- Enantioselective Intermolecular C-H Amination Directed by a Chiral Cation
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The enantioselective amination of C(sp3)-H bonds is a powerful synthetic transformation yet highly challenging to achieve in an intermolecular sense. We have developed a family of anionic variants of the best-in-class catalyst for Rh-catalyzed C-H amination, Rh2(esp)2, with which we have associated chiral cations derived from quaternized cinchona alkaloids. These ion-paired catalysts enable high levels of enantioselectivity to be achieved in the benzylic C-H amination of substrates bearing pendant hydroxyl groups. Additionally, the quinoline of the chiral cation appears to engage in axial ligation to the rhodium complex, providing improved yields of product versus Rh2(esp)2 and highlighting the dual role that the cation is playing. These results underline the potential of using chiral cations to control enantioselectivity in challenging transition-metal-catalyzed transformations.
- Fanourakis, Alexander,Paterson, Kieran J.,Phipps, Robert J.,Williams, Benjamin D.
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supporting information
p. 10070 - 10076
(2021/07/21)
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- Carbocation Catalyzed Bromination of Alkyl Arenes, a Chemoselective sp3 vs. sp2 C?H functionalization.
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The versatility of the trityl cation (TrBF4) as a highly efficient Lewis acid organocatalyst is demonstrated in a light induced benzylic brominaion of alkyl-arenes under mild conditions. The reaction was conducted at ambient temperature under common hood light (55 W fluorescent light) with catalyst loadings down to 2.0 mol% using N-bromosuccinimide (NBS) as the brominating agent. The protocol is applicable to an extensive number of substrates to give benzyl bromides in good to excellent yields. In contrast to most previously reported strategies, this protocol does not require any radical initiator or extensive heating. For electron-rich alkyl-arenes, the trityl ion catalyzed bromination could be easily switched between benzylic sp3 C?H functionalization and arene sp2 C?H functionalization by simply alternating the solvent. This chemoselective switch allows for high substrate control and easy preparation of benzyl bromides and bromoarenes, respectively. The chemoselective switch was also applied in a one-pot reaction of 1-methylnaphthalene for direct introduction of both sp3 C?Br and sp2 C?Br functionality. (Figure presented.).
- Ni, Shengjun,El Remaily, Mahmoud Abd El Aleem Ali Ali,Franzén, Johan
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supporting information
p. 4197 - 4204
(2018/09/25)
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- 3-Substituted phenylalanines as selective AMPA- and kainate receptor ligands
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On the basis of X-ray structures of ionotropic glutamate receptor constructs in complex with amino acid-based AMPA and kainate receptor antagonists, a series of rigid as well as flexible biaromatic alanine derivatives carrying selected hydrogen bond acceptors and donors have been synthesized in order to investigate the structural determinants for receptor selectivity between AMPA and the GluR5 subtype of kainate receptors. Compounds selective for either GluR5 or AMPA receptors were identified. One particular substituent position appeared to be of special importance for control of ligand selectivity. Using molecular modeling the observed structure-activity relationships at AMPA and GluR5 receptors were deduced.
- Szymanska, Ewa,Pickering, Darryl S.,Nielsen, Birgitte,Johansen, Tommy N.
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experimental part
p. 6390 - 6401
(2011/03/17)
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- Lead-discovery of bis-aromatic alkynes: A novel class of herbicides
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The search for new active molecules with novel modes of action and desirable physical properties is an ongoing endeavour.[1,2] This publication describes the follow-up chemistry of a biological hit discovered in the screening system of Novartis
- Glock, Jutta,Allen, James,Niderman, Thierry,Haas, Hans Ulrich,Chollet, Renold,Eberle, Martin,Renold, Peter,Lutz, William,Ehrler, Juerg,Valentini, Marian,Walti, Markus,Sieger, Evelyne,Vettiger, Thomas,Brunner, Hans,Penzotti, Julie E.,Grootenhuis, Peter D. J.,Bondy, Steven,Comer, Daniel D.,Cheng, Soan,Steiger, Arthur,Zeller, Martin,Laue, Grit,Friedmann, Adrian,Jacob, Olivier,Nina, Mafalda,Widmer, Hans-Juerg,Kreuz, Klaus,Craig, G. Wayne
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- Double elimination protocol for convenient synthesis of dihalodiphenylacetylenes: Versatile building blocks for tailor-made phenylene-ethynylenes
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Dihalodiphenylacetylenes are conveniently synthesized by a double elimination reaction of β-substituted sulfones which are readily obtained from halogen-substituted benzyl sulfone and benzaldehyde derivatives. Halogens can be incorporated at any desired positions in the diphenylacetylene skeleton simply by choosing the substitution position of the halogen on the aromatic rings of the starting compounds. The diphenylacetylenes with different halogen substituents thus obtained undergo sequential carbon-carbon bond formations due to the different reactivities of the halogens. Thus, various moieties can be incorporated on the diphenylacetylene skeleton at whichever positions so that a variety of tailor-made phenylene-ethynylenes with regulated structure and composition could be designed.
- Orita, Akihiro,Miyamoto, Kazuhiko,Nakashima, Mikio,Ye, Fangguo,Otera, Junzo
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p. 767 - 776
(2007/10/03)
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- Substituted norbornylamino derivatives, processes for their preparation, their use as medicaments or diagnostics, and a medicament comprising them
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The application discloses substituted norbornylamino derivatives, processes for their preparation, their use as medicaments or diagnostics and a medicament comprising them Substituted norbornylamino derivatives having exo-configured nitrogen and an endo-f
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- ORGANIC PHOSPHORUS COMPOUNDS 91. SYNTHESIS AND PROPERTIES OF 1-AMINO-2-ARYLETHYLPHOSPHONIC AND -PHOSPHINIC ACIDS AS WELL AS -PHOSPHINE OXIDES
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The preparation, physical and spectroscopic properties of 1-amino-2-arylethylphosphonic, and -phosphinic acids as well as -phosphine oxides, the phosphorus analogues of phenylalanine are described, and the reactions of 1-amino-2-(4-fluorophenyl)ethylphosphonates with acetals, isocyanides, esters, acid anhydrides, activated aromatic nitro- and halogen compounds, and with N-protected alanine are reported.It is shown that several of the 1-amino-2-arylethylphosphonic acids are strong inhibitors of PAL and anthocyanin synthesis and also are quite active botryticides.Among the active compounds were 1-amino-2-(4-fluorophenyl)ethylphosphonic acid, 3f, and the methyl-substituted compounds 3k, 3l, and 3m.The fluoroderivative 3f was also effective as a seed-dressing agent in barley showing a 100percent protection against the fungus Fusarium nivale at 600 ppm.
- Maier, Ludwig
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