- Folding Assessment of Incorporation of Noncanonical Amino Acids Facilitates Expansion of Functional-Group Diversity for Enzyme Engineering
-
Protein design is limited by the diversity of functional groups provided by the canonical protein ?building blocks“. Incorporating noncanonical amino acids (ncAAs) into enzymes enables a dramatic expansion of their catalytic features. For this, quick identification of fully translated and correctly folded variants is decisive. Herein, we report the engineering of the enantioselectivity of an esterase utilizing several ncAAs. Key for the identification of active and soluble protein variants was the use of the split-GFP method, which is crucial as it allows simple determination of the expression levels of enzyme variants with ncAA incorporations by fluorescence. Several identified variants led to improved enantioselectivity or even inverted enantiopreference in the kinetic resolution of ethyl 3-phenylbutyrate.
- Drienovská, Ivana,Gajdo?, Matú?,Kindler, Alexia,Takhtehchian, Mahsa,Darnhofer, Barbara,Birner-Gruenberger, Ruth,D?rr, Mark,Bornscheuer, Uwe T.,Kourist, Robert
-
-
Read Online
- Rhodium-catalyzed conjugated addition of aryllead reagents to α,β-unsaturated carbonyl compounds in air and water
-
In the presence of a rhodium catalyst, α,β-unsaturated esters and ketones (1a-f) react with phenyltrimethyllead 2 in aqueous media and under an air atmosphere to give the corresponding conjugated addition products (3a-e) in high yields.
- Ding,Chen,Wang,Li
-
-
Read Online
- Chiral Phosphinopyrrolyl-Oxazolines: A New Class of Easily Prepared, Modular P,N-Ligands
-
Chiral 2-(N-phosphinopyrrol-2-yl)oxazolines (PyrPHOX ligands) are readily prepared from 2-cyanopyrrole by condensation with a chiral amino alcohol and subsequent reaction with dialkyl- or diaryl-chlorophosphines. Iridium complexes of these ligands proved to be highly efficient catalysts for the enantioselective hydrogenation of olefins. With unfunctionalized arylalkenes and ethyl cinnamate enantiomeric excesses of 70-99% were obtained.
- Cozzi, Pier Giorgio,Zimmermann, Nicole,Hilgraf, Robert,Schaffner, Silvia,Pfaltz, Andreas
-
-
Read Online
- Alteration of enzyme activity and enantioselectivity by biomimetic encapsulation in silica particles
-
Direct encapsulation of esterase or lipase fused with the silica-precipitating R5 peptide from Cylindrotheca fusiformis in silica particles afforded high yields of active entrapped protein. The hydrolytic activity of both enzymes against p-nitrophenyl butyrate was similarly affected by encapsulation and the enantioselectivity of the esterase was both improved and inverted. The Royal Society of Chemistry 2012.
- Emond, Stephane,Guieysse, David,Lechevallier, Severine,Dexpert-Ghys, Jeannette,Monsan, Pierre,Remaud-Simeon, Magali
-
-
Read Online
- Ir/Thioether-Carbene, -Phosphinite, and -Phosphite Complexes for Asymmetric Hydrogenation. A Case for Comparison
-
We studied for the first time the potential of novel and simple Ir/thioether-NHC complexes in the asymmetric hydrogenation of unfunctionalized olefins and cyclic β-enamides. For comparison, we prepared and applied the analogues thioether-phosphinite/phosphite complexes. We found that the efficiency of the new Ir/thioether-NHC catalyst precursors varies with the type of olefin. Thus, while the Ir/thioether-NHC catalyst precursors provided lower catalytic performance than their related Ir/thioether-P complexes in the hydrogenation of olefins lacking a coordinating group, the catalysts had similar good performance for the reduction of functionalized olefins (e.g., tri- and disubstituted enol phosphonate derivatives). Catalytic results together with the studies of the reactivity toward H2 indicated that the thioether-carbene design favors the formation of inactive trinuclear species, which are responsible for the low activities obtained with these carbene-type catalysts. Nevertheless, this catalyst deactivation can be avoided by using functionalized olefins such as enol phosphonates. We also report the discovery of simple-to-synthesize Ir/thioether-P catalysts containing a simple backbone that gave high enantioselectivities for some trisubstituted olefins, some challenging 1,1′-disubstituted olefins, and cyclic β-enamides.
- Cruz-Sánchez, Pol De La,Faiges, Jorge,Mazloomi, Zahra,Borràs, Carlota,Biosca, Maria,Pàmies, Oscar,Diéguez, Montserrat
-
-
Read Online
- Chiral (iminophosphoranyl)ferrocenes: Highly efficient ligands for rhodium- and iridium-catalyzed enantioselective hydrogenation of unfunctionalized olefins
-
A series of chiral (iminophosphoranyl)ferrocenes (1-3) are highly efficient ligands for Rh- and Ir-catalyzed hydrogenation of a number of unfunctionalized olefins; almost perfect enantiomeric excesses (up to 99% ee) have been achieved under mild reaction conditions. The Royal Society of Chemistry 2006.
- Co, Thanh Thien,Kim, Tae-Jeong
-
-
Read Online
- Recent advances in iridium-catalyzed asymmetric hydrogenation: New catalysts, substrates and applications in total synthesis
-
Iridium-catalyzed asymmetric hydrogenation has emerged as a highly efficient method for the synthesis of enantiomerically pure compounds. This account summarizes our recent efforts in this field. We have developed a new type of P,O-ligand that was success
- Ganic, Adnan,Rageot, Denise,Troendlin, Lars,Pfaltz, Andreas
-
-
Read Online
- Chiral bis(N-tosylamino)phosphine- and TADDOL-phosphite-oxazolines as ligands in asymmetric catalysis
-
A series of P,N-ligands containing a chiral oxazoline ring and a chiral bis(N-tosylamino)phosphine group derived from a 1,2-diamine or a chiral cyclic phosphite group derived from TADDOL has been prepared. These compounds proved to be efficient ligands for enantiocontrol of palladium-catalyzed allylic alkylations and iridium-catalyzed hydrogenations of olefins.
- Hilgraf, Robert,Pfaltz, Andreas
-
-
Read Online
- Efficient preparation of new rhodium- and iridium-[bis(oxazolinyl)-3,5- dimethylphenyl] complexes by C-H bond activation: Applications in asymmetric synthesis
-
The bis(oxazolinyl)-3,5-dimethylphenylrhodium and -iridium complexes were synthesized in high yields by an efficient C-H bond activation method with 4,6-dimethyl-1,3-bis(oxazolinyl)benzene derivatives. The catalytic activity of the complexes was examined
- Ito, Jun-Ichi,Shiomi, Takushi,Nishiyama, Hisao
-
-
Read Online
- Enantioselective hydrogenation of olefins with planar chiral iridium ferrocenyloxazolinylphosphine complexes
-
Chiral iridium Fc-PHOX complexes were readily prepared from Fc-PHOX, [Ir(cod)Cl]2 and NaBArF (or NaPF6) in high yields. They were applied as catalysts in the enantioselective hydrogenation of olefins to afford the corresponding produ
- Li, Xinsheng,Li, Qing,Wu, Xiaohua,Gao, Yongguang,Xu, Dongcheng,Kong, Lichun
-
-
Read Online
- π-π Chelation controlled chemoselective conjugate addition of lithium dimethylcuprate
-
The conjugate addition of Me2CuLi to ethyl cinnamate derivatives bearing an alkynyl group at the ortho-position, took place preferentially in the presence of the corresponding α,β-unsaturated esters bearing an alkynyl group at the distal position or having no alkynyl groups. The observed chemoselectivity is most probably a reflection of the π-π chelation between π-electrons of the olefinic moiety of the enoates and those of the C-C triple bond located at the proximal position.
- Asao, Naoki,Lee, Sunyoung,Yamamoto, Yoshinori
-
-
Read Online
- Rhodium-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Carbonyl Compounds via Thiourea Hydrogen Bonding
-
The strategy of secondary interaction enables enantioselectivity for homogeneous hydrogenation. By introducing hydrogen bonding of substrates with thiourea from the ligand, α,β-unsaturated carbonyl compounds, such as amides and esters, are hydrogenated wi
- Wen, Jialin,Jiang, Jun,Zhang, Xumu
-
-
Read Online
- Copper-Catalyzed Enantioselective Formation of C?CF3 Centers from β-CF3-Substituted Acrylates and Acrylonitriles
-
The catalytic asymmetric synthesis of β-trifluoromethylated esters or nitriles is reported. The use of an in situ formed chiral Cu?H complex allowed the enantioselective reduction of β-trifluoromethylated acrylates or acrylonitriles. The reaction proceeds
- Poutrel, Pauline,Ivanova, Maria V.,Pannecoucke, Xavier,Jubault, Philippe,Poisson, Thomas
-
-
Read Online
- Iridium-Catalyzed Enantioselective Hydrogenation of Olefins
-
Cationic iridium complexes with chiral P,N-ligands and tetrakis[3,5- (trifluoromethyl)phenyl]borate (BArF) as the counterion are efficient homogeneous catalysts for the enantioselective hydrogenation of olefins. The complexes are readily prepared, air-sta
- Pfaltz, Andreas,Blankenstein, J?rg,Hilgraf, Robert,H?rmann, Esther,McIntyre, Steven,Menges, Frederik,Sch?nleber, Marc,Smidt, Sebastian P.,Wüstenberg, Bettina,Zimmermann, Nicole
-
-
Read Online
- Chiral pyranoside phosphite-oxazolines: A new class of ligand for asymmetric catalytic hydrogenation of alkenes
-
We have described the first successful application of a phosphite-oxazoline ligand library in the asymmetric Ir-catalyzed hydrogenation of several unfunctionalized olefins. The introduction of a bulky biaryl phosphite moiety in the ligand design is highly adventitious in the product outcome. By carefully selecting the ligand components, we obtained high activities (TOFs up to >1500 mol·(mol·h)-1 at 1 bar of H2) and enantioselectivities (ee values up to >99%) and, at the same time, show a broad scope for different substrate types. So, this is an exceptional ligand class that competes favorably with a few other ligand series that also provide high ee values for tri- and disubstituted substrate types. Copyright
- Dieguez, Montserrat,Mazuela, Javier,Pamies, Oscar,Verendel, J. Johan,Andersson, Pher G.
-
-
Read Online
- N-benzylpiperidinol derivatives as novel USP7 inhibitors: Structure–activity relationships and X-ray crystallographic studies
-
USP7 as a deubiquitinase plays important roles in regulating the stability of some oncoproteins including MDM2 and DNMT1, and thus represents a potential anticancer target. Through comparative analysis of USP7 co-crystal structures in complex with the rep
- Chen, Caiping,Chen, Hui,Cheng, Keguang,Li, Minglei,Liu, Jun,Liu, Shengjie,Sun, Hongbin,Wang, Yue,Wen, Xiaoan,Xu, Qing-Long,Yuan, Haoliang,Zhou, Jin,Zhou, Shuxi,Zhou, Xinyu
-
-
Read Online
- Asymmetrie hydrogenation of imines and olefins using phosphine-oxazoline iridium complexes as catalysts
-
Herein we describe the synthesis of a new class of chiral phosphine-oxazolines and their application as ligands in iridium-catalyzed hydrogenations. Mechanistic aspects of olefin hydrogenation with this class of iridium catalysts are discussed and a selec
- Trifonova, Anna,Diesen, Jarle S.,Andersson, Pher G.
-
-
Read Online
- Enantioselective hydrogenation of olefins with axial chiral iridium QUINAP complex
-
(S)-QUINAP reacted with [Ir(cod)Cl]2 to form a new chelating iridium complex in 77.4% yield. The iridium complex was proved to be a highly efficient catalyst for the enantioselective hydrogenation of olefins. 33.4-95.1% ee were obtained for the hydrogenation of unfunctionalized olefins and 90.8-96.1% ee were obtained for functionalized olefins.
- Li, Xinsheng,Kong, Lichun,Gao, Yongguang,Wang, Xiaoxia
-
-
Read Online
- A novel alkaline esterase from sporosarcina sp. nov. strain eSP04 catalyzing the hydrolysis of a wide variety of aryl-carboxylic acid esters
-
A novel esterase showing activity specific for esters of aryl-carboxylic acids was discovered in Sporosarcina sp. nov., which was identified by the 16S rDNA sequencing method in addition to morphological and physiological analyses. The aryl-carboxylesterase (named EstAC) was purified 780-fold from crude cell extracts by a 5-step procedure. EstAC was characterized as a monomeric protein with a molecular weight of 43,000, an optimum pH of around 9.0, and an optimum temperature of 40 °C. The pH optimum and the effects of inhibitors together with an internal amino acid sequence suggested that EstAC is a member of family VIII esterases. EstAC was found to be highly active on a wide variety of substrates such as alkyl benzoates, alkyl phenylacetates, ethyl α- or β-substituted phenylpropionates, dialkyl terephthalates, dimethyl isophthalate, and ethylene glycol dibenzoate. However, monomethyl terephthalate was not hydrolyzed. It was suggested that EstAC had 4-hydroxybenzoyl and cinnamoyl esterase activities as well.
- Takehara, Munenori,Kinoshita, Kaori,Miyamoto, Masahiro,Hirohara, Hideo
-
-
Read Online
- Chemical, pharmacological, and in vitro metabolic stability studies on enantiomerically pure RC-33 compounds: Promising neuroprotective agents acting as σ1 receptor agonists
-
Our recent research efforts identified racemic RC-33 as a potent and metabolically stable σ1 receptor agonist. Herein we describe the isolation of pure RC-33 enantiomers by chiral chromatography, assignment of their absolute configuration, and
- Rossi, Daniela,Pedrali, Alice,Gaggeri, Raffaella,Marra, Annamaria,Pignataro, Luca,Laurini, Erik,DalCol, Valentina,Fermeglia, Maurizio,Pricl, Sabrina,Schepmann, Dirk,Wuensch, Bernhard,Peviani, Marco,Curti, Daniela,Collina, Simona
-
-
Read Online
- Impact of solvent polarity on n-heterocyclic carbene-catalyzed β-protonations of homoenolate equivalents
-
N-Heterocyclic carbenes have been demonstrated to react through divergent pathways under the same conditions. Experimental and computational evidence demonstrates that the ability to favor generation of homoenolate equivalents from α,β-unsaturated aldehyd
- Maki, Brooks E.,Patterson, Eric V.,Cramer, Christopher J.,Scheidt, Karl A.
-
-
Read Online
- SimplePHOX, a readily available chiral ligand system for iridium-catalyzed asymmetric hydrogenation
-
Equation presented. New Ir-SimplePHOX complexes Ir-6-Ir-9 catalyze the quantitative, highly enantioselective hydrogenation of a range of unfunctionalized and functionalized olefins. Synthesis, catalytic results, and X-ray crystal structures are presented
- Smidt, Sebastian P.,Menges, Frederik,Pfaltz, Andreas
-
-
Read Online
- Monohydride-Dichloro Rhodium(III) Complexes with Chiral Diphosphine Ligands as Catalysts for Asymmetric Hydrogenation of Olefinic Substrates
-
We report full details of the synthesis and characterization of monohydride-dichloro rhodium(III) complexes bearing chiral diphosphine ligands, such as (S)-BINAP, (S)-DM-SEGPHOS, and (S)-DTBM-SEGPHOS, producing cationic triply chloride bridged dinuclear rhodium(III) complexes (1 a: (S)-BINAP; 1 b: (S)-DM-SEGPHOS) and a neutral mononuclear monohydride-dichloro rhodium(III) complex (1 c: (S)-DTBM-SEGPHOS) in high yield and high purity. Their solid state structure and solution behavior were determined by crystallographic studies as well as full spectral data, including DOSY NMR spectroscopy. Among these three complexes, 1 c has a rigid pocket surrounded by two chloride atoms bound to the rhodium atom together with one tBu group of (S)-DTBM-SEGPHOS for fitting to simple olefins without any coordinating functional groups. Complex 1 c exhibited superior catalytic activity and enantioselectivity for asymmetric hydrogenation of exo-olefins and olefinic substrates. The catalytic activity of 1 c was compared with that of well-demonstrated dihydride species derived in situ from rhodium(I) precursors such as [Rh(cod)Cl]2 and [Rh(cod)2]+[BF4]? upon mixing with (S)-DTBM-SEGPHOS under dihydrogen.
- Higashida, Kosuke,Brüning, Fabian,Tsujimoto, Nagataka,Higashihara, Kenya,Nagae, Haruki,Togni, Antonio,Mashima, Kazushi
-
-
Read Online
- Tandem Peterson olefination and chemoselective asymmetric hydrogenation of β-hydroxy silanes
-
Here, we report the first Ir-N,P complex catalyzed tandem Peterson olefination and asymmetric hydrogenation of β-hydroxy silanes. This reaction resulted in the formation of chiral alkanes in high isolated yields (up to 99%) and excellent enantioselectivity (up to 99% ee) under mild conditions. Modification of the reaction conditions provides a choice to transform either an olefin or the β-hydroxy silane in a chemoselective manner. Additionally, based on this method, an expedient enantioselective synthesis of (S)-(+)-α-curcumene, from a simple ketone, was accomplished in two steps with 75% overall yield and 95% ee.
- Krajangsri, Suppachai,Wu, Haibo,Liu, Jianguo,Rabten, Wangchuk,Singh, Thishana,Andersson, Pher G.
-
-
Read Online
- Chiral bidentate (phosphinophenyl)benzoxazine ligands in asymmetric catalysis
-
The new chiral bidentate (phosphinoaryl)benzoxazine ligands 2 were applied in asymmetric catalysis, Rhodium and copper complexes catalyzed the hydrosilylation of acetophenone and [4 + 2] cycloadditions with moderate enantioselectivity. Iridium complexes were used to hyrogenate di-, tri-, and tetrasubstituted alkenes, giving products with moderate to high enantiomer excesses. Enantioselective allylic substitution and Heck reactions catalyzed by [(phosphinoaryl)benzoxazine]palladium complexes occurred with high enantioselectivities. The results were similar to those obtained with the corresponding dihydro(phosphinoaryl)oxazole ligands. Comparison of the structures of (diphenylallyl)(benzoxazine)palladium and (diphenylallyl)(dihydrooxazole)-palladium complexes showed that the coordination geometries and the chiral environments of the metal centers are very similar, which explains why the enantioselectivities induced by the two ligand classes are in the same range.
- Bernardinelli, Gerald H.,Kuendig, E. Peter,Meier, Peter,Pfaltz, Andreas,Radkowski, Karin,Zimmermann, Nicole,Neuburger-Zehnder, Margareta
-
-
Read Online
- Catalytic asymmetric conjugate reduction of β,β-disubstituted α,β-unsaturated sulfones
-
(Chemical Equation Presented) Access to a chiral sulfone: Asymmetric conjugate reduction of β,β-disubstituted α,β-unsaturated 2-pyridylsulfones with silanes under CuI/binap catalysis provides chiral sulfones with excellent chemical yields and e
- Llamas, Tomas,Arrayas, Ramon Gomez,Carretero, Juan C.
-
-
Read Online
- NeoPHOX - A structurally tunable ligand system for asymmetric catalysis
-
A synthesis of new NeoPHOX ligands derived from serine or threonine has been developed. The central intermediate is a NeoPHOX derivative bearing a methoxycarbonyl group at the stereogenic center next to the oxazoline N atom. The addition of methylmagnesiu
- Padevět, Jaroslav,Schrems, Marcus G.,Scheil, Robin,Pfaltz, Andreas
-
-
Read Online
- Studies on the Enantiomers of RC-33 as Neuroprotective Agents: Isolation, Configurational Assignment, and Preliminary Biological Profile
-
In this study we addressed the role of chirality in the biological activity of RC-33, recently studied by us in its racemic form. An asymmetric synthesis procedure was the first experiment, leading to the desired enantioenriched RC-33 but with an enantiom
- Rossi, Daniela,Pedrali, Alice,Marra, Annamaria,Pignataro, Luca,Schepmann, Dirk,Wuensch, Bernhard,Ye, Lian,Leuner, Kristina,Peviani, Marco,Curti, Daniela,Azzolina, Ornella,Collina, Simona
-
-
Read Online
- Study of the recycling possibilities for azabis(oxazoline)-cobalt complexes as catalysts for enantioselective conjugate reduction
-
Azabis(oxazoline)-cobalt(ii) complexes have been tested in multiphasic catalytic systems for enantioselective conjugate reduction of (E)-3-phenylbut-2-enoate with NaBH4. Immobilization by electrostatic interactions with laponite clay leads to e
- Aldea, Luis,Fraile, Jose M.,Garcia-Marin, Hector,Garcia, Jose I.,Herrerias, Clara I.,Mayoral, Jose A.,Perez, Ignacio
-
-
Read Online
- Indene Derived Phosphorus-Thioether Ligands for the Ir-Catalyzed Asymmetric Hydrogenation of Olefins with Diverse Substitution Patterns and Different Functional Groups
-
A family of phosphite/phosphinite-thioether ligands have been tested in the Ir-catalyzed asymmetric hydrogenation of a range of olefins (50 substrates in total). The presented ligands are synthesized in three steps from cheap indene and they are air-stable solids. Their modular architecture has been crucial to maximize the catalytic performance for each type of substrate. Improving most Ir-catalysts reported so far, this ligand family presents a broader substrate scope, covering different substitution patterns with different functional groups, ranging from unfunctionalized olefins, through olefins with poorly coordinative groups, to olefins with coordinative functional groups. α,β-Unsaturated acyclic and cyclic esters, ketones and amides werehydrogenated in enantioselectivities ranging from 83 to 99% ee. Enantioselectivities ranging from 91 to 98% ee were also achieved for challenging substrates such as unfunctionalized 1,1′-disubstituted olefins, functionalized tri- and 1,1′-disubstituted vinyl phosphonates, and β-cyclic enamides. The catalytic performance of the Ir-ligand assemblies was maintained when the environmentally benign 1,2-propylene carbonate was used as solvent. (Figure presented.).
- Margalef, Jèssica,Biosca, Maria,de la Cruz-Sánchez, Pol,Caldentey, Xisco,Rodríguez-Escrich, Carles,Pàmies, Oscar,Pericàs, Miquel A.,Diéguez, Montserrat
-
-
Read Online
- Biaryl phosphite-oxazolines from hydroxyl aminoacid derivatives: Highly efficient modular ligands for Ir-catalyzed hydrogenation of alkenes
-
High enantioselectivities and activities are achieved in the Ir-catalyzed hydrogenation of several unfunctionalized olefins using modular biaryl phosphite-oxazoline ligands from hydroxyl aminoacid derivatives; the presence of a biaryl phosphite group is crucial to this success. The Royal Society of Chemistry.
- Dieguez, Montserrat,Mazuela, Javier,Pamies, Oscar,Verendel, J. Johan,Andersson, Pher G.
-
-
Read Online
- New application possibilities of Reformatzky reagent for synthesis of substituted acetic acid ethyl ester
-
When generated in dichloromethane, the Reformatzky reagent from ethyl bromoacetate can react with diphenylchloromethane, 1-bromoadamantane and 1-phenylethyl chlorides to form the corresponding α-substituted ethyl acetates in excellent to good yields. The mechanism of these Reformatzky reactions is interpreted in terms of a carbocation as intermediate which originates from the interaction of the alkyl halide with the organozinc bromide.
- Bott
-
-
Read Online
- Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
-
We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
- Topf, Christoph,Vielhaber, Thomas
-
-
- A Bifunctional Copper Catalyst Enables Ester Reduction with H2: Expanding the Reactivity Space of Nucleophilic Copper Hydrides
-
Employing a bifunctional catalyst based on a copper(I)/NHC complex and a guanidine organocatalyst, catalytic ester reductions to alcohols with H2 as terminal reducing agent are facilitated. The approach taken here enables the simultaneous activation of esters through hydrogen bonding and formation of nucleophilic copper(I) hydrides from H2, resulting in a catalytic hydride transfer to esters. The reduction step is further facilitated by a proton shuttle mediated by the guanidinium subunit. This bifunctional approach to ester reductions for the first time shifts the reactivity of generally considered "soft"copper(I) hydrides to previously unreactive "hard"ester electrophiles and paves the way for a replacement of stoichiometric reducing agents by a catalyst and H2.
- Kaicharla, Trinadh,Ngoc, Trung Tran,Teichert, Johannes F.,Tzaras, Dimitrios-Ioannis,Zimmermann, Birte M.
-
supporting information
p. 16865 - 16873
(2021/10/20)
-
- Visible-Light-Enhanced Cobalt-Catalyzed Hydrogenation: Switchable Catalysis Enabled by Divergence between Thermal and Photochemical Pathways
-
The catalytic hydrogenation activity of the readily prepared, coordinatively saturated cobalt(I) precatalyst, (R,R)-(iPrDuPhos)Co(CO)2H ((R,R)-iPrDuPhos = (+)-1,2-bis[(2R,5R)-2,5-diisopropylphospholano]benzene), is described. While efficient turnover was observed with a range of alkenes upon heating to 100 °C, the catalytic performance of the cobalt catalyst was markedly enhanced upon irradiation with blue light at 35 °C. This improved reactivity enabled hydrogenation of terminal, di-, and trisubstituted alkenes, alkynes, and carbonyl compounds. A combination of deuterium labeling studies, hydrogenation of alkenes containing radical clocks, and experiments probing relative rates supports a hydrogen atom transfer pathway under thermal conditions that is enabled by a relatively weak cobalt-hydrogen bond of 54 kcal/mol. In contrast, data for the photocatalytic reactions support light-induced dissociation of a carbonyl ligand followed by a coordination-insertion sequence where the product is released by combination of a cobalt alkyl intermediate with the starting hydride, (R,R)-(iPrDuPhos)Co(CO)2H. These results demonstrate the versatility of catalysis with Earth-abundant metals as pathways involving open-versus closed-shell intermediates can be switched by the energy source.
- Mendelsohn, Lauren N.,MacNeil, Connor S.,Tian, Lei,Park, Yoonsu,Scholes, Gregory D.,Chirik, Paul J.
-
p. 1351 - 1360
(2021/02/01)
-
- Synthesis and Asymmetric Alkene Hydrogenation Activity of C2-Symmetric Enantioenriched Pyridine Dicarbene Iron Dialkyl Complexes
-
Enantioenriched N-alkyl-imidazole-substituted pyridine dicarbene iron dialkyl complexes have been synthesized and characterized by 1H NMR and zero-field 57Fe M?ssbauer spectroscopies as well as single-crystal X-ray diffraction. In benzene-d6, reversible coordination of N2 was observed establishing an equilibrium between a five-coordinate, S = 1 iron dialkyl derivative and the corresponding six-coordinate, diamagnetic dinitrogen complex. A modest enantioselectivity of 45% enantiomeric excess (ee) was observed for the catalytic asymmetric hydrogenation of 1-isopropyl-1-phenyl ethylene at 4 atm of H2 using 10 mol % of an enantioenriched iron dialkyl precatalyst, (ACNC)Fe(CH2SiMe3)2 ((ACNC) = bis(alkylimidazol-2-ylidene)pyridine). Decreasing the H2 pressure to 1 atm increased the ee to 70%. Incubation experiments established that the reaction of the iron dialkyl precatalysts with H2 initiates a background reaction leading to the generation of a less selective catalyst; suppressing this pathway is crucial for obtaining high enantioselectivity. The attempted hydrogenation of methyl-2-acetamidoacrylate identified a deactivation pathway where N-H bond activation generated an iron alkyl κ2-amidate alkyl. For productive catalytic reactions, deuterium labeling studies are consistent with a pathway for hydrogenation involving fast, reversible [2,1]-alkene insertion and a slow, enantiodetermining [1,2]-insertion. Monitoring the catalytic alkene hydrogenation reaction by NMR spectroscopy supports a homogeneous active catalyst that also undergoes C-H activation of the ACNC ligand backbone as a competing reaction.
- Viereck, Peter,Rummelt, Stephan M.,Soja, Natalia A.,Pabst, Tyler P.,Chirik, Paul J.
-
supporting information
p. 1053 - 1061
(2021/05/07)
-
- Asymmetric Hydrogenation of ?-Aryl Alkylidene Malonate Esters: Installing an Ester Group Significantly Increases the Efficiency
-
Herein, we report a practical method for efficient asymmetric hydrogenation of β-aryl alkylidene malonates. With a site-specifically tailored chiral spiro iridium catalyst, a series of β-aryl alkylidene malonate esters were hydrogenated to afford chiral m
- Zhao, Qian-Kun,Wu, Xiong,Li, Lin-Ping,Yang, Fan,Xie, Jian-Hua,Zhou, Qi-Lin
-
supporting information
p. 1675 - 1680
(2021/03/08)
-
- Asymmetric Umpolung Hydrogenation and Deuteration of Alkenes Catalyzed by Nickel
-
Nickel-catalyzed asymmetric hydrogenation of several types of alkenes proceeds in high enantioselectivity, using acetic acid or water as the hydrogen source and indium powder as electron donor. The scope of alkenes herein include α,β-unsaturated esters, n
- Guo, Siyu,Wang, Xiuhua,Zhou, Jianrong Steve
-
supporting information
p. 1204 - 1207
(2020/02/04)
-
- Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands
-
A chiral phenol–NHC ligand enabled the copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters. The phenol moiety of the chiral NHC ligand played a critical role in producing the enantiomerically enriched products. The catalyst worked well for various (Z)-isomer substrates. Opposite enantiomers were obtained from (Z)- and (E)-isomers, with a higher enantiomeric excess from the (Z)-isomer.
- Mimura, Shohei,Mizushima, Sho,Sawamura, Masaya,Shimizu, Yohei
-
supporting information
p. 537 - 543
(2020/05/14)
-
- Diboron-Mediated Rhodium-Catalysed Transfer Hydrogenation of Alkenes and Carbonyls
-
A diboron-mediated rhodium-catalysed transfer hydrogenation system using water as the hydrogen donor is developed. In addition to a series of alkenes with good functional group tolerance, this rhodium-based catalytic system also effectively reduces aldehydes and ketones. A plausible mechanism involving the RhI-catalysed hydrogen generation and Rh0-catalysed hydrogenation is proposed for the reaction.
- Lin, Xiao,Wang, Yuhan,Hu, Yan,Zhu, Wanjiang,Dou, Xiaowei
-
supporting information
p. 1046 - 1049
(2020/02/25)
-
- Environmentally responsible, safe, and chemoselective catalytic hydrogenation of olefins: ppm level Pd catalysis in recyclable water at room temperature
-
Textbook catalytic hydrogenations are typically presented as reactions done in organic solvents and oftentimes under varying pressures of hydrogen using specialized equipment. Catalysts new and old are all used under similar conditions that no longer reflect the times. By definition, such reactions are both environmentally irresponsible and dangerous, especially at industrial scales. We now report on a general method for chemoselective and safe hydrogenation of olefins in water using ppm loadings of palladium from commercially available, inexpensive, and recyclable Pd/C, together with hydrogen gas utilized at 1 atmosphere. A variety of alkenes is amenable to reduction, including terminal, highly substituted internal, and variously conjugated arrays. In most cases, only 500 ppm of heterogeneous Pd/C is sufficient, enabled by micellar catalysis used in recyclable water at room temperature. Comparison with several newly introduced catalysts featuring base metals illustrates the superiority of chemistry in water.
- Gallou, Fabrice,Gao, Eugene S.,Lipshutz, Bruce H.,Takale, Balaram S.,Thakore, Ruchita R.
-
supporting information
p. 6055 - 6061
(2020/10/14)
-
- Method for selective reduction α, β - unsaturated carbonyl compound carbon-carbon double bond (by machine translation)
-
The invention discloses a method for selectively reducing carbon-carbon double bonds in α and β - unsaturated carbonyl compounds, which comprises the following steps of adding α, β - unsaturated carbonyl compounds shown in formula (I) in an electrolysis system and reducing α and β - unsaturated carbonyl compounds with carbonyl-conjugated carbon-carbon double bonds through an electrochemical cathodic reduction reaction. Compared with the reported method, the method disclosed by the invention does not use a metal catalyst and an external oxidant; and the reaction raw material and the electrolyte are low in price, nontoxic and tasteless, simple and convenient in post-treatment. (by machine translation)
- -
-
Paragraph 0083-0086
(2020/06/17)
-
- Tetrahydroquinoline skeleton chiral phosphine-nitrogen ligand and preparation method and application thereof
-
The invention relates to the field of asymmetric catalytic hydrogenation, in particular to a tetrahydroquinoline skeleton chiral phosphine-nitrogen ligand and a preparation method and application thereof. The tetrahydroquinoline skeleton chiral phosphine-
- -
-
Paragraph 0184-0189
(2020/11/10)
-
- Tertiary alkylations of aldehydes, ketones or imines using benzylic organoboronates and a base catalyst
-
The KHMDS-catalyzed tertiary alkylation of aldehydes, ketones or imines using tertiary benzylic organoboronates is reported. This protocol permitted the use of tertiary benzylic alkylboronates as the tertiary alkyl anion for construction of highly congested contiguous sp3 carbon centers. The mild and transition-metal-free reaction conditions are attractive features of the protocol.
- Nagao, Kazunori,Nakamura, Kei,Ohmiya, Hirohisa,Sato, Yukiya,Yabushita, Kenya
-
p. 1065 - 1069
(2020/11/09)
-
- Synthesis of Enantioenriched α,α-Difluoro-β-arylbutanoic Esters by Pd-Catalyzed Asymmetric Hydrogenation
-
Synthesis of optically active gem-difluorinated organic molecules attracts a great deal of interest due to their unique properties in pharmaceutical and agrochemical areas. Herein, a series of enantioenriched α,α-difluoro-β-arylbutanoic esters were prepar
- Dong, Kaiwu,Feng, Sitian,Shen, Chaoren,Tang, Yitian,Yang, Chenjue
-
p. 7508 - 7512
(2020/10/09)
-
- Enantioselective synthesis of tunable chiral pyridine-aminophosphine ligands and their applications in asymmetric hydrogenation
-
A small library of tunable chiral pyridine-aminophosphine ligands were enantioselectively synthesized based on chiral 2-(pyridin-2-yl)-substituted 1,2,3,4-tetrahydroquinoline scaffolds, which were obtained in high yields and with excellent enantioselectivities via ruthenium-catalyzed asymmetric hydrogenation of 2-(pyridin-2-yl)quinolines. The protocol features a wide substrate scope and mild reaction conditions, enabling scalable synthesis. These chiral P,N ligands were successfully applied in the Ir-catalyzed asymmetric hydrogenation of benchmark olefins and challenging seven-membered cyclic imines including benzazepines and benzodiazepines. Excellent enantio- and diastereoselectivity (up to 99% ee and >20:1 dr), and/or unprecedented chemoselectivity were obtained in the asymmetric hydrogenation of 2,4-diaryl-3H-benzo[b]azepines and 2,4-diaryl-3H-benzo[b][1,4]diazepines.
- Liu, Youran,Chen, Fei,He, Yan-Mei,Li, Chenghao,Fan, Qing-Hua
-
supporting information
p. 5099 - 5105
(2019/05/29)
-
- Catalytic hydrogenation of α,β-unsaturated carboxylic acid derivatives using copper(i)/N-heterocyclic carbene complexes
-
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.
-
supporting information
p. 2293 - 2296
(2019/02/27)
-
- Electrochemical Hydrogenation with Gaseous Ammonia
-
As a carbon-free and sustainable fuel, ammonia serves as high-energy-density hydrogen-storage material. It is important to develop new reactions able to utilize ammonia as a hydrogen source directly. Herein, we report an electrochemical hydrogenation of alkenes, alkynes, and ketones using ammonia as the hydrogen source and carbon electrodes. A variety of heterocycles and functional groups, including for example sulfide, benzyl, benzyl carbamate, and allyl carbamate were well tolerated. Fast stepwise electron transfer and proton transfer processes were proposed to account for the transformation.
- Li, Jin,He, Lingfeng,Liu, Xu,Cheng, Xu,Li, Guigen
-
supporting information
p. 1759 - 1763
(2019/01/16)
-
- Catalytic Hydrogenations with Cationic Heteroleptic Copper(I)/N-Heterocyclic Carbene Complexes
-
A new heteroleptic cationic copper(I) complex bearing two N-heterocyclic carbene (NHC) ligands has been prepared. In situ, a Cu-O bond can be generated which enables the complex to catalytically activate H 2. The resulting complex shows activit
- Thiel, Niklas O.,Brechmann, Lea T.,Teichert, Johannes F.
-
supporting information
p. 783 - 787
(2019/04/25)
-
- Identification of an Esterase Isolated Using Metagenomic Technology which Displays an Unusual Substrate Scope and its Characterisation as an Enantioselective Biocatalyst
-
Evaluation of an esterase annotated as 26D isolated from a marine metagenomic library is described. Esterase 26D was found to have a unique substrate scope, including synthetic transformations which could not be readily effected in a synthetically useful manner using commercially available enzymes. Esterase 26D was more selective towards substrates which had larger, more sterically demanding substituents (i. e. iso-propyl or tert-butyl groups) on the β-carbon, which is in contrast to previously tested commercially available enzymes which displayed a preference for substrates with sterically less demanding substituents (e.g. methyl group) at the β-carbon. (Figure presented.).
- Gavin, Declan P.,Murphy, Edel J.,Foley, Aoife M.,Castilla, Ignacio Abreu,Reen, F. Jerry,Woods, David F.,Collins, Stuart G.,O'Gara, Fergal,Maguire, Anita R.
-
p. 2466 - 2474
(2019/03/11)
-
- Giving a Second Chance to Ir/Sulfoximine-Based Catalysts for the Asymmetric Hydrogenation of Olefins Containing Poorly Coordinative Groups
-
This work identifies a family of Ir/phosphite-sulfoximine catalysts that has been successfully used in the asymmetric hydrogenation of olefins with poorly coordinative or noncoordinative groups. In comparison with analogue Ir/phosphine-sulfoximine catalysts previously reported, the presence of a phosphite group extended the range of olefins than can be efficiently hydrogenated. High enantioselectivities, comparable to the best ones reported, have been achieved for a wide range of olefins containing relevant poorly coordinative groups such as α,β-unsaturated enones, esters, lactones, and lactams as well as alkenylboronic esters.
- Biosca, Maria,Pàmies, Oscar,Diéguez, Montserrat
-
p. 8259 - 8266
(2019/06/17)
-
- Phosphite-thioether/selenoether Ligands from Carbohydrates: An Easily Accessible Ligand Library for the Asymmetric Hydrogenation of Functionalized and Unfunctionalized Olefins
-
A large family of phosphite-thioether/selenoether ligands has been easily prepared from accessible L-(+)-tartaric acid and D-(+)-mannitol and applied in the M-catalyzed (M=Ir, Rh) asymmetric hydrogenation of a broad number of substrates (46 in total). Its highly modular architecture has been crucial to maximize the catalytic performance. Improving most of the reported approaches, this ligand family presents a broad substrate scope. By selecting the ligand parameters high enantioselectivities (ee's up to 99 %) have therefore been achieved in a broad range of both, functionalized and unfunctionalized substrates. Interestingly, both enantiomers of the hydrogenation products can be usually achieved by changing the ligand parameters.
- Margalef, Jèssica,Borràs, Carlota,Alegre, Sabina,Alberico, Elisabetta,Pàmies, Oscar,Diéguez, Montserrat
-
p. 2142 - 2168
(2019/04/13)
-
- A chiral containing imine pyridine oxazoline compounds and its preparation method
-
The invention discloses a synthetic compound comprising iminopyridyl oxazoline, a preparation method thereof, a metal complex of the compound and application of a prochiral organic compound which contains at least one carbon/carbon or carbon/heteroatomic
- -
-
Paragraph 0138; 0142-0144
(2018/03/01)
-
- Pyrrolidine-Based P,O Ligands from Carbohydrates: Easily Accessible and Modular Ligands for the Ir-Catalyzed Asymmetric Hydrogenation of Minimally Functionalized Olefins
-
The potential of P,O-iminosugar based ligands in the Ir-catalyzed asymmetric hydrogenation of minimally functionalized olefins is presented. These new ligands were prepared from easily available carbohydrates (D-mannose, D-ribose and D-arabinose). The stereochemical and polyfunctional diversity of carbohydrates allowed the modulation of the ligands, both from their electronic properties and the rigidity of their backbone. High enantioselectivities (ee’s up to 99 %) can be reached in the hydrogenation of selected tri- and disubstituted substrates.
- Elías-Rodríguez, Pilar,Borràs, Carlota,Carmona, Ana T.,Faiges, Jorge,Robina, Inmaculada,Pàmies, Oscar,Diéguez, Montserrat
-
p. 5414 - 5424
(2018/12/11)
-
- ORGANIC REACTIONS CARRIED OUT IN AQUEOUS SOLUTION IN THE PRESENCE OF A HYDROXYALKYL(ALKYL)CELLULOSE OR AN ALKYLCELLULOSE
-
The present invention relates to a method of carrying out an organic reaction in aqueous solution in the presence of a hydroxyalkyl(alkyl)cellulose or an alkylcellulose.
- -
-
Page/Page column 253; 254
(2017/08/21)
-
- Copper(i)-catalysed transfer hydrogenations with ammonia borane
-
Highly Z-selective alkyne transfer semihydrogenations and conjugate transfer hydrogenations of enoates can be effected by employing a readily available and air-stable copper(i)/N-heterocyclic carbene (NHC) complex, [IPrCuOH]. As an easy to handle and potentially recyclable H2 source, ammonia borane (H3NBH3) is used.
- Korytiaková, Eva,Thiel, Niklas O.,Pape, Felix,Teichert, Johannes F.
-
supporting information
p. 732 - 735
(2017/01/13)
-
- Diazaphospholene Precatalysts for Imine and Conjugate Reductions
-
The first examples of 1,3,2-diazaphospholene-catalyzed imine reduction and conjugate reduction reactions are reported. This approach employs readily synthesized alkoxydiazaphospholene precatalysts that can be handled in open air. Reduction of substrates containing Lewis basic functionality, isolated unsaturation, and protic functional groups was accomplished. The synthetic utility of this approach is demonstrated by the synthesis of the important antiparkinson medicine rasagiline and the natural product zingerone.
- Adams, Matt R.,Tien, Chieh-Hung,Huchenski, Blake S. N.,Ferguson, Michael J.,Speed, Alexander W. H.
-
supporting information
p. 6268 - 6271
(2017/05/19)
-
- Palladium Nanoparticle Loaded Bifunctional Silica Hybrid Material: Preparation and Applications as Catalyst in Hydrogenation Reactions
-
Bifunctional mesoporous silica was prepared by co-condensation of tetraethyl orthosilicate (TEOS) with functionalized organosilanes containing azides or alkoxyamines. Orthogonal functional groups at the particles were selectively addressed in subsequent chemical modifications through “click”-chemistry (“click to ligand” strategy) and radical nitroxide exchange. Palladation with PdCl2 delivered Pd nanoparticle-loaded silica material bearing sulfoxides and additional aminoamides as stabilizing ligands by means of in situ reduction of the PdII-salt. These functional particles were successfully applied to the hydrogenation of alkynes and alkenes. Aldehyde hydrodeoxygenation and benzyl ether cleavage were achieved with these hybrid catalysts under mild conditions. Particles were analyzed by IR, TEM/STEM, EDX, and solid-state NMR spectroscopy.
- Surmiak, Sabrina K.,Doerenkamp, Carsten,Selter, Philipp,Peterlechner, Martin,Sch?fer, Andreas H.,Eckert, Hellmut,Studer, Armido
-
p. 6019 - 6028
(2017/05/05)
-
- Catalytic, Enantioselective β-Protonation through a Cooperative Activation Strategy
-
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.
-
p. 4689 - 4702
(2017/05/12)
-
- Alternatives to Phosphinooxazoline (t-BuPHOX) Ligands in the Metal-Catalyzed Hydrogenation of Minimally Functionalized Olefins and Cyclic β-Enamides
-
This study presents a new series of readily accessible iridium- and rhodium-phosphite/oxazoline catalytic systems that can efficiently hydrogenate, for the first time, both minimally functionalized olefins and functionalized olefins (62 examples in total) in high enantioselectivities (ees up to >99%) and conversions. The phosphite-oxazoline ligands, which are readily available in only two synthetic steps, are derived from previous privileged 4-alkyl-2-[2-(diphenylphosphino)phenyl]-2-oxazoline (PHOX) ligands by replacing the phosphine moiety by a biaryl phosphite group and/or the introduction of a methylene spacer between the oxazoline and the phenyl ring. The modular design of the ligands has given us the opportunity not only to overcome the limitations of the iridium-PHOX catalytic systems in the hydrogenation of minimally functionalized Z-olefins and 1,1-disubstituted olefins, but also to expand their use to unfunctionalized olefins containing other challenging scaffolds (e.g., exocyclic benzofused and triaryl-substituted olefins) and also to olefins with poorly coordinative groups (e.g., α,β-unsaturated lactams, lactones, alkenylboronic esters, etc.) with enantioselectivities typically >95% ee. Moreover, both enantiomers of the hydrogenation product could be obtained by simply changing the configuration of the biaryl phosphite moiety. Remarkably, the new catalytic systems also provided excellent enantioselectivities (up to 99% ee) in the asymmetric hydrogenation of another challenging class of olefins – the functionalized cyclic β-enamides. Again, both enantiomers of the reduced amides could be obtained by changing the metal from Ir to Rh. We also demonstrated that environmentally friendly propylene carbonate can be used with no loss of enantioselectivity. Another advantage of the new ligands over the PHOX ligands is that the best ligands are derived from the affordable (S)-phenylglycinol rather than from the expensive (S)-tert-leucinol. (Figure presented.).
- Biosca, Maria,Magre, Marc,Coll, Mercè,Pàmies, Oscar,Diéguez, Montserrat
-
supporting information
p. 2801 - 2814
(2017/08/23)
-
- N,N-Dimethylformamide as Hydride Source in Nickel-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Esters
-
Asymmetric transfer hydrogenation of α,β-unsaturated esters is realized by using a nickel/bisphosphine catalyst and N,N-dimethylformamide (DMF) as the hydride source.
- Guo, Siyu,Zhou, Jianrong
-
supporting information
p. 5344 - 5347
(2016/11/02)
-
- Preparation method of 5-(substituted benzimido)-4-substituted phenylisoxazole-3-carboxylic ethyl ester derivatives
-
The invention discloses a preparation method of 5-(substituted benzimido)-4-substituted phenylisoxazole-3-carboxylic ethyl ester derivatives with antibacterial activity. The 5-(substituted benzimido)-4-substituted phenylisoxazole-3-carboxylic ethyl ester derivatives include compounds and stereoisomers and medically applicable salts of the compounds, wherein a structural formula of the compounds is as shown in the specification. The invention further discloses the 5-(substituted benzimido)-4-substituted phenylisoxazole-3-carboxylic ethyl ester derivatives and medically applicable acid addition salts thereof, wherein the medically applicable acid addition salts can be used with existing medicines or used independently. According to in-vitro tests, the 5-(substituted benzimido)-4-substituted phenylisoxazole-3-carboxylic ethyl ester derivatives are high in antibacterial activity and antituberculous activity and have a promising prospect in preparation of antituberculous medicines.
- -
-
Paragraph 0039; 0040
(2016/10/10)
-
- Chiral ferrocene-based P,S ligands for Ir-catalyzed hydrogenation of minimally functionalized olefins. Scope and limitations
-
A family of 12 modular ferrocenyl planar chiral phosphine-thioethers (P,S) has been studied in the asymmetric hydrogenation of minimally functionalized alkenes. These ligands differ by the substituent on sulfur or by the linker between the ferrocene moiety and the sulfur atom (no linker, methylene or methyl substituted methylene linker bearing an additional element of chirality). The cationic iridium(cod) complexes of the different P,S ligands have been efficiently synthesized. For the majority of the ligands, coordination yielded only a single diastereoisomer with full control of the absolute configuration on sulfur. The different iridium complexes have been used in the hydrogenation of various di, tri, and tetrasubstituted minimally functionalized olefins. Conversions and enantioselectivities are highly dependent on the ligand and substrate structure. Full conversions and low-to-excellent enantioselectivities could be obtained (maximum ee from 14 to 94% for 1,1-disubsituted alkenes, from 17 to 99% for trisubstituted olefins, and 34% for the tetrasubstituted alkene).
- Biosca, Maria,Coll, Mercè,Lagarde, Florian,Brémond, Emma,Routaboul, Lucie,Manoury, Eric,Pàmies, Oscar,Poli, Rinaldo,Diéguez, Montserrat
-
p. 2623 - 2631
(2015/03/30)
-
- Synthesis of NHC-Oxazoline Pincer Complexes of Rh and Ru and Their Catalytic Activity for Hydrogenation and Conjugate Reduction
-
We describe the preparation and catalytic reactions of new CCN pincer Rh and Ru complexes containing NCH-oxazoline hybrid ligands. Oxazolinyl-phenyl-imidazolium derivatives (3) were suitable ligand precursors for the CCN pincer scaffold. C-H bond activation of 3 with RhCl3·3H2O in the presence of NEt3 yielded the desired CCN pincer Rh complexes 5 in 13-27% yields. The related CCN pincer Ru complexes 8-10 were synthesized in good yields by C-H bond activation of p-cymene Ru complexes 7 in the presence of NaOAc in DMF. The chiral complexes 8 and 9 had two diastereomers according to the coordination of CO and OAc ligands. The CCN Rh complexes showed catalytic activity for conjugate reduction of ethyl β-methylcinnamate with hydrosilane, with moderate enantioselectivity. The CCN Ru complexes were found to be active in the hydrogenation of aromatic ketones. In particular, hydrogenation of 9-acetylanthracene took place at not only the C=O bond but also the anthracene ring. The Ru complexes were also used as catalysts in the transfer hydrogenation of 9-acetylanthracene with 2-propanol; again, both the C=O bond and the anthracene ring were hydrogenated.
- Ito, Jun-Ichi,Sugino, Kanae,Matsushima, Satoru,Sakaguchi, Hiroki,Iwata, Hiroshi,Ishihara, Takahiro,Nishiyama, Hisao
-
p. 1885 - 1894
(2016/07/06)
-
- Ligand-free nickel-catalysed 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds
-
A simple and efficient ligand-free nickel-based catalytic system has been developed for the 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds. With catalyst loadings of 1-2 mol%, a series of 1,4-adducts from chalcones and cinnamates was obtained in moderate to excellent yields within 5-30 min under a nitrogen atmosphere and microwave irradiation. The 1,4-addition of arylboronic acids to acrylates is less efficient.
- Chen, Wen,Sun, Lu,Huang, Xi,Wang, Jiayi,Peng, Yanqing,Song, Gonghua
-
p. 1474 - 1482
(2015/05/19)
-
- Nickel-catalyzed asymmetric transfer hydrogenation of conjugated olefins
-
Asymmetric transfer hydrogenation of electron-deficient olefins is realized with nickel catalysts supported by strongly σ-donating bisphosphines. Deuterium labeling experiments point to a reaction sequence of formate decarboxylation, asymmetric hydride in
- Guo, Siyu,Yang, Peng,Zhou, Jianrong
-
supporting information
p. 12115 - 12117
(2015/07/28)
-
- Chiral Metal Nanoparticle Systems as Heterogeneous Catalysts beyond Homogeneous Metal Complex Catalysts for Asymmetric Addition of Arylboronic Acids to α,β-Unsaturated Carbonyl Compounds
-
We describe the use of chiral metal nanoparticle systems, as novel heterogeneous chiral catalysts for the asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds, as representative C-C bond-forming reactions. The reactions proceeded smoothly to afford the corresponding β-arylated products in high to excellent yields and outstanding enantioselectivities with wide substrate scope. Remarkably, the nanoparticle catalysts showed performance in terms of yield, enantioselectivity, and catalytic turnover that was superior to that of the corresponding homogeneous metal complexes. The catalyst can be successfully recovered and reused in a gram-scale synthesis with low catalyst loading without significant loss of activity. The nature of the active species was investigated, and we found that characteristic features of the nanoparticle system were totally different from those of the metal complex system. (Chemical Equation Presented).
- Yasukawa, Tomohiro,Suzuki, Aya,Miyamura, Hiroyuki,Nishino, Kohei,Kobayashi, Shu
-
supporting information
p. 6616 - 6623
(2015/06/08)
-
- Iridium-Catalyzed Asymmetric Hydrogenation with Simple Cyclohexane-Based P/S Ligands: In Situ HP-NMR and DFT Calculations for the Characterization of Reaction Intermediates
-
We report a reduced but structurally valuable phosphite/phosphinite-thioether ligand library for the Ir-hydrogenation of 40 minimally functionalized alkenes, including relevant examples with poorly coordinative groups. We found that enantiomeric excesses are mainly dependent on the substrate structure and on some ligand parameters (i.e., the type of thioether/phosphorus moieties and the configuration of the phosphite group), whereas the substituents of the biaryl phosphite moiety had little impact. By tuning the ligand parameters we were able to find highly selective catalysts for a range of substrates (ees up to 99%). These phosphite/phosphinite-thioether ligands have a simple backbone and thus yield simple NMR spectra that reduce signal overlap and facilitate the identification of relevant intermediates. Therefore, by combining HP-NMR spectroscopy and theoretical studies, we were also able to identify the catalytically competent Ir-dihydride alkene species, which made it possible to explain the enantioselectivity obtained.
- Borràs, Carlota,Biosca, Maria,Pàmies, Oscar,Diéguez, Montserrat
-
supporting information
p. 5321 - 5334
(2015/11/18)
-
- Stereospecific SN2@P reactions: Novel access to bulky P-stereogenic ligands
-
The stereospecific hydrolysis of bulky aminophosphine boranes is reported for the first time. The resulting phosphinous acid boranes, upon activation, undergo stereospecific nucleophilic substitution reaction at the phosphorous center with amine nucleophi
- Orgué, Sílvia,Flores-Gaspar, Areli,Biosca, Maria,Pàmies, Oscar,Diéguez, Montserrat,Riera, Antoni,Verdaguer, Xavier
-
supporting information
p. 17548 - 17551
(2015/12/08)
-
- Iridium catalysts with Chiral bicyclic pyridine-phosphane ligands for the asymmetric hydrogenation of olefins
-
New bicyclic pyridine-phosphane ligands were prepared, and their iridium complexes were evaluated in asymmetric hydrogenation of trisubstituted olefins with non-coordinating and weakly coordinating substituents. The iridium catalysts showed high reactivity and enantioselectivity for both types of olefins. New pyridine-derived N,P-chelated iridium catalysts were prepared and evaluated in the asymmetric hydrogenation of trisubstituted olefins. High conversions and enantioselectivities were obtained. Copyright
- Quan, Xu,Parihar, Vijay Singh,Bera, Milan,Andersson, Pher G.
-
p. 140 - 146
(2014/01/06)
-
- A theoretically-guided optimization of a new family of modular P,S-ligands for iridium-catalyzed hydrogenation of minimally functionalized olefins
-
A library of modular iridium complexes derived from thioether-phosphite/phosphinite ligands has been evaluated in the asymmetric iridium-catalyzed hydrogenation of minimally functionalized olefins. The modular ligand design has been shown to be crucial in finding highly selective catalysts for each substrate. A DFT study of the transition state responsible for the enantiocontrol in the Ir-catalyzed hydrogenation is also described and used for further optimization of the crucial stereodefining moieties. Excellent enantioselectivities (enantiomeric excess (ee) values up to 99%) have been obtained for a range of substrates, including E- and Z-trisubstituted and disubstituted olefins, α,β-unsaturated enones, tri- and disubstituted alkenylboronic esters, and olefins with trifluoromethyl substituents.
- Margalef, Jèssica,Caldentey, Xisco,Karlsson, Erik A.,Coll, Mercè,Mazuela, Javier,Pàmies, Oscar,Diéguez, Montserrat,Pericàs, Miquel A.
-
supporting information
p. 12201 - 12214
(2015/03/31)
-