- 2,2′-Bipyridine-α,α′-trifluoromethyl-diol ligand: Synthesis and application in the asymmetric Et2Zn alkylation of aldehydes
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A chiral 2,2′-bipyridine ligand (1) bearing α,α′-trifluoromethyl-alcohols at 6,6′-positions was designed in five steps affording either the R,R or S,S enantiomer with excellent stereoselectivities, i.e. 97% de, >99% ee and >99.5% de, >99.5% ee, respectively. The key step for reaching high levels of stereoselectivity was demonstrated to be the resolution of the α-CF3-alcohol using (S)-ibuprofen as the resolving agent. An initial application for the 2,2′-bipyridine-α,α′-CF3-diol ligand was highlighted in the ZnII-catalyzed asymmetric ethylation reaction of aromatic, heteroaromatic, and aliphatic aldehydes. Synergistic electron deficiency and steric hindrance properties of the newly developed ligand afforded the corresponding alcohols in good to excellent yields (up to 99%) and enantioselectivities (up to 95% ee). As observed from single crystal diffraction analysis, the complexation of the 2,2′-bipyridine-α,α′-CF3-diol ligand generates an unusual hexacoordinated ZnII.
- Lauzon, Samuel,Ollevier, Thierry
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supporting information
p. 11025 - 11028
(2021/11/03)
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- Copper-Catalyzed Enantioconvergent Cross-Coupling of Racemic Alkyl Bromides with Azole C(sp2)?H Bonds
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The development of enantioconvergent cross-coupling of racemic alkyl halides directly with heteroarene C(sp2)?H bonds has been impeded by the use of a base at elevated temperature that leads to racemization. We herein report a copper(I)/cinchona-alkaloid-derived N,N,P-ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2)?H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α-chiral alkylated azoles, such as 1,3,4-oxadiazoles, oxazoles, and benzo[d]oxazoles as well as 1,3,4-triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2)?H bond and the involvement of alkyl radical species under the reaction conditions.
- Chang, Xiao-Yong,Chen, Ji-Jun,Gu, Qiang-Shuai,Jiang, Sheng-Peng,Li, Zhong-Liang,Liu, Lin,Liu, Xiao-Dong,Liu, Xin-Yuan,Su, Xiao-Long,Wang, Fu-Li,Yang, Chang-Jiang,Ye, Liu
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supporting information
p. 380 - 384
(2020/10/30)
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- Half-sandwich rhodium complexes with phenylene-based SCS ligands: Synthesis, characterization and catalytic activities for transfer hydrogenation of ketones
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A series of half-sandwich rhodium complexes with tridentate phenylene-based bis(thione) (SCS) ligand have been synthesized and characterized. Both half-sandwich rhodium complexes and phenylene-based bis(thione) compounds were fully characterized by 1H and 13C NMR spectra, mass spectrometry and single-crystal X-ray diffraction method. The catalytic activities of half-sandwich rhodium complexes toward the transfer hydrogenation of ketones to their corresponding alcohols were explored using 2-propanol as hydrogen source and solvent. And the half-sandwich rhodium complexes exhibited high catalytic activity for transfer hydrogenation of ketones with a broad functional group tolerance.
- Jia, Wei-Guo,Gao, Li-Li,Zhi, Xue-Ting,Li, Xiao-Dong,Wang, Zhi-Bao,Sun, Ying
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- Pincerlike molybdenum complex and preparation method thereof, catalytic composition and application thereof, and alcohol preparation method
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The invention discloses a clamp-type molybdenum complex, a preparation method, a corresponding catalyst composition and application. The method comprises the steps: obtaining 9 molybdenum complexes with different structures through coordination reaction of 2-(substituent ethyl)-(5, 6, 7, 8-tetrahydroquinolyl) amine and a corresponding carbonyl molybdenum metal precursor; and catalyzing a ketone compound transfer hydrogenation reaction through a molybdenum complex to generate 40 alcohol compounds. The preparation method of the molybdenum complex is simple, high in yield and good in stability. For a transfer hydrogenation reaction of ketone, the molybdenum-based catalytic system has high catalytic activity and small molybdenum loading capacity, is used for production of aromatic and aliphatic alcohols, and has the advantages of simple method, small environmental pollution and high yield.
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Paragraph 0125-0130
(2021/08/11)
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- Linear β-amino alcohol catalyst anchored on functionalized magnetite nanoparticles for enantioselective addition of dialkylzinc to aromatic aldehydes
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A linear β-amino alcohol ligand, previously found to be a very efficient catalyst for enantioselective addition of dialkylzinc to aromatic aldehydes, has been anchored on differently functionalized superparamagnetic core-shell magnetite-silica nanoparticles (1a and 1b). Its catalytic activity in the addition of dialkylzinc to aldehydes has been evaluated, leading to promising results, especially in the case of 1b for which the recovery by simple magnetic decantation and reuse was successfully verified. This journal is
- Ciprioti, Stefano Vecchio,De Angelis, Martina,Di Pietro, Federica,Iannoni, Marika,Pilloni, Luciano,Primitivo, Ludovica,Ricelli, Alessandra,Righi, Francesco,Righi, Giuliana,Sappino, Carla,Suber, Lorenza
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p. 29688 - 29695
(2020/10/26)
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- Binaphthyl-based chiral ligands: Design, synthesis and evaluation of their performance in enantioselective addition of diethylzinc to aromatic aldehydes
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The design strategy and the performance of binaphthyl-based chiral ligands were evaluated with computation and enantioselective addition of diethylzinc to aromatic aldehydes. Under optimized conditions, enantioselective addition of diethylzinc to aromatic aldehydes provided the desired optically active secondary alcohols in high isolated yields (up to 91%) and excellent enantiomeric excesses (up to 98% ee).
- Yao, Chao,Wu, Piao,Huang, Yue,Chen, Yaoqi,Li, Lin,Li, Yue-Ming
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supporting information
p. 9712 - 9725
(2020/12/28)
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- Isosterically designed chiral catalysts: Rationale, optimization and their application in enantioselective nucleophilic addition to aldehydes
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Proline-based N,N′-dioxide ligands were designed on the basis of isosteric approach, and were successfully applied in enantioselective nucleophilic addition to aldehydes. In the presence of 10 mol% of chiral ligand 1b, enantioselective addition of diethylzinc to aldehydes provided the corresponding secondary alcohols in up to 90% isolated yield and up to 99% ee. Similarly, using 3e as chiral ligand, enantioselective arylation and alkynylation of aldehydes also proceeded readily, leading to the desired chiral alcohols in up to 92% isolated yield at 99% ee and 80% isolated yields and up to 84% ee, respectively. The current work would shed light on expanding the structure diversity in the design of chiral ligands and chiral catalysts.
- Gao, En,Li, Qiao,Duan, Lili,Li, Lin,Li, Yue-Ming
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supporting information
(2020/10/20)
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- Regiodivergent Hydroborative Ring Opening of Epoxides via Selective C-O Bond Activation
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A magnesium-catalyzed regiodivergent C-O bond cleavage protocol is presented. Readily available magnesium catalysts achieve the selective hydroboration of a wide range of epoxides and oxetanes yielding secondary and tertiary alcohols in excellent yields and regioselectivities. Experimental mechanistic investigations and DFT calculations provide insight into the unexpected regiodivergence and explain the different mechanisms of the C-O bond activation and product formation.
- Magre, Marc,Paffenholz, Eva,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 14286 - 14294
(2020/09/15)
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- Rhodium coordination compound as well as preparation method and application thereof
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The invention discloses a rhodium coordination compound as well as a preparation method and application thereof. The structure of the rhodium coordination compound is shown as a formula I which is described in the specification, wherein R is one of H and C1-C6 alkyl, and X is halogen. The rhodium coordination compound can efficiently catalyze a carbonyl transfer hydrogenation reaction to obtain corresponding alcohol, and meanwhile, the preparation method has the advantages of simple process and simplicity and convenience in operation.
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Paragraph 0133-0135
(2020/09/09)
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- Aza-crown compounds synthesised by the self-condensation of 2-amino-benzyl alcohol over a pincer ruthenium catalyst and applied in the transfer hydrogenation of ketones
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A well-defined PNN-Ru catalyst was revisited to self-condense 2-aminobenzyl alcohol in forming a series of novel aza-crown compounds [aza-12-crown-3 (1), aza-16-crown-4 (2) and aza-20-crown-5 (3)]. All aza-crown compounds are separated and determined by NMR, IR, and ESI-MS spectroscopy as well as X-ray crystallography, indicating the saddle structure of 1 and the twisted 1,3-alternate conformation structure of 3. These aza-crown compounds have been explored to study ferric initiation of transfer hydrogenation (TH) of ketones into their corresponding secondary alcohols in the presence of 2-propanol with a basic t-BuOK solution, achieving a high conversion (up to 95%) by a ferric complex with 2 in a low loading (0.05 mol%). This journal is
- Zhang, Shanshan,Wang, Zheng,Cao, Qianrong,Yue, Erlin,Liu, Qingbin,Ma, Yanping,Liang, Tongling,Sun, Wen-Hua
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supporting information
p. 15821 - 15827
(2020/11/24)
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- C1-Symmetric PNP Ligands for Manganese-Catalyzed Enantioselective Hydrogenation of Ketones: Reaction Scope and Enantioinduction Model
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A family of ferrocene-based chiral PNP ligands is reported. These tridentate ligands were successfully applied in Mn-catalyzed asymmetric hydrogenation of ketones, giving high enantioselectivities (92%~99% ee for aryl alkyl ketones) as well as high efficiencies (TON up to 2000). In addition, dialkyl ketones could also be hydrogenated smoothly. Manganese intermediates that might be involved in the catalytic cycle were analyzed. DFT calculation was carried out to help understand the chiral induction model. The Mn/PNP catalyst could discriminate two groups with different steric properties by deformation of the phosphine moiety in the flexible 5-membered ring.
- Zeng, Liyao,Yang, Huaxin,Zhao, Menglong,Wen, Jialin,Tucker, James H. R.,Zhang, Xumu
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p. 13794 - 13799
(2020/11/30)
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- Chiral P,N-ligands for the highly enantioselective addition of diethylzinc to aromatic aldehydes
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A new sterically hindered chiral P,N-ligand was synthesized and successfully applied to copper catalyzed asymmetric addition of diethylzinc to aromatic aldehydes. Various aromatic aldehydes can react smoothly to give the corresponding addition products with good to excellent enantioselectivities, which provides a readily accessible method for the preparation of chiral secondary alcohols.
- Wang, Qiang,Li, Shuang,Hou, Chuan-Jin,Chu, Ting-Ting,Hu, Xiang-Ping
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- Enantioselective addition of diethylzinc to aldehydes catalyzed by 5-cis-substituted proline derivatives
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5-Cis-substituted prolinols, prolinamines, and prolinamine sulfonamides proved to be efficient ligands for the enantioselective addition of diethylzinc to aldehydes, providing up to 99% ee. The sense of asymmetric induction can be controlled by the nature
- Prause, Felix,Wagner, Stefan,Breuning, Matthias
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- Cooperative Mn(i)-complex catalyzed transfer hydrogenation of ketones and imines
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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.
- Ganguli, Kasturi,Shee, Sujan,Panja, Dibyajyoti,Kundu, Sabuj
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p. 7358 - 7366
(2019/06/06)
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- Ruthenium(II)-Catalyzed β-Methylation of Alcohols using Methanol as C1 Source
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Selective introduction of methyl branches into the carbon chains of alcohols can be achieved with low loadings of ruthenium precatalyst [RuH(CO)(BH4)(HN(C2H4PPh2)2)] (Ru-MACHO-BH) using methanol both as methylating reagent and as reaction medium. A wide range of structurally divers alcohols was β-methylated with excellent selectivity (>99 %) in fair to high yields (up to 94 %) under standard conditions, and turnover numbers up to 18,000 could be established. The overall reaction rate of the complex catalytic network appears to be governed by interconnection of the individual subcycles through availability of the reactive intermediates. The synthetic procedure opens pathways to important structural motifs following the Green Chemistry principles.
- Kaithal, Akash,Schmitz, Marc,H?lscher, Markus,Leitner, Walter
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p. 5287 - 5291
(2019/05/28)
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- NBS-mediated synthesis of β-keto sulfones from benzyl alcohols and sodium arenesulfinates
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An efficient synthetic route towards the synthesis of β-keto sulfones has been developed from secondary benzyl alcohols using N-bromosuccinimide (NBS). The present protocol utilizes NBS as oxidant as well as brominating agent, readily accessible benzyl alcohols and sodium arenesulfinates as the sulfonylating reagent under mild conditions. The control experiments revealed that the reaction proceeds via oxidation of alcohol to ketone, α-bromination of ketone and nucleophilic substitution by sodium arenesulfinate. Furthermore, the efficiency of the methodology was tested with a gram scale reaction and also shown the synthetic utility.
- Muneeswara, Madithedu,Sundaravelu, Nallappan,Sekar, Govindasamy
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supporting information
p. 3479 - 3484
(2019/05/21)
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- Central-to-Helical-to-Axial-to-Central Transfer of Chirality with a Photoresponsive Catalyst
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Recent advances in molecular design have displayed striking examples of dynamic chirality transfer between various elements of chirality, e.g., from central to either helical or axial chirality and vice versa. While considerable progress in atroposelective synthesis has been made, it is intriguing to design chiral molecular switches able to provide selective and dynamic control of axial chirality with an external stimulus to modulate stereochemical functions. Here, we report the synthesis and characterization of a photoresponsive bis(2-phenol)-substituted molecular switch 1. The unique design exhibits a dynamic hybrid central-helical-axial transfer of chirality. The change of preferential axial chirality in the biaryl motif is coupled to the reversible switching of helicity of the overcrowded alkene core, dictated by the fixed stereogenic center. The potential for dynamic control of axial chirality was demonstrated by using (R)-1 as switchable catalyst to direct the stereochemical outcome of the catalytic enantioselective addition of diethylzinc to aromatic aldehydes, with successful reversal of enantioselectivity for several substrates.
- Pizzolato, Stefano F.,?tacko, Peter,Kistemaker, Jos C. M.,Van Leeuwen, Thomas,Otten, Edwin,Feringa, Ben L.
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supporting information
p. 17278 - 17289
(2019/01/04)
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- New chiral amino alcohol ligands for catalytic enantioselective addition of diethylzincs to aldehydes
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A study aimed at the synthesis and structure optimization of new, efficient, optically active β-amino alcohol ligands with a structure suitable for immobilization on magnetite nanoparticles has been carried out. The optimized homogeneous amino alcohol catalysts 13a and 13b, the chirality of which arises from the Sharpless epoxidation of suitable allyl alcohols, were tested by employing the well-established enantioselective amino alcohol-promoted addition of diethylzinc to benzaldehyde, giving the corresponding benzyl alcohol with nearly quantitative yield and ee = 95%. Then, their broad applicability as chiral catalysts was evaluated by carrying out the same reaction on a family of aldehydes, including variously substituted aromatic ones as well as an aliphatic analogue. The results have confirmed the validity of the fine-tuning process performed on ligands 13a and 13b. In fact, both exhibited excellent catalytic activity as demonstrated by the chemical yields and ee obtained from all the tested aldehydes, almost independent of the position and type of substitution in the aromatic ring.
- Sappino, Carla,Mari, Alessandra,Mantineo, Agnese,Moliterno, Mauro,Palagri, Matteo,Tatangelo, Chiara,Suber, Lorenza,Bovicelli, Paolo,Ricelli, Alessandra,Righi, Giuliana
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p. 1860 - 1870
(2018/03/23)
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- Programming cascade reactions interfacing biocatalysis with transition-metal catalysis in: Deep Eutectic Solvents as biorenewable reaction media
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The first application of Deep Eutectic Solvents (DESs) in the asymmetric bioreduction of ketones has been accomplished for purified ketoreductases (KREDs). The performance of the biocatalysts was enhanced by increasing the percentage of neoteric solvent in DES-buffer mixtures. At a buffer content of 50% (w/w) and even 20% (w/w), the combination of either choline chloride (ChCl)/glycerol (Gly) (1:2) or ChCl/sorbitol (1:1) proved to be most effective for achieving up to >99% conversion and up to >99% enantiomeric excess of the corresponding secondary alcohols. Moreover, this reaction medium was used to perform the first example of a chemoenzymatic cascade process in DES-buffer mixtures, namely the ruthenium-catalysed isomerisation of racemic allylic alcohols coupled with a further enantioselective bioreduction, in both sequential and concurrent modes.
- Cicco, Luciana,Ríos-Lombardía, Nicolás,Rodríguez-álvarez, María J.,Morís, Francisco,Perna, Filippo M.,Capriati, Vito,García-álvarez, Joaquín,González-Sabín, Javier
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p. 3468 - 3475
(2018/08/07)
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- Noscapine Derivatives as New Chiral Catalysts in Asymmetric Synthesis: Highly Enantioselective Addition of Diethylzinc to Aldehydes
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Noscapine, a natural alkaloid, has never been used as a parent scaffold in chiral induction. The first examples of noscapinoid compounds as efficient catalysts in asymmetric synthesis are now reported. Three derivatives of noscapine were synthesized from its reaction with different Grignard reagents. Asymmetric addition of diethylzinc to aldehydes was performed in the presence of these catalysts in high yields and good to excellentees.
- Mohebbi, Maryam,Bararjanian, Morteza,Ebrahimi, Samad N.,Smie?ko, Martin,Salehi, Peyman
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p. 1841 - 1848
(2018/02/14)
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- An air and moisture tolerant iminotrihydroquinoline-ruthenium(ii) catalyst for the transfer hydrogenation of ketones
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Reaction of 8-amino-5,6,7,8-tetrahydroquinoline with RuCl2(PPh3)3 at room temperature affords the ruthenium(ii) chelate (8-NH2-C9H10N)RuCl2(PPh3)2 (E), in which the two triphenylphosphine ligands are disposed mutually cis. By contrast, when the reaction is performed at reflux ligand oxidation/dehydrogenation occurs along with cis-trans reorganization of the triphenylphosphines to form the 8-imino-5,6,7-trihydroquinoline-ruthenium(ii) complex, (8-NH-C9H9N)RuCl2(PPh3)2 (F). Complex F can also be obtained in higher yield by heating a solution of E alone to reflux. Comparison of their molecular structures highlights the superior binding properties of the bidentate imine ligand in F over its amine-containing counterpart in E. Both complexes are highly effective in the transfer hydrogenation of a wide range of alkyl-, aryl- and cycloalkyl-containing ketones affording their corresponding secondary alcohols with loadings of as low as 0.1 mol%. Significantly, F can deliver excellent conversions even in bench quality 2-propanol in reaction vessels open to the air, whereas the catalytic efficiency of E is diminished by the presence of air but only operates efficiently under inert conditions.
- Li, Jiaoyan,Ma, Yingmiao,Wang, Zheng,Liu, Qingbin,Solan, Gregory A.,Ma, Yanping,Sun, Wen-Hua
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p. 8738 - 8745
(2018/07/13)
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- Nickel-Catalyzed Enantioconvergent Borylation of Racemic Secondary Benzylic Electrophiles
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Nickel-catalyzed cross-coupling has emerged as the most versatile approach to date for achieving enantioconvergent carbon–carbon bond formation using racemic alkyl halides as electrophiles. In contrast, there have not yet been reports of the application of chiral nickel catalysts to the corresponding reactions with heteroatom nucleophiles to produce carbon–heteroatom bonds with good enantioselectivity. Herein, we establish that a chiral nickel/pybox catalyst can borylate racemic secondary benzylic chlorides to provide enantioenriched benzylic boronic esters, a highly useful family of compounds in organic synthesis. The method displays good functional group compatibility (e.g., being unimpeded by the presence of an indole, a ketone, a tertiary amine, or an unactivated alkyl bromide), and both of the catalyst components (NiCl2?glyme and the pybox ligand) are commercially available.
- Wang, Zhaobin,Bachman, Shoshana,Dudnik, Alexander S.,Fu, Gregory C.
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supporting information
p. 14529 - 14532
(2018/09/14)
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- A Ferrocene-Based NH-Free Phosphine-Oxazoline Ligand for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones
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A new type of ferrocene-based phosphine-oxazoline ligand has been prepared over a few simple steps. An iridium complex of this ligand is air stable and exhibits excellent performance for the asymmetric hydrogenation of simple ketones (up to 98% yield, up to 99% ee, and 20?000 S/C). Exo-α,β-unsaturated cyclic ketones could be regiospecifically hydrogenated to give chiral allylic alcohols with good results. This study indicates that P,N-ligands can also efficiently promote Ir-catalyzed asymmetric hydrogenation without NH-hydrogen-bonding assistance.
- Wang, Yanzhao,Yang, Guoqiang,Xie, Fang,Zhang, Wanbin
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supporting information
p. 6135 - 6139
(2018/09/27)
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- Highly enantioselective asymmetric reactions involving zinc ions promoted by chiral aziridine alcohols
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Enantiomerically pure, chiral secondary and tertiary aziridine alcohols (including the aziridine analogue of ProPhenol—AziPhenol) have proven to be highly effective catalysts for enantioselective asymmetric reactions in the presence of zinc ions, including arylation of aromatic aldehydes, epoxidation of chalcone and addition of diethylzinc to aldehydes, leading to the desired chiral products in high chemical yields (up to 90%) and with ee's up to 90%. A higher catalytic activity of Prophenol-type bis(aziridine alcohol) in the aforementioned asymmetric transformations has been demonstrated.
- Jarzyński, Szymon,Utecht, Greta,Le?niak, Stanis?aw,Rachwalski, Micha?
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p. 1774 - 1779
(2017/11/16)
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- Novel chiral multidentate P3N4-type ligand for asymmetric transfer hydrogenation of aromatic ketones
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Novel chiral multidentate P3N4-type ligand has been synthesized and characterized by NMR and HRMS. Using i-PrOH as solvent and hydrogen source, asymmetric transfer hydrogenation of various ketones was investigated. The catalyst generated in situ from chiral multidentate aminophosphine ligand (R,R,R,R)-3 and IrCl(CO)(PPh3)2exhibited highly catalytic activity and excellent enantioselectivity under mild conditions, achieving the corresponding chiral alcohols with up to 99% yield and 99% ee.
- Tao, Meng,Wu, Fang,Li, Teng,Li, Yan-Yun,Gao, Jing-Xing
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- Asymmetric Reduction of Prochiral Ketones by Using Self-Sufficient Heterogeneous Biocatalysts Based on NADPH-Dependent Ketoreductases
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The development of cell-free and self-sufficient biocatalytic systems represents an emerging approach to address more complex synthetic schemes under nonphysiological conditions. Herein, we report the development of a self-sufficient heterogeneous biocatalyst for the synthesis of chiral alcohols without the need to add an exogenous cofactor. In this work, an NADPH-dependent ketoreductase was primarily stabilized and further co-immobilized with NADPH to catalyze asymmetric reductions without the addition of an exogenous cofactor. As a result, the immobilized cofactor is accessible, and thus, it is recycled inside the porous structure without diffusing out into the bulk, as demonstrated by single-particle in operando studies. This self-sufficient heterogeneous biocatalyst was used and recycled for the asymmetric reduction of eleven carbonyl compounds in a batch reactor without the addition of exogenous NADPH to achieve the corresponding alcohols in 100 % yield and >99 % ee; this high performance was maintained over five consecutive reaction cycles. Likewise, the self-sufficient heterogeneous biocatalyst was integrated into a plug flow reactor for the continuous synthesis of one model secondary alcohol, which gave rise to a space-time yield of 97–112 g L?1 day?1; additionally, the immobilized cofactor accumulated a total turnover number of 1076 for 120 h. This is one of the few examples of the successful implementation of continuous reactions in aqueous media catalyzed by cell-free and immobilized systems that integrate both enzymes and cofactors into the solid phase.
- Benítez-Mateos, Ana I.,San Sebastian, Eneko,Ríos-Lombardía, Nicolás,Morís, Francisco,González-Sabín, Javier,López-Gallego, Fernando
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p. 16843 - 16852
(2017/11/16)
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- Halogen-bonded iodonium ion catalysis: A route to α-hydroxy ketones: Via domino oxidations of secondary alcohols and aliphatic C-H bonds with high selectivity and control
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A domino synthesis of α-hydroxy ketones has been developed from benzylic secondary alcohols employing catalytic iodonium ions stabilized by DMSO. The reaction proceeds through an unprecedented sequential oxidation of alcohols to ketone and its α-hydroxylation in a controlled manner. The spectroscopic evidence establishes the possibility of formation of a stable halogen-bonded adduct between DMSO and iodonium ions.
- Guha, Somraj,Kazi, Imran,Mukherjee, Pranamita,Sekar, Govindasamy
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supporting information
p. 10942 - 10945
(2017/10/13)
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- Development of Axially Chiral Cyclo-Biaryldiol Ligands with Adjustable Dihedral Angles
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A new type of axially chiral cyclo-[1,1′-biphenyl]-2,2′-diol (CYCNOL) ligands with adjustable dihedral angles have been developed by varying the bridge chain length. Eight-, nine- and ten-membered cyclo-ligands were prepared and evaluated by using two representative examples: enantioselective additions of diethylzinc to aldehydes and organometallic reagents to enones. The results revealed that the fine regulation of dihedral angles through variation of the bridge chain length was effective in the asymmetric synthesis.
- Zhang, Pengxiang,Yu, Jipan,Peng, Fei,Wu, Xudong,Jie, Jiyang,Liu, Can,Tian, Hua,Yang, Haijun,Fu, Hua
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supporting information
p. 17477 - 17484
(2016/11/23)
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- Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by Chiral O,N,O-tridentate Phenol Ligands Derived from Camphor
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Chiral O,N,O-tridentate phenol ligands bearing a camphor backbone were found to be effective chiral catalysts for the enantioselective addition of diethylzinc to aromatic aldehydes, resulting in high enantioselectivities (80-95% ee) at room temperature.
- Lee, Dong-Sheng,Chang, Shu-Ming,Ho, Chun-Ying,Lu, Ta-Jung
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- Mechanistic implications of the enantioselective addition of alkylzinc reagents to aldehydes catalyzed by nickel complexes with α-amino amide ligands
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The enantioselective alkylation of aldehydes catalysed by nickel(ii)-complexes derived from α-amino amides was studied by means of density functional theory (DFT) and ONIOM (B3LYP:UFF) calculations. A mechanism was proposed in order to investigate the origin of enantioselectivity. The chirality-determining step for the alkylation was the formation of the intermediate complexes with the involvement of a 5/4/4-fused tricyclic transition state. The predominant products predicted theoretically were of (S)-configuration, in good agreement with experimental observations. The scope of the reaction was examined and high yields and enantioselectivities were observed for the enantioselective addition of Et2Zn and Me2Zn to aromatic and aliphatic aldehydes.
- Escorihuela, Jorge,Burguete, M. Isabel,Ujaque, Gregori,Lledós, Agustí,Luis, Santiago V.
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p. 11125 - 11136
(2016/12/07)
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- Homochiral 2D Porous Covalent Organic Frameworks for Heterogeneous Asymmetric Catalysis
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There have been breakthroughs in the development of covalent organic frameworks (COFs) with tunability of composition, structure, and function, but the synthesis of chiral COFs remains a great challenge. Here we report the construction of two-dimensional
- Wang, Xiuren,Han, Xing,Zhang, Jie,Wu, Xiaowei,Liu, Yan,Cui, Yong
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supporting information
p. 12332 - 12335
(2016/10/07)
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- Third-Generation Amino Acid Furanoside-Based Ligands from d-Mannose for the Asymmetric Transfer Hydrogenation of Ketones: Catalysts with an Exceptionally Wide Substrate Scope
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A modular ligand library of α-amino acid hydroxyamides and thioamides was prepared from 10 different N-tert-butyloxycarbonyl-protected α-amino acids and three different amino alcohols derived from 2,3-O-isopropylidene-α-d-mannofuranoside. The ligand library was evaluated in the half-sandwich ruthenium- and rhodium-catalyzed asymmetric transfer hydrogenation of a wide array of ketone substrates, including simple as well as sterically demanding aryl alkyl ketones, aryl fluoroalkyl ketones, heteroaromatic alkyl ketones, aliphatic, conjugated and propargylic ketones. Under the optimized reaction conditions, secondary alcohols were obtained in high yields and in enantioselectivities up to >99%. The choice of ligand/catalyst allowed for the generation of both enantiomers of the secondary alcohols, where the ruthenium-hydroxyamide and the rhodium-thioamide catalysts act complementarily towards each other. The catalytic systems were also evaluated in the tandem isomerization/asymmetric transfer hydrogenation of racemic allylic alcohols to yield enantiomerically enriched saturated secondary alcohols in up to 98% ee. Furthermore, the catalytic tandem α-alkylation/asymmetric transfer hydrogenation of acetophenones and 3-acetylpyridine with primary alcohols as alkylating and reducing agents was studied. Secondary alcohols containing an elongated alkyl chain were obtained in up to 92% ee. (Figure presented.).
- Margalef, Jèssica,Slagbrand, Tove,Tinnis, Fredrik,Adolfsson, Hans,Diéguez, Montserrat,Pàmies, Oscar
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p. 4006 - 4018
(2016/12/30)
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- From a Sequential to a Concurrent Reaction in Aqueous Medium: Ruthenium-Catalyzed Allylic Alcohol Isomerization and Asymmetric Bioreduction
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The ruthenium-catalyzed redox isomerization of allylic alcohols was successfully coupled with the enantioselective enzymatic ketone reduction (mediated by KREDs) in a concurrent process in aqueous medium. The overall transformation, formally the asymmetric reduction of allylic alcohols, took place with excellent conversions and enantioselectivities, under mild reaction conditions, employing commercially and readily available catalytic systems, and without external coenzymes or cofactors. Optimization resulted in a multistep approach and a genuine cascade reaction where the metal catalyst and biocatalyst coexist from the beginning.
- Ríos-Lombardía, Nicolás,Vidal, Cristian,Liardo, Elisa,Morís, Francisco,García-álvarez, Joaquín,González-Sabín, Javier
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p. 8691 - 8695
(2016/07/21)
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- Enantioselective addition of organozinc reagents to carbonyl compounds catalyzed by a camphor derived chiral γ-amino thiol ligand
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In this article, the design and synthesis of the chiral camphor derived γ-amino thiol ligand 17 and its application in catalytic enantioselective carbon-carbon forming reactions through the addition of organozinc reagents to carbonyl compounds is described. The catalytic activity and enantioselectivity of ligand 17 is demonstrated in the enantioselective addition of various organozinc reagents to aldehydes and ketoesters, offering the corresponding alcohols in high yields and enantioselectivities. The role of the mercapto group in the highly enantioselective 1,2-addition reaction of organozincs to aldehyde is also discussed.
- Wu, Hsyueh-Liang,Wu, Ping-Yu,Cheng, Ying-Ni,Uang, Biing-Jiun
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p. 2656 - 2665
(2016/05/10)
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- D-Penicillamine and L-cysteine derived thiazolidine catalysts: an efficient approach to both enantiomers of secondary alcohols
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D-Penicillamine derived thiazolidine ligands were prepared in a two-step synthetic sequence and used in the enantioselective alkylation of a variety of aromatic aldehydes with diethylzinc at room temperature. Excellent ee, up to >99%, and nearly complete conversions were observed. Structurally analogous L-cysteine derived thiazolidine ligands were also synthesized and tested for comparative purposes, resulting in very good, albeit slightly lower selectivities, up to 89%. The combined use of these two types of thiazolidines constitutes a very interesting strategy for synthesizing both (S) and (R) enantiomers of chiral secondary alcohols, thus leading the way to a myriad of useful optically active products with opposite absolute configurations.
- Serra, M. Elisa Silva,Costa, Dora,Murtinho, Dina,Tavares, Nélia C.T.,Pinho e Melo, Teresa M.V.D.
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p. 5923 - 5927
(2016/09/07)
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- Optimum bifunctionality in a 2-(2-pyridyl-2-ol)-1,10-phenanthroline based ruthenium complex for transfer hydrogenation of ketones and nitriles: Impact of the number of 2-hydroxypyridine fragments
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Considerable differences in reactivity and selectivity for 2-hydroxypyridine (2-HP) derived ruthenium complexes in transfer hydrogenation are described. Bifunctional Ru(ii)-(phenpy-OH) [phenpy-OH: 2-(2-pyridyl-2-ol)-1,10-phenanthroline] complex (2) exhibited excellent catalytic activity in transfer hydrogenation (TH) of ketones and nitriles. Notably, in comparison with all the reported 2-hydroxypyridine (2-HP) derived ruthenium complexes in transfer hydrogenation, complex 2 displayed significantly higher activity. Additionally, exploiting the metal-ligand cooperativity in complex 2, chemoselective TH of ketones was achieved and sterically demanding ketones were readily reduced. An outer-sphere mechanism is proposed for this system as exogenous PPh3 has no significant effect on the rate of this reaction. This is a rare example of a highly active bifunctional Ru(ii) catalyst bearing only one 2-HP unit.
- Paul, Bhaskar,Chakrabarti, Kaushik,Kundu, Sabuj
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supporting information
p. 11162 - 11171
(2016/07/16)
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- Phosphine-free chiral iridium catalysts for asymmetric catalytic hydrogenation of simple ketones
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Novel pyridylalkylamine and aminopyridinato ligand stabilized iridium complexes with no P ligand are introduced. These complexes have been investigated as catalysts for asymmetric hydrogenation of simple ketones, resulting in an active catalyst for bulky alkyl aryl ketones that is α-methylpropiophenone. The ligands were synthesized from inexpensive starting materials and their modular design allows for the introduction of a broad variety of substitution patterns. Additionally, better activity and selectivity was observed at 20 °C and 20 bar H2 pressure with a catalyst loading as low as 0.05 mol% iridium. These phosphorus free catalysts have always been a central issue in both academic and industrial research.
- Kumar, Prashant,Irrgang, Torsten,Kostakis, George E.,Kempe, Rhett
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p. 39335 - 39342
(2016/05/24)
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- Synthesis of dendrimer-supported ferrocenylmethyl aziridino alcohol ligands and their application in asymmetric catalysis
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A series of N-ferrocenylmethyl aziridino alcohol ligands bearing Frchet-type dendrimers were synthesized and applied in the asymmetric addition of diethylzinc to aldehydes affording chiral alcohols in excellent yields (up to 99%) and excellent enantiosele
- Zhao, Wen-Xian,Liu, Nian,Li, Gao-Wei,Chen, Dong-Li,Zhang, An-An,Wang, Min-Can,Liu, Lantao
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supporting information
p. 2924 - 2930
(2015/05/27)
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- Enantioselective addition of diethylzinc to aldehydes catalyzed by aziridine carbinols
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Abstract A series of enantiopure aziridine carbinols were synthesized from commercially available starting materials (l-serine and piperonylaldehyde), and characterized by 1H NMR, 13C NMR, HRMS, and IR. Their enantioselective induction behaviors were evaluated as chiral ligands in the asymmetric addition of diethylzinc and phenylethynylzinc to aryl and α,β-unsaturated aldehydes. Chiral aziridine carbinol 1h was found to catalyze the asymmetric addition of diethylzinc to aldehydes at low catalyst loadings (as little as 1 mol %), and the conversion rates were close to quantitative (up to 97% yield) with good to excellent enantiomeric excesses (up to 98% ee). A possible catalytic reaction mechanism is proposed.
- Wang, Xiaojuan,Zhao, Wenxian,Li, Gaowei,Liu, Guanjun,Wang, Jin,Wang, Mincan,Liu, Lantao
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p. 815 - 820
(2015/08/18)
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- Novel tridentate ligands derived from (+)-camphoric acid for enantioselective ethylation of aromatic aldehydes
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Novel tridentate ligands were prepared from (+)-camphoric acid, using simple synthetic sequences. The synthesized ligands were used in enantioselective ethylations of benzaldehydes, showing enantioselectivities up to 92%, at room temperature. Extending th
- Murtinho, Dina,Ogihara, Camila H.,Serra, M. Elisa Silva
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p. 1256 - 1260
(2015/11/16)
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- Asymmetric transfer hydrogenation of secondary allylic alcohols
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Racemic secondary allylic alcohols were transformed into optically active secondary alcohols by a combined Rucatalyzed isomerization/asymmetric transfer-hydrogenation reaction. The catalyst was generated in situ in isopropyl alcohol from di-μ-chlorobis[(p-cymene)chlororuthenium(II)], the chiral ligand (1S,2S)-N-(p-tolylsulfonyl)-1,2-diphenylethylenediamine, and K2CO3, and the products were afforded in yields up to 97% with up to 93% enantiomeric excess without the use of hydrogen gas. A Hammett study revealed that the reaction rate was enhanced with electronwithdrawing aryl substituents. The reaction supports the recent work published by Adolfsson et al. as new methodology for the synthesis of chiral compounds from allylic alcohols.
- Shoola, Christopher O.,DelMastro, Thomas,Wu, Ruoqiu,Sowa, John R.
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p. 1670 - 1673
(2015/05/27)
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- DMF Dimethyl Acetal as Carbon Source for α-Methylation of Ketones: A Hydrogenation-Hydrogenolysis Strategy of Enaminones
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A novel heterogeneous catalytic hydrogenation-hydrogenolysis strategy has been developed for the α-methylation of ketones via enaminones using DMF dimethyl acetal as carbon source. This strategy provides a very convenient route to α-methylated ketones using a variety of ketones without any base or oxidant. (Chemical Equation Presented).
- Borah, Ashwini,Goswami, Limi,Neog, Kashmiri,Gogoi, Pranjal
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p. 4722 - 4728
(2015/05/13)
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- A versatile and one-pot strategy to synthesize ?±-amino ketones from benzylic secondary alcohols using N -bromosuccinimide
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A metal-free one-pot strategy has been developed for the first time to synthesize pharmaceutically important ?±-amino ketones from readily available benzylic secondary alcohols and amines using N-bromosuccinimide. This new reaction proceeds via three consecutive steps involving oxidation of alcohols, ?±-bromination of ketones, and nucleophilic substitution of ?±-bromo ketones to give ?±-amino ketones. Importantly, this novel one-pot greener reaction avoids direct usage of toxic and corrosive bromine. This methodology has been employed efficiently to synthesize pharmaceutically important amfepramone and pyrovalerone in a single step.
- Guha, Somraj,Rajeshkumar, Venkatachalam,Kotha, Surya Srinivas,Sekar, Govindasamy
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supporting information
p. 406 - 409
(2015/03/04)
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- Design of novel chiral N,N,O-tridentate phenanthroline ligands and their application to enantioselective addition of organozinc reagents to aldehydes
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The novel N,N,O-tridentate phenanthroline ligand (BinThro) bearing an axially chiral binaphthyl backbone prepared from BINOL was found to be an effective chiral catalyst for enantioselective addition of diethylzinc to aromatic aldehydes with high enantios
- Naganawa, Yuki,Namba, Tomoya,Aoyama, Tomotaka,Shoji, Kentaro,Nishiyama, Hisao
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p. 13224 - 13227
(2015/05/20)
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- A new pyrrolidine-derived atropisomeric amino alcohol as a highly efficient chiral ligand for the asymmetric addition of diethylzinc to aldehydes
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A highly efficient pyrrolidine-derived atropisomeric amino alcohol, (Sa)-1-[2-diphenylhydroxymethyl-6-(trifluoromethyl)phenyl]-2-(1-pyrrolido)methyl-1H-pyrrole, has been synthesized as a chiral ligand for the enantioselective addition of diethylzinc to some prochiral aldehydes to afford (S)-alcohols. The conversion rates were close to quantitative with good to excellent enantiomeric excesses (up to 95% ee).
- Faigl, Ferenc,Erdélyi, Zsuzsa,Deák, Szilvia,Nyerges, Miklós,Mátrav?lgyi, Béla
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supporting information
p. 6891 - 6894
(2015/02/02)
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- Insights into the asymmetric heterogeneous catalysis in porous organic polymers: Constructing A TADDOL-Embedded chiral catalyst for studying the structure-activity relationship[ ]
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Construction of porous organic polymers (POPs) as asymmetric catalysts remains as an important but challenging task. Herein, we exploit the "bottom-up" strategy to facilely synthesize an α,α, α,α-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL)-based chiral porous polymer (TADDOL-CPP) for highly efficient asymmetric catalysis. Constructed through the covalent linkages among the three-dimensional rigid monomers, TADDOL-CPP possesses hierarchical porous structure, high Brunauer-Emmett-Teller (BET) surface area, together with abundant and uniformly-distributed chiral sites. In the presence of [Ti(OiPr)4], TADDOL-CPP acts as a highly efficient and recyclable catalyst in the asymmetric addition of diethylzinc (Et2Zn) to aromatic aldehydes. Based on the direct observation of the key intermediates, the reaction mechanism has been revealed by solid-state 13C magic-angle spinning (MAS) NMR spectroscopy. In combination with the catalytic testing results, characterization on the working catalyst provides further information for understanding the structure-activity relationship. We suggest that the catalytic activity of TADDOL-CPP is largely affected by the structural rigidity, cooperative catalysis, local chiral environment, and hierarchical porous framework. We expect that the information obtained herein will benefit to the designed synthesis of robust POP catalysts toward practical applications.
- An, Wan-Kai,Han, Man-Yi,Wang, Chang-An,Yu, Si-Min,Zhang, Yuan,Bai, Shi,Wang, Wei
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supporting information
p. 11019 - 11028,10
(2014/12/09)
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- The synthesis of chiral amino diol tridentate ligands and their enantioselective induction during the addition of diethylzinc to aldehydes
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A series of C2-symmetric chiral amino diol tridentate ligands 3a-g were prepared from achiral bulky organolithiums, achiral bulky primary amines, and optically active epichlorohydrin (ECH). The prepared C 2-symmetric chiral amino diol tridentate ligands were capable of inducing enantioselectivity in the model reaction of aromatic and aliphatic aldehydes with diethylzinc with an ee of up to 96%. The enantioselectivity can be modulated by adjusting the steric hindrance of the achiral reagents employed in the synthesis of the chiral ligand. The configuration of the addition product depended on the configuration of the amino diol ligands, which can be simply controlled as desired by using the ECH with the desired configuration during the preparation of the ligand.
- Zhang, An-Lin,Yang, Li-Wen,Yang, Nian-Fa,Liu, Yan-Ling
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p. 289 - 297
(2014/04/03)
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- Novel C2-symmetric chiral O,N,N,O-tetradentate 2,2-bipyridyldiolpropane ligands: Synthesis and application in asymmetric diethylzinc addition to aldehydes
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First synthesis of C2-symmetric chiral O,N,N,O-tetradentate 2,2-bipyridyldiolpropane ligands is described. The Mukaiyama-Michael reaction was applied as an important reaction for the synthesis of 2,2-bipyridylpropane 9. Among the ligands synthesized, ligand 11 exhibits excellent chiral induction (up to 97% ee) in diethylzinc addition to various aldehydes. The use of additional Lewis acid such as Ti(OiPr)4 in diethylzinc addition reaction is not required for the present catalytic system.
- Shih, Yi-Shan,Boobalan, Ramalingam,Chen, Chinpiao,Lee, Gene-Hsian
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p. 327 - 333
(2014/04/03)
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- Chiral porous TADDOL-embedded organic polymers for asymmetric diethylzinc addition to aldehydes
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Two chiral porous organic polymers (CPOPs) were synthesized by linking a TADDOL-embedded building block with arylethynylenes units. The CPOPs are highly stable to thermal treatment, moisture, acidity, and basicity. The dihydroxy groups of TADDOL inside th
- Wang, Xiuren,Zhang, Jie,Liu, Yan,Cui, Yong
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p. 435 - 440
(2014/04/17)
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- Asymmetric addition of triethylaluminium to aromatic aldehydes catalyzed by titanium-(5,5'-Biquinoline-6,6'-Diol) complexes
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A novel convenient procedure for the resolution of 5,5'-biquinoline-6,6'- diol (BIQOL) was achieved by separating the corresponding diastereomeric mixture of (S)-(+)-camphorsulfonates on a semiprepared XDB-C8 column followed by hydrolysis. The efficient asymmetric addition of triethylaluminium to aromatic aldehydes catalyzed by Ti-(+)/(-)BIQOL complexes under mild conditions is described. The reactions led to the formation of 1-arylpropan-1-ol in up to 87.5% ee. Chirality 26:268-271, 2014. 2014 Wiley Periodicals, Inc.
- Chen, Qian,Ou, Jun,Chen, Guo-Shu,Liu, Tian-Hui,Xie, Bin,Liang, Hai-Bo,Xie, Li-Qiong,Chen, Yi-Xin
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p. 268 - 271
(2014/05/06)
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