158388-65-9Relevant academic research and scientific papers
The effect of substituents on the feasibility of azomethine - Azomethine isomerization: New synthetic opportunities for biomimetic transamination
Soloshonok, Vadim A.,Ono, Taizo
, p. 14701 - 14712 (1996)
The azomethine - azomethine isomerization of the Schiff bases derived from fluoroalkyl carbonyl compounds and arylmethylamines has been studied as a function of substitution on the amine site. The present study indicates that regardless of the nature of the substitution, the position of the isomerization equilibrium is overwhelmingly controlled by the electron-withdrawing effect of the perfluoroalkyl group, while the reaction rate strongly depends on both CH acidity and steric availability of the transferring proton. Specifically, we have found that the presence of electron-releasing substituent on the phenyl of the benzylamine site largely retards the isomerization of the corresponding imines. In contrary, azomethine-azomethine isomerizations of the imines derived from the benzylamines containing electron-withdrawing substituent on-the phenyl ring or picolylamines, possessing electron-deficient pyridine ring, occur with remarkably higher reaction rates as compared with the established isomerizations of N-benzylimines. In particular, the use of 4-picolylamine allows for truly biomimetic one-stage transamination of fluorocarbonyl compounds to afford the Schiff bases of the corresponding amines. The exciting synthetic aspects of this finding are demonstrated by the improved procedure for transamination of certain fluoroalkyl carbonyl compounds representing aldehydes, ketones, and β-keto carboxylic acids.
Chemoenzymatic dynamic kinetic resolution of α-trifluoromethylated amines: Influence of substitutions on the reversed stereoselectivity
Cheng, Guilin,Xia, Bo,Wu, Qi,Lin, Xianfu
, p. 9820 - 9828 (2013/09/02)
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.
Biomimetic reductive amination of fluoro aldehydes and ketones via [1,3]-proton shift reaction. Scope and limitations
Ono, Taizo,Kukhar, Valery P.,Soloshonok, Vadim A.
, p. 6563 - 6569 (2007/10/03)
A systematic study of azomethine-azomethine isomerizations of the N-benzylimines 2, derived from fluorinated aldehydes or ketones and benzylamine, has been made. The results reveal that, in sharp contrast to hydrocarbon analogs, fluorinated imines of 2 in triethylamine solution undergo isomerizations to give the corresponding N-benzylidene derivatives 5 (for 5/2 K > 32) in good isolated yields. The rates of the isomerizations depend on the starting imine structures and increase in the following order: aryl perfluoroalkyl ketimine 2m, per(poly)fluoroalkyl aldimine 2a,d-g, perfluoroaryl aldimine 2h, alkyl perfluoroalkyl ketimine 2i,j. The presence of chlorine or bromine atoms in the α-position to the C=N double bond of the starting imine favors a dehydrohalogenation reaction, giving rise to unsaturated products 6-9. The azomethine-azomethine isomerization was studied and proven to proceed essentially (>98%) intramolecularly with isotope exchange experiments. High chemical yields, the simplicity of the experimental procedure, and the low cost of all reagents employed make this biomimetic transamination of fluorocarbonyl compounds a practical method for preparing fluorine-containing amines of biological interest.
A practical route to fluoroalkyl- and fluoroarylamines by base-catalyzed [1,3]-proton shift reaction
Soloshonok,Soloshonok, Vadim A.,Kirilenko,Kirilenko, Alexander G.,Kukhar,Kukhar, Valery P.,Resnati,Resnati, Giuseppe
, p. 3119 - 3122 (2007/10/02)
The base-catalyzed [1,3]-proton shift reaction is shown to be an efficient general approach to fluoroalkyl and fluoroaryl amines starting from appropriate carbonyl compounds and benzylamine.
