- Economical and practical strategies for synthesis of α-trifluoromethylated amines
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A powerful approach to synthesize α-trifluoromethylated amines has been developed. The method is operationally simple, broad in substrate scope and amenable to scale-up using trifluoroacetic anhydride. Meanwhile, the strategy not only provided a versatile approach to synthesize α-trifluoromethylated amines but also provides a new method for exploring the new reactivity of trifluoroacetic anhydride.
- Jiang,Cheng,Yuan
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p. 2406 - 2408
(2016/05/19)
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- Chemoenzymatic dynamic kinetic resolution of α-trifluoromethylated amines: Influence of substitutions on the reversed stereoselectivity
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Enzymatic resolution of α-trifluoromethylated amines via kinetic resolution (KR), dynamic kinetic resolution (DKR) employing CALB-Pd/Al 2O3, and a one-pot sequential process of KR/DKR/KR was investigated comparatively for the first time. Although CALB-catalyzed KR of α-trifluoromethylated amines with substituents of methyl (1a), isopropyl (1c), phenyl (1d) and benzyl group (1e) can provide good stereoselectivity factors E from 31 to >200 respectively, DKR and sequential process of KR/DKR/KR possess better practical application potential because of the higher conversion (62%-84%) and the similar enantiomeric excesses (90%-99%). The enantiopreference and inversion for the α-trifluoromethylated amines displayed by CALB were observed and explained by docking modes. Namely, for 1,1,1-trifluoro-2-propylamine (1a), the product amide with R-configuration was obtained, and the enantiopreference was converted to S for the amines (1b-1e) with substituents larger than methyl group. The catalysts recycle, and scale-up experiments were demonstrated successfully. All these results indicated the high efficiency and green feature of this enzymatic process, and its application significance.
- Cheng, Guilin,Xia, Bo,Wu, Qi,Lin, Xianfu
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p. 9820 - 9828
(2013/09/02)
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- Biomimetic reductive amination under the continuous-flow reaction conditions
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This study present a full account of continuous-flow reaction conditions for biomimetic reductive amination of fluorinated carbonyl compounds to corresponding amines and amino acids of biomedical importance. We demonstrate that simple silica-adsorbed DBU can be used as efficient catalysts for on-column 1,3-proton shift reaction, a key transformation in the biomimetic reductive amination process. This new on-column process features operationally convenient conditions, higher chemical yields, enantioselectivity and purity of the corresponding products as compared with traditional in-flask reactions. Moreover the removal of base-catalyst, the most delicate problem of the in-flask reactions, is not an issue in the on-column process, as the silica-adsorbed DBU or polymer-bound guanidine remains on the column and can be reused. This feature renders the overall process substantially more economical and synthetically efficient, in particular, for large-scale synthesis of the corresponding fluorinated amines and amino acids target.
- Soloshonok, Vadim A.,Catt, Hector T.,Ono, Taizo
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body text
p. 261 - 265
(2010/04/05)
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- Deamination Reactions, 43 - The Effect of Trifluoromethyl Groups on the Reactivity of Aliphatic Diazonium Ions and Carbocations
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Various trifluoroalkanamines (9, 26, 35, 38, 45, 56, and 67) have been prepared and diazotized (water, pH 3.5) to probe the effect of trifluoromethyl groups on the reactivity of aliphatic diazonium ions.The product distributions reveal that α-CF3 groups enhance inverting displacement and enforce rearrangement (hydride shifts) separating the positive charge from CF3.Migrations of the positive charge from the β- to the γ-position are less strongly promoted than those from α to β.Enhancement factors of ca. 15 (α -> β) and 4 (β -> γ) may be derived by comparison with analogous alkanediazonium ions.The positive charge does not migrate in the reverse direction (β -> α) except for minor amounts of a pinacolic rearrangement (68 -> 7).A migration of the positive charge from γ to β has been detected with 36 but a tenfold decrease as compared to the analogous butanediazonium ion 37 is indicated.All observations are reasonably explained in terms of the relative stabilities of the intermediate trifluoroalkyl cations.
- Gassen, Karl-Rudolf,Kirmse, Wolfgang
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p. 2233 - 2248
(2007/10/02)
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