- Mechanistically Guided One Pot Synthesis of Phosphine-Phosphite and Its Implication in Asymmetric Hydrogenation
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Although hybrid bidentate ligands are known to yield highly enantioselective products in asymmetric hydrogenation (AH), synthesis of these ligands is an arduous process. Herein, a one pot, atom-economic synthesis of a hybrid phosphine-phosphite (L1) is reported. After understanding the reactivity difference between an O-nucleophile versus C-nucleophile, one pot synthesis of Senphos (L1) was achieved (72 %). When L1 was treated with [Rh], 31P NMR revealed bidentate coordination to Rh. Senphos, in the presence of rhodium, catalyzes the AH of Methyl-2-acetamido-3-phenylacrylate and discloses an unprecedented turn over frequency of 2289, along with excellent enantio-selectivity (92 %). The generality is demonstrated by hydrogenating an array of alkenes. The AH operates under mild conditions of 1–2 bar H2 pressure, at room temperature. The practical relevance of L1 is demonstrated by scaling-up the reaction to 1 g and by synthesizing DOPA, a drug widely employed for the treatment of Parkinson's disease. Computational insights indicate that the R isomer is preferred by 3.8 kcal/mol over the S isomer.
- Sen, Anirban,Kumar, Rohit,Pandey, Swechchha,Vipin Raj,Kumar, Pawan,Vanka, Kumar,Chikkali, Samir H.
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supporting information
(2022/01/11)
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- Topology-Based Functionalization of Robust Chiral Zr-Based Metal-Organic Frameworks for Catalytic Enantioselective Hydrogenation
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The design and development of robust and porous supported catalysts with high activity and selectivity is extremely significant but very challenging for eco-friendly synthesis of fine chemicals and pharmaceuticals. We report here the design and synthesis of highly stable chiral Zr(IV)-based MOFs with different topologies to support Ir complexes and demonstrate their network structures-dependent asymmetric catalytic performance. Guided by the modulated synthesis and isoreticular expansion strategy, five chiral Zr-MOFs with a flu or ith topology are constructed from enantiopure 1,1′-biphenol-derived tetracarboxylate linkers and Zr6, Zr9, or Zr12 clusters. The obtained MOFs all show high chemical stability in boiling water, strongly acidic, and weakly basic aqueous solutions. The two flu MOFs featuring the dihydroxyl groups of biphenol in open and large cages, after sequential postsynthetic modification with P(NMe2)3 and [Ir(COD)Cl]2, can be highly efficient and recyclable heterogeneous catalysts for hydrogenation of α-dehydroamino acid esters with up to 98% ee, whereas the three ith MOFs featuring the dihydroxyl groups in small cages cannot be installed with P(NMe2)3 to support the Ir complex. Incorporation of Ir-phosphorus catalysts into Zr-MOFs leads to great enhancement of their chemical stability, durability, and even stereoselectivity. This work therefore not only advances Zr-MOFs as stable supports for labile metal catalysts for heterogeneous asymmetric catalysis but also provides a new insight into how highly active chiral centers can result due to the framework topology.
- Jiang, Hong,Zhang, Wenqiang,Kang, Xing,Cao, Ziping,Chen, Xu,Liu, Yan,Cui, Yong
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supporting information
p. 9642 - 9652
(2020/07/02)
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- Silver-Promoted Direct Phosphorylation of Bulky C(sp2)-H Bond to Build Fully Substituted β-Phosphonodehydroamino Acids
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A general and practical cross-dehydrogenative coupling protocol between readily available trisubstituted α,β-dehydro α-amino carboxylic esters and H-phosphites is described. This C(sp2)-H phosphorylation reaction proceeds with absolute Z-selectivity promoted by silver salt in a radical relay manner. The bulky tetrasubstituted β-phosphonodehydroamino acids were obtained in grams and added new modules to the toolkit for peptide modifications.
- Cao, Hao-Qiang,Liu, Hao-Nan,Liu, Zhe-Yuan,Qiao, Baokun,Zhang, Fa-Guang,Ma, Jun-An
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supporting information
p. 6414 - 6419
(2020/09/02)
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- Chiral bisphosphine ligands based on quinoline oligoamide foldamers: application in asymmetric hydrogenation
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A series of chiral bisphosphine ligands were designed and synthesized based on single-handed quinoline oligoamide foldamers. The bisphosphine ligands can coordinate with Rh(cod)2BF4 in a 1 : 1 stoichiometry and the resulted chiral Rh(i) catalysts were applied in the asymmetric hydrogenation of α-dehydroamino acid esters, in which excellent conversions and promising levels of enantioselectivity were achieved.
- Zheng, Lu,Zheng, Dan,Wang, Yanru,Yu, Chengyuan,Zhang, Kun,Jiang, Hua
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supporting information
p. 9573 - 9577
(2019/11/20)
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- An Atropos Biphenyl Bisphosphine Ligand with 2,2′-tert-Butylmethylphosphino Groups for the Rhodium-Catalyzed Asymmetric Hydrogenation of Enol Esters
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This is an update of our previous work concerning the development of Atropos biphenyl bisphosphine ligands. An unexpected Atropos structural property was confirmed by single crystal X-ray diffraction and this result is consistent with the computational calculations described in our previous work. This P-stereogenic bisphosphine ligand possessing a biphenyl backbone and 2,2′-tert-butylmethylphosphino groups has been applied to the Rh-catalyzed asymmetric hydrogenation of enol esters, which has not been widely studied and can be used for the synthesis of several important bioactive compounds. Although there is room for further improvement in enantioselectivity, the results reported herein provide a further understanding of such types of ligands. (Figure presented.).
- Jia, Jia,Fan, Dongyang,Zhang, Jian,Zhang, Zhenfeng,Zhang, Wanbin
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supporting information
p. 3793 - 3800
(2018/09/20)
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- Orthopalladation of GFP-Like Fluorophores Through C–H Bond Activation: Scope and Photophysical Properties
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The luminescence of oxazolones R1-C6H4CH=CC(O)O-CN(R2) (1a–1j) and imidazolones R1-C6H4CH=CC(O)NR3CN(R2) (1k–1q) has been examined. The new GFP-like imidazo
- Collado, Sandra,Pueyo, Alejandro,Baudequin, Christine,Bischoff, Laurent,Jiménez, Ana Isabel,Cativiela, Carlos,Hoarau, Christophe,Urriolabeitia, Esteban P.
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p. 6158 - 6166
(2018/11/23)
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- Single-Biocatalyst Synthesis of Enantiopure d-Arylalanines Exploiting an Engineered d-Amino Acid Dehydrogenase
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A practical and efficient biocatalytic synthesis of aromatic d-amino acids has been developed, based on the reductive amination of the corresponding α-keto acids via a recombinant whole cell system composed of an engineered dehydrogenase and cofactor recycling apparatus. The reaction was shown to give excellent enantioselectivity (≥98%) and good yields at the preparative scale across a broad range of substrates. Additionally, the structure of the variant enzyme was solved to allow rationalisation of the observed reaction rates. The engineered whole cell catalyst was also used to mediate the production of d-phenylalanine derivatives from racemic mixtures and cheaper l-amino acids by combining it with an enantiocomplementary deaminase. (Figure presented.).
- Parmeggiani, Fabio,Ahmed, Syed T.,Thompson, Matthew P.,Weise, Nicholas J.,Galman, James L.,Gahloth, Deepankar,Dunstan, Mark S.,Leys, David,Turner, Nicholas J.
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supporting information
p. 3298 - 3306
(2016/10/20)
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- Cation-triggered switchable asymmetric catalysis with chiral aza-crownphos
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An aza-crown ether, modified phosphoramidite ligand, has been designed and synthesized. The ON/OFF reversible switch of catalytic activity for its rhodium catalyst was thoroughly investigated in the asymmetric hydrogenation of dehydroamino acid esters modulated by host-guest interactions. In the OFF state, the catalyst is almost inactive (less than 1% conversion) because of the formation of an intermolecular sandwich complex by two aza-crown ether moities and the cationic rhodium metal center. In using alkali-metal-cations as the trigger, the catalytic activity was turned ON and consequently resulted in full conversions and excellent enantioselectivities (up to 98% ee).
- Ouyang, Guang-Hui,He, Yan-Mei,Li, Yong,Xiang, Jun-Feng,Fan, Qing-Hua
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supporting information
p. 4334 - 4337
(2015/04/14)
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- Microwave-assisted synthesis and antimicrobial screening of new imidazole derivatives bearing 4-thiazolidinone nucleus
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A new series of compounds 2-((1-(4-(4-arylidene-2-methyl-5-oxo-4,5-dihydro- 1H-imidazol-1-yl)phenyl)ethylidene)hydrazono)thiazolidin-4-ones (4a-o) have been synthesized under conventional and microwave irradiation method. All compounds were characterized by IR, 1H NMR, 13C NMR and mass spectra. Newly synthesized compounds were screened for their antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger and Aspergillus clavatus by bioassays, namely serial broth dilution. The synthesized compounds showed potent antimicrobial activity against tested microorganisms. Compounds 4h, 4j, 4m and 4n were the most potent amongst tested compounds.
- Desai,Joshi,Rajpara,Vaghani,Satodiya
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p. 1893 - 1908
(2013/07/26)
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- Facile synthesis of 4-arylidene-5-imidazolinones as synthetic analogs of fluorescent protein chromophore
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A facile and effective synthesis for a wide variety of 4-arylidene-5- imidazolinone derivatives was developed. 4-Arylidene-5-oxazolinones were prepared by Erlenmeyer azlactone synthesis from N-acylglycines and arylaldehydes. The ring-opening reactions of the 4-arylidene-5-oxazolinones with primary amines afforded 2-acylamino-3-arylacrylamides in excellent yields. A new dehydrative cyclization of the 2-acylamino-3-arylacrylamides in pyridine under reflux furnished the corresponding 4-arylidene-5-imidazolinones in good yields.
- Lee, Cheng-Yu,Chen, Yun-Chung,Lin, Hao-Chun,Jhong, Yuandong,Chang, Chih-Wei,Tsai, Ching-Hua,Kao, Chai-Lin,Chien, Tun-Cheng
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supporting information; experimental part
p. 5898 - 5907
(2012/09/07)
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- Synthetic GFP chromophore and control of excited-state proton transfer in DNA: An alternative concept for fluorescent DNA labels with large apparent stokes' shifts
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Synthetic GFP-like chromophores bearing an ortho-phenol group instead of the para-phenol group of natural GFP can mimic the hydrogen bonding network in the protein by an intramolecular hydrogen bond to the imidazolone group. This hydrogen bond influences
- Wenge, Ulrike,Wagenknecht, Hans-Achim
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experimental part
p. 502 - 508
(2011/04/22)
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- Phenoxypropylamine compounds
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The present invention relates to a phenoxypropylamine compound of the formula (I) wherein each symbol is as defined in the specification, an optically active compound thereof or a pharmaceutically acceptable salt thereof and hydrates thereof, which simultaneously show selective affinity for and antagonistic activity against 5-HT1A receptor, as well as 5-HT reuptake inhibitory activity, and can be used as antidepressants quick in expressing an anti-depressive effect.
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- Chemocontrolled reduction of aromatic α-ketoesters by NaBH4: Selective synthesis of α-hydroxy esters or 1,2-diols
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α-Hydroxyesters 5a-g or diols 6a-g have been obtained in high yields by reduction of aromatic α-ketoesters 4 once or twice respectively by using NaBH4 as the reducer under suitable conditions. The use of a solvent that does not interact with the reagent allowed the double reduction to occur with only a slight excess of borohydride in very mild conditions.
- Dalla, Vincent,Cotelle, Philippe,Catteau, Jean Pierre
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p. 1577 - 1580
(2007/10/03)
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- Synthesis of some new 2-methyl-4-(substituted benzylidene) 1-phenyl-1,2,4 triazolo [3,4,-b] 1,3,4 thiadiazole as potential AChE inhibitory agents
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4-(1-aminophenyl) -1,2,4 - triazolo [3,4,-b] 1,3,4-thiadiozole (2) was prepared by treatment of 4-(1-aminophenyl)-5-mercapto-4-amino-1,2,4-S-triazole with carbondisulfide and KOH in methanol. This on further reaction with different 2-methyl-4-(substituted
- Sen,Shanker
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p. 465 - 467
(2007/10/03)
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