6426-26-2Relevant articles and documents
Composition and structure of activated complexes in stereoselective deprotonation of cyclohexene oxide by a mixed dimer of chiral lithium amide and lithiated imidazole
Pettersen, Daniel,Diner, Peter,Amedjkouh, Mohamed,Ahlberg, Per
, p. 1607 - 1613 (2004)
Stereoselective deprotonation of cyclohexene oxide, using a mixed dimer built of the chiral lithium amide, lithium (1R,2S)-N-methyl-1-phenyl-2- pyrrolidinyl-propanamide, and 2-lithio-1-methylimidazole, has been studied. The composition of the rate limiting activated complex was determined by kinetics to be built from one mixed dimer molecule and one epoxide molecule. Based on this knowledge computational chemistry has been applied to gain insight into possible structures of the activated complexes.
On the novel function of the additive DBU. Catalytic stereoselective deprotonation by a mixed dimer of lithiated DBU and a chiral lithium amide
Pettersen, Daniel,Amedjkouh, Mohamed,Nilsson Lill, Sten O.,Ahlberg, Per
, p. 1397 - 1405 (2002)
The additive DBU is used to increase the selectivity and reactivity of e.g. chiral lithium amides in both catalysed and non-catalysed asymmetric syntheses. This has been attributed to the coordinating ability of DBU favoring more reactive aggregates. However, we have found that LDA in THF deprotonates DBU to yield lithiated DBU (1) as shown by multinuclear NMR studies. Furthermore, compound 1 is found to form a mixed dimer (5) with e.g. the norephedrine-derived chiral lithium amide 2. Results of an investigation of the stereoselectivity of this novel reagent in the epoxide deprotonation are also reported. Computational studies using PM3 and DFT show possible structures of 1 and 5 in line with the NMR results. In addition, the role of THF and DBU in the solvation of the aggregates has been investigated by computational modelling and favoured complexes in the equilibria between homo- and heterocomplexes are also reported.
CHOLINE METABOLISM INHIBITORS
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Page/Page column 50; 102-103, (2020/07/05)
The present disclosure relates to compounds, compositions and methods for inhibiting choline metabolism, e.g., conversion of choline to trimethylamine. Disclosed herein are compounds, compositions, and methods for inhibiting choline metabolism, e.g., conversion of choline to TMA. Also disclosed herein are compounds, methods and compositions for inhibiting choline metabolism by gut microbiota resulting in reduction in the formation of trimethylamine (TMA) and trimethylamine N-oxide (TMAO).
Enantioselective Hydrogenation of Ketones using Different Metal Complexes with a Chiral PNP Pincer Ligand
Garbe, Marcel,Wei, Zhihong,Tannert, Bianca,Spannenberg, Anke,Jiao, Haijun,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
supporting information, p. 1913 - 1920 (2019/03/13)
The synthesis of different metal pincer complexes coordinating to the chiral PNP ligand bis(2-((2R,5R)-2,5-dimethyl-phospholanoethyl))amine is described in detail. The characterized complexes with Mn, Fe, Re and Ru as metal centers showed good activities regarding the reduction of several prochiral ketones. Comparing these catalysts, the non-noble metal complexes produced best selectivities not only for aromatic substrates, but also for different kinds of aliphatic ones leading to enantioselectivities up to 99% ee. Theoretical investigations elucidated the mechanism and rationalized the selectivity. (Figure presented.).
Manganese(I)-Catalyzed Enantioselective Hydrogenation of Ketones Using a Defined Chiral PNP Pincer Ligand
Garbe, Marcel,Junge, Kathrin,Walker, Svenja,Wei, Zhihong,Jiao, Haijun,Spannenberg, Anke,Bachmann, Stephan,Scalone, Michelangelo,Beller, Matthias
supporting information, p. 11237 - 11241 (2017/09/02)
A new chiral manganese PNP pincer complex is described. The asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (30–40 °C, 4 h, 30 bar H2). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivity (e.r. up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry.
