- Catalytic hydrogenation of α,β-unsaturated carboxylic acid derivatives using copper(i)/N-heterocyclic carbene complexes
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A simple and air-stable copper(i)/N-heterocyclic carbene complex enables the catalytic hydrogenation of enoates and enamides, hitherto unreactive substrates employing homogeneous copper catalysis and H2 as a terminal reducing agent. This atom economic transformation replaces commonly employed hydrosilanes and can also be carried out in an asymmetric fashion.
- Zimmermann, Birte M.,Kobosil, Sarah C. K.,Teichert, Johannes F.
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supporting information
p. 2293 - 2296
(2019/02/27)
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- NON-IONIC BLOCK COPOLYMERS AND PHARMACEUTICAL COMPOSITIONS DERIVED THEREFROM
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There are provided PVP-PLA block copolymers as defined in Formula (I): I wherein, x is an initiator alcohol having a boiling point greater than 145°C, n is, on average, from 20 and 40, and m is, on average, from 10 and 40, wherein the block copolymers hav
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- Cross-metathesis reaction of functionalized and substituted olefins using group 8 transition metal carbene complexes as metathesis catalysts
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The invention pertains to the use of Group 8 transition metal carbene complexes as catalysts for olefin cross-metathesis reactions. In particular, ruthenium and osmium alkylidene complexes substituted with an N-heterocyclic carbene ligand are used to catalyze cross-metathesis reactions to provide a variety of substituted and functionalized olefins, including phosphonate-substituted olefins, directly halogenated olefins, 1,1,2-trisubstituted olefins, and quaternary allylic olefins. The invention further provides a method for creating functional diversity using the aforementioned complexes to catalyze cross-metathesis reactions of a first olefinic reactant, which may or may not be substituted with a functional group, with each of a plurality of different olefinic reactants, which may or may not be substituted with functional groups, to give a plurality of structurally distinct olefinic products. The methodology of the invention is also useful in facilitating the stereoselective synthesis of 1,2-disubstituted olefins in the cis configuration.
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- Oxygen-atom insertion of NHCecopper complex: The source of oxygen from N, N-dimethylformamide
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An unprecedented protocol for oxygen-atom insertion reaction of NHCecopper complexes has been developed by employing N,N-dimethylformamide as the oxygen source, which allows the preparation of imidazolinones from carbene complexes and decodes one of the m
- Zeng, Wei,Wang, Enyu,Qiu, Rui,Sohail, Muhammad,Wu, Shaoxiang,Chen, Fu-Xue
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supporting information
p. 44 - 48
(2013/10/08)
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- PKas of the conjugate acids of N-heterocyclic carbenes in water
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pKa values of 19.8-28.2 are reported for the conjugate acids of a large series of NHCs in water. The effects of ring size, N-substituent and C(4)-C(5) saturation on pKa are discussed.
- Higgins, Eleanor M.,Sherwood, Jennifer A.,Lindsay, Anita G.,Armstrong, James,Massey, Richard S.,Alder, Roger W.,O'Donoghue, Annmarie C.
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supporting information; experimental part
p. 1559 - 1561
(2011/03/22)
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- Tuning the electronic properties of N-heterocyclic carbenes
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The electron-donating properties of N-heterocyclic carbenes ([N,N′-bis(2,6-dimethylphenyl)imidazol]-2-ylidene and the respective dihydro ligands) with 4,4′-R-substituted aryl rings (4,4′-R = NEt2, OC12H25, Me, H, Br, S(4-t
- Leuthaeusser, Steffen,Schwarz, Daniela,Plenio, Herbert
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p. 7195 - 7203
(2008/03/12)
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- Synthesis and activity of ruthenium alkylidene complexes coordinated with phosphine and N-heterocyclic carbene ligands
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This paper reports the synthesis and characterization of a variety of ruthenium complexes coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several alkylidene derivatives of the general formula (NHC)(PR3)(Cl)2Ru=CHR′, which are highly active olefin metathesis catalysts. Although these catalysts can be prepared adequately by the reaction of bis(phosphine) ruthenium alkylidene precursors with free NHCs, we have developed an alternative route that employs NHC-alcohol or -chloroform adducts as "protected" forms of the NHC ligands. This route is advantageous because NHC adducts are easier to handle than their free carbene counterparts. We also demonstrate that sterically bulky bis(NHC) complexes can be made by reaction of the pyridine-coordinated precursor (NHC)(py)2(Cl)2Ru=CHPh with free NHCs or NHC adducts. Two crystal structures are presented, one of the mixed bis(NHC) derivative (H2IMes)(IMes)(Cl)2Ru=CHPh, and the other of (PCy3)(Cl)(CO)Ru[η2-(CH2- C6H2Me2)(N2 C3H4)(C6H2Me3)], the product of ortho methyl C-H bond activation. Other side reactions encountered during the synthesis of new ruthenium alkylidene complexes include the formation of hydridocarbonyl-chloride derivatives in the presence of primary alcohols and the deprotonation of ruthenium vinylcarbene ligands by KOBut. We also evaluate the olefin metathesis activity of NHC-coordinated complexes in representative RCM and ROMP reactions.
- Trnka, Tina M.,Morgan, John P.,Sanford, Melanie S.,Wilhelm, Thomas E.,Scholl, Matthias,Choi, Tae-Lim,Ding, Sheng,Day, Michael W.,Grubbs, Robert H.
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p. 2546 - 2558
(2007/10/03)
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- Imidazolylidenes, imidazolinylidenes and imidazolidines
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Starting from glyoxal, 1,3-diarylimidazolinium chlorides 3 were obtained in a three-step sequence via the diimines (1) and ethylene diamine dihydrochlorides (2). Reduction of 1,3-diarylimidazolinium chlorides (3) with lithium alumnium hydride furnished the 1,3- diarylimidazolidines (4) while their deprotonation with potassium hydride in thf gave access to stable carbenes (1,3-diarylimidazolin-2-ylidenes, 5). Similarly substituted imidazol-2-ylidenes are described for comparison.
- Arduengo III, Anthony J.,Krafczyk, Roland,Schmutzler, Reinhard,Craig, Hugh A.,Goerlich, Jens R.,Marshall, William J.,Unverzagt, Markus
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p. 14523 - 14534
(2007/10/03)
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