- Biomimetic reductive amination under the continuous-flow reaction conditions
-
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
-
experimental part
p. 261 - 265
(2010/04/05)
-
- Biomimetic reductive amination of fluoro aldehydes and ketones via [1,3]-proton shift reaction. Scope and limitations
-
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.
- Ono, Taizo,Kukhar, Valery P.,Soloshonok, Vadim A.
-
p. 6563 - 6569
(2007/10/03)
-
- AZOMETHINE-AZOMETHINE ISOMERIZATION IN THE SERIES OF FLUORINE-CONTAINING N-BENZYLIMINES
-
The reaction of N-benzyltriphenylphosphine imide with fluorine-containing carbonyl compounds leads to the corresponding N-benzylimines.The latter readily isomerize under the influence of bases to N-benzylidene derivatives.
- Soloshonok, V. A.,Gerus, I. I.,Yagupol'skii, Yu. L.,Kukhar', V. G.
-
p. 895 - 899
(2007/10/02)
-