19690 (2021/08/06)
The first continuous flow Z-selective olefin metathesis process is reported. Key to realizing this process was the adequate choice of stereoselective catalysts combined with the design of an appropriate continuous reactor setup. The designed continuous process permits various self-, cross- and macro-ring-closing-metathesis reactions, delivering products in high selectivity and short residence times. This technique is exemplified by direct application to the preparation of a range of pheromones and macrocyclic odorant molecules and culminates in a telescoped Z-selective cross-metathesis/ Dieckmann cyclisation sequence to access (Z)-Civetone, incorporating a serial array of continually stirred tank reactors.
Z-Selective Monothiolate Ruthenium Indenylidene Olefin Metathesis Catalysts
Smit, Wietse,Ekeli, Jonas B.,Occhipinti, Giovanni,Wo?niak, Bartosz,T?rnroos, Karl W.,Jensen, Vidar R.
, p. 397 - 407 (2020/02/13)
Ru-alkylidenes bearing sterically demanding arylthiolate ligands (SAr) constitute one of only two classes of catalyst that are Z-selective in metathesis of 1-alkenes. Of particular interest are complexes bearing pyridine as a stabilizing donor ligand, [RuCl(SAr)(a? CHR)(NHC)(py)] (R = phenyl or 2-thienyl, NHC = N-heterocyclic carbene, py = pyridine), which initiate catalysis rapidly and give appreciable yields combined with moderate to high Z-selectivity within minutes at room temperature. Here, we extend this chemistry by synthesizing and testing the first two such complexes (5a and 5b) bearing 3-phenylindenylidene, a ligand known to promote stability in other ruthenium-based olefin metathesis catalysts. The steric pressure resulting from the three bulky ligands (the NHC, the arylthiolate, and the indenylidene) forces the thiolate ligand to position itself trans to the NHC ligand, a configuration different from that of the corresponding alkylidenes. Surprisingly, although this configuration is incompatible with Z-selectivity and slows down pyridine dissociation, the two new complexes initiate readily at room temperature. Although their thermal stability is lower than that of typical indenylidene-bearing catalysts, 5a and 5b are fairly stable in catalysis (TONs up to 2200) and offer up to ca. 80% of the Z-isomer in prototypical metathesis homocoupling reactions. Density functional theory (DFT) calculations confirm the energetic cost of dissociating pyridine from 5a (= M1-Py) to generate 14-electron complex M1. Whereas the latter isomer does not give a metathesis-potent allylbenzene ?-complex, it may isomerize to M1-trans and M2, which both form ?-complexes in which the olefin is correctly oriented for cycloaddition. The olefin orientation in these complexes is also indicative of Z-selectivity.
Organoselenium-catalyzed enantioselective syn-dichlorination of unbiased alkenes
Gilbert, Bradley B.,Eey, Stanley T.-C.,Ryabchuk, Pavel,Garry, Olivia,Denmark, Scott E.
supporting information, p. 4086 - 4098 (2019/06/25)
The enantioselective dichlorination of alkenes is a continuing challenge in organic synthesis owing to the limitations of selective and independent antarafacial delivery of both electrophilic chlorenium and nucleophilic chloride to an olefin. Development of a general method for the enantioselective dichlorination of isolated alkenes would allow access to a wide variety of polyhalogenated natural products. Accordingly, the enantioselective suprafacial dichlorination of alkenes catalyzed by electrophilic organoselenium reagents has been developed to address these limitations. The evaluation of twenty-three diselenides as precatalysts for enantioselective dichlorination is described, with a maximum e.r. of 76:24 Additionally, mechanistic studies suggest an unexpected Dynamic Kinetic Asymmetric Transformation (DyKAT) process may be operative.
Monothiolate ruthenium alkylidene complexes with tricyclic fluorinated N-heterocyclic carbene ligands
Akmalov, Timur R.,Masoud, Salekh M.,Vorobyeva, Daria V.,Dolgushin, Fedor M.,Nefedov, Sergey E.,Osipov, Sergey N.
, p. 38 - 40 (2019/02/19)
New monothiolate ruthenium alkylidene complexes bearing bulky tricyclic N-heterocyclic carbene ligands decorated with two geminal trifluoromethyl groups were synthesized. Their catalytic activity in representative olefin metathesis reactions, such as ring closing metathesis of diallyltosylamine and selfmetathesis of allylbenzene, has been evaluated.
New olefin metathesis catalyst bearing N-mesitylimidazole and nitrate ligands – Synthesis, activity, and performance in aqueous media
Malinowska, Marta,Kozlowska, Mariana,Hryniewicka, Agnieszka,Morzycki, Jacek W.
, p. 154 - 161 (2019/06/24)
A new 18-electron ruthenium complex, where ruthenium catalytic center is coordinated with the N-mesitylimidazole and nitrate ligands, as well as o-isopropoxystyrene moiety, is reported. The synthesis and detailed characterization of the Ru complex, togeth
Design of bis-NHC Ru-complexes featuring diarylmethylene N-substituents for olefin metathesis
Curbet, Idriss,Morvan, Jennifer,Colombel-Rouen, Sophie,Roisnel, Thierry,Crévisy, Christophe,Mauduit, Marc
supporting information, p. 102 - 112 (2019/07/09)
New ruthenium indenylidene complexes containing N-heterocyclic carbene (NHC) ligands were synthesized and evaluated in olefin metathesis. The presence of two symmetrical saturated NHCs featuring N-diarylmethylene fragments (R= H, OMe or F) led to robust ruthenium precatalysts with a good latency. A kinetic study was investigated showing that a thermal stimulus (>60 °C) is required to reach an efficient catalytic initiation. Interestingly, a slight electronic effect was observed depending on the presence of an electron-donating or –withdrawing group within the diarylmethylene moiety. These complexes showed good activity at 1 mol% of catalyst loading in selected ring-closing metathesis (RCM) and cross-metathesis (CM) transformations.
Vanadium-Catalyzed Cross Metathesis: Limitations and Implications for Future Catalyst Design
Farrell, Wesley S.
supporting information, p. 3481 - 3485 (2019/11/13)
Self-metathesis of terminal olefins using vanadium(V) alkylidenes is presented. Under various reaction conditions, incomplete conversion is observed due to decomposition of the metallocyclobutane intermediate via β-hydride elimination. The activity was observed to decline when a more electron withdrawing, less sterically bulky ligand was used, in contrast to trends observed in ring-opening metathesis polymerization with vanadium catalysts. These results provide insight into the current limitations of olefin metathesis with vanadium catalysts, as well as guidance for catalyst development.
Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors
Polyanskii, Kirill B.,Alekseeva, Kseniia A.,Raspertov, Pavel V.,Kumandin, Pavel A.,Nikitina, Eugeniya V.,Gurbanov, Atash V.,Zubkov, Fedor I.
supporting information, p. 769 - 779 (2019/04/17)
A novel and efficient approach to the synthesis of 2-vinylbenzylamines is reported. This involves obtaining 2-vinylbenzylamine ligands from tetrahydroisoquinoline by alkylation and reduction followed by the Hofmann cleavage. The resultant 2-vinylbenzyl-amines allowed us to obtain new Hoveyda–Grubbs catalysts, which were thoroughly characterised by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10?2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM).
