- Oxo-Rhenium-Catalyzed Radical Addition of Benzylic Alcohols to Olefins
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Although carbon radicals generated from a variety of alcohol derivatives have proven valuable in coupling and addition reactions, the direct use of alcohols as synthetically useful radical sources is less known. In this report, benzylic alcohols are shown to be effective radical precursors for addition reactions to alkenes when treated with triphenylphosphine or piperidine with the catalyst ReIO2(PPh3)2 (I).
- Bandari, Chandrasekhar,Nicholas, Kenneth M.
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p. 3320 - 3327
(2020/03/23)
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- Catalytic, Enantioselective β-Protonation through a Cooperative Activation Strategy
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The NHC-catalyzed transformation of unsaturated aldehydes into saturated esters through an organocatalytic homoenolate process has been thoroughly studied. Leveraging a unique “Umpolung”-mediated β-protonation, this process has evolved from a test bed for homoenolate reactivity to a broader platform for asymmetric catalysis. Inspired by our success in using the β-protonation process to generate enals from ynals with good E/Z selectivity, our early studies found that an asymmetric variation of this reaction was not only feasible, but also adaptable to a kinetic resolution of secondary alcohols through NHC-catalyzed acylation. In-depth analysis of this process determined that careful catalyst and solvent pairing is critical for optimal yield and selectivity; proper choice of nonpolar solvent provided improved yield through suppression of an oxidative side reaction, while employment of a cooperative catalytic approach through inclusion of a hydrogen bond donor cocatalyst significantly improved enantioselectivity.
- Wang, Michael H.,Barsoum, David,Schwamb, C. Benjamin,Cohen, Daniel T.,Goess, Brian C.,Riedrich, Matthias,Chan, Audrey,Maki, Brooks E.,Mishra, Rama K.,Scheidt, Karl A.
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p. 4689 - 4702
(2017/05/12)
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- Vanadium(V)-Induced Oxidative Cross-Coupling of Various Boron and Silyl Enolates
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Intermolecular oxidative cross-coupling of two different enolates is one of the most useful reactions to synthesize unsymmetrical 1,4-dicarbonyl compounds. In this study, the oxovanadium(V)-induced intermolecular oxidative cross-coupling of enolates afforded unsymmetrical 1,4-dicarbonyl compounds. Various boron and silyl enolates underwent the formation of ketone–ester, ester–ketone, ester–ester, amide–ketone and amide–ester coupling products. These results clearly show the versatility of the present oxidative cross-coupling protocol.
- Amaya, Toru,Osafune, Yuma,Maegawa, Yusuke,Hirao, Toshikazu
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p. 1301 - 1304
(2017/06/23)
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- Enantioselective β-Protonation by a Cooperative Catalysis Strategy
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An enantioselective N-heterocyclic carbene (NHC)-catalyzed β-protonation through the orchestration of three distinct organocatalysts has been developed. This cooperative catalyst system enhances both yield and selectivity, compared to only the NHC-catalyz
- Wang, Michael H.,Cohen, Daniel T.,Schwamb, C. Benjamin,Mishra, Rama K.,Scheidt, Karl A.
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p. 5891 - 5894
(2015/05/27)
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- First pre-functionalised polymeric aromatic framework from mononitrotetrakis(iodophenyl)methane and its applications
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Starting from mononitrotetrakis(iodophenyl)methane as monomer, we report the preparation of the first pre-functionalised porous aromatic frameworks (PAFs) and their application as supports for organometallic catalysts. Neutral coordinate imino-pyridine Schiff base (PAF-NPy) or chiral bis-amino (PAF-NPro) ligands were obtained by post-synthetic treatment of PAF-NH2 and treated with copper(I) or rhodium(I) to yield the corresponding supported transition-metal catalysts. The as-prepared PAF-NN-M catalysts exhibited activity and selectivity similar to that of the corresponding homogeneous catalysts and were easily removed from reaction media and recycled without loss of activity or selectivity. New copper catalysts: The preparation of pre-functionalised porous aromatic frameworks (PAFs) and their application as supports for organometallic catalysts (see figure) is reported for the first time.
- Verde-Sesto, Ester,Pintado-Sierra, Mercedes,Corma, Avelino,Maya, Eva M.,De La Campa, Jose G.,Iglesias, Marta,Sanchez, Felix
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supporting information
p. 5111 - 5120
(2014/05/06)
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- Development of homogeneous and heterogenized rhodium(i) and palladium(ii) complexes with ligands based on a chiral proton sponge building block and their application as catalysts
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Chiral compounds prepared from proton sponge building block 8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-1-amine were found to be effective chiral ligands for obtaining complexes of rhodium(i) and palladium(ii) by reaction with [RhCl(cod)]2, PdCl2(cod) or Pd(OAc) 2. The complexes bearing triethoxysilane groups were immobilized on mesoporous MCM-41 in order to obtain new heterogeneous catalysts. Both materials are active in the hydrogenation of alkenes and could be recycled without loss of activity or enantioselectivity.
- Villaverde, Gonzalo,Arnanz, Avelina,Iglesias, Marta,Monge, Angeles,Sanchez, Felix,Snejko, Natalia
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scheme or table
p. 9589 - 9600
(2011/11/13)
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- Rh-catalyzed asymmetric hydroformylation of functionalized 1,1-disubstituted olefins
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The first method for the highly enantioselective rhodium-catalyzed hydroformylation of 1,1-disubstituted olefins has been developed. By employing either of the P-chirogenic phosphine ligands BenzP* and QuinoxP*, linear aldehydes with β-chirality can be prepared in a highly enantioselective fashion with good chemo- and regioselectivities.
- Wang, Xiao,Buchwald, Stephen L.
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supporting information; experimental part
p. 19080 - 19083
(2012/01/05)
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- Immobilization of (NHC)NN-pincer complexes on mesoporous MCM-41 support
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Unsymmetrical pincer-type-ligated {pincer = [C6H 3N(CH2L1)(CH2L2)-2,6], L1 = prolinamide, L2 = NHC} gold and rhodium complexes have proven to be highly effective catalysts for the hydrogenation of alkenes. Immobilization on ordered mesoporous silica (MCM-41) using a grafting process offers significant potential advantages in the application of such catalysts particularly with respect to catalyst separation and recycling. We describe one approach toward such immobilization: covalent bonding to silica via a pendant alkoxysilane group. This approach yields catalysts that are robust, recyclable, and comparable to or even more active than the corresponding species in solution. Spectroscopic evidence (IR spectroscopy, solid-state CP/MAS NMR, SEM), elemental analysis, and studies of catalytic activity support the hypothesis that binding occurs at the prolinamide substituent with no complex degradation. Control experiments showed the true heterogeneous nature of the catalyst in this reaction. Analyses of the hybrid materials revealed that the mesoporous structure of these materials was retained during the immobilization process as well as during catalysis.
- Del Pozo, Carolina,Corma, Avelino,Iglesias, Marta,Sanchez, Felix
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experimental part
p. 4491 - 4498
(2011/01/09)
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- New chiral ligands bearing two N-heterocyclic carbene moieties at a dioxolane backbone. Gold, palladium and rhodium complexes as enantioselective catalysts
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Biscarbene ligands with two imidazolin-2-ylidene moieties at a chiral dioxolane backbone were used as ligands for gold, rhodium and palladium complexes. All new complexes showed varying degrees of enantioselectivity toward hydrogenation of prochiral alkenes with ees up to 95%. The Royal Society of Chemistry 2010.
- Arnanz, Avelina,Gonzalez-Arellano, Camino,Juan, Alberto,Villaverde, Gonzalo,Corma, Avelino,Iglesias, Marta,Sanchez, Felix
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experimental part
p. 3001 - 3003
(2010/08/04)
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- Synthesis of electron-rich CNN-pincer complexes, with N-heterocyclic carbene and (S)-proline moieties and application to asymmetric hydrogenation
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New chiral CNN-pincer-type gold, palladium, and rhodium complexes containing N-heterocyclic carbene substituent and (S)-N-tert-butyl- methylpyrrolidine-2-carboxamide as chiral auxiliary have been synthesized and studied for asymmetric hydrogenation. The complexes were prepared by the silver carbene transfer route from the respective silver complex. The reaction with [RhCl(cod)]2 (cod = cycloocta-l,5-diene), PdCl2(CH 3CN)2, or K[AuCl4] affords the corresponding cationic [Rh(cod)(ligand)]Cl, [PdCl(ligand)]Cl, and [AuCl(ligand)]Cl2 complexes in which the ligand functions effectively in a CNN coordination mode. The complexes catalyze the enantioselective hydrogenation of prochiral alkenes. Enantioselectivity is very sensitive to the NHC N-substituent, resulting in a useful switch in the predominant enantiomer.
- Boronat, Merce,Corma, Avelino,Gonzalez-Arellano, Camino,Iglesias, Marta,Sanchez, Felix
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experimental part
p. 134 - 141
(2010/03/03)
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- New pyridine ONN-pincer gold and palladium complexes: Synthesis, characterization and catalysis in hydrogenation, hydrosilylation and C-C cross-coupling reactions
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The ONN-tridentate unsymmetrical pincer 2-[6-(pyrrolidin-1-ylmethyl) pyridin-2-yl]phenol and N-terf-butyl-1-{[6-(2-hydroxyphenyl)pyridin-2-yi] metriyl}pyrrolidine-2-carboxamide ligands were synthesized by an easy method in high purity and good yields. All the organic compounds were characterized by elemental analysis, mass spectrometry, IR and 1H and 13C NMR spectroscopy. Palladium(II) and gold(III) complexes have been prepared as air-stable solids, with the ONN-tridentate ligand after deprotonation of the hydroxy group, the coordination of the metal ion is completely stereospecific and gives rise to only one diastereoisomer. These complexes were shown to be very active catalysts in the hydrogenation (80 % ee was achieved with the chiral gold complex), hydrosilylation and C-C coupling, Suzuki and Heck, reactions, under mild conditions.
- Debono,Iglesias,Sanchez
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p. 2470 - 2476
(2008/09/19)
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- New heterogenized gold(I)-heterocyclic carbene complexes as reusable catalysts in hydrogenation and cross-coupling reactions
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Mononuclear unsymmetrical N-heterocyclic carbene-gold complexes and the corresponding solid catalysts in which a gold-carbene complex has been immobilized on silica gel, ordered mesoporous silica (MCM-41), and delaminated zeolite (ITQ-2) have been prepared. These new catalysts have been tested in the hydrogenation of alkenes and the Suzuki cross-coupling reaction to afford selectively non-symmetrical biaryls. These reactions were studied with the soluble as well as with the heterogenized counterpart catalysts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs up to 400 h-1. Moreover, the heterogenized complexes were reused and no deactivation of the catalysts can be observed.
- Corma,Gutierrez-Puebla,Iglesias,Monge,Perez-Ferreras,Sanchez
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p. 1899 - 1907
(2007/10/03)
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- Enantioselective hydrogenation of alkenes and imines by a gold catalyst
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A new neutral dimeric gold(I) complex bearing the 1,2-bis[(2R,5A)-2,5- dimethylphospholanebenzene] [(R,R)-Me-Duphos] ligand has been synthesized which catalyzes the asymmetric hydrogenation of alkenes and imines under mild reaction conditions. The Royal Society of Chemistry 2005.
- Gonzalez-Arellano, Camino,Corma, Avelino,Iglesias, Marta,Sanchez, Felix
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p. 3451 - 3453
(2007/10/03)
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- Improved palladium and nickel catalysts heterogenised on oxidic supports (Silica, MCM-41, ITQ-2, ITQ-6)
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Two series of solid catalysts in which a chiral palladium or nickel complex with Schiff bases as ligands have been immobilized on ordered mesoporous silica supports (MCM-41), delaminated ITQ-2, ITQ-6 zeolites and amorphous silica have been prepared. Hydrogenation of alkenes and imines was studied with the homogeneous as well as with the counterpart heterogenized catalysts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs of 1,000,000 h -1. A moderate acidity in the support increases the catalytic activity considerably, and the easy recoverable immobilized catalysts can duplicate the activity of the homogeneous analogues. No deactivation of the catalysts was observed after repeated recycling.
- Gonzalez-Arellano,Corma,Iglesias,Sanchez
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p. 1316 - 1328
(2007/10/03)
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- Therapeutic substituted indole compounds and compositions thereof
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The present invention is concerned with compounds of formula (I) STR1 wherein R, R1 and R2 are independently selected from hydrogen and C1-4 alkyl; R3 and R4 are independently selected from hydrogen, C1-6 alkyl (including cycloalkyl) and aryl (wherein the alkyl or aryl group, which latter includes benzyl, is optionally substituted by one or more atoms or groups independently selected from halogen, C1-4 alkyl and aryl), provided R3 benzyl or substituted benzyl when R4 =H; m is an integer of from 0 to 2; n is an integer of from 0 to 3; (W) is a group of formula (i), (ii), (iii), or (iv) STR2 wherein Y is selected from oxygen, methylene and >N--R5, where R5 is hydrogen, C1-4 alkyl, or benzyl, Z and Z' are independently selected from >C=O, >C=S and methylene, and the chiral center * in formula (i) or (ii) is in its (S) or (R) form or is a mixture thereof in any proportions; X is a group selected from aryl (including heteroaryl) xanthenyl dibenzofuranyl which group is optionally substituted; and salts and solvates thereof, the preparation of these compounds, pharmaceutical formulations containing them and their use in medicine, particularly in the treatment of migraine.
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