1,4-Dihydropyridine/BF3OEt2 for the reduction of imines: Influences of the amount of added BF3OEt2 and the substitution at N-1 and C-4 of the dihydropyridine ring |
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Authors: | Ingrid F Zattoni Lais D Guanaes Letícia B Cerqueira Roberto Pontarolo Diogo RB Ducatti M Eugênia R Duarte Miguel D Noseda Angela CLB Trindade Alan G Gonçalves |
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Institution: | 1. Departamento de Farmácia, Universidade Federal do Paraná, Av. Lothario Meissner, 3400, Jardim Botânico, Curitiba, Paraná, Brazil;2. Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, PO Box 19046, Curitiba, Paraná, Brazil |
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Abstract: | We have evaluated four 1,4-dihydropyridines (DHPs 1a, 1b, 1c and 1d) as reducing agents, which presented free (hydrogenated) or phenyl-substituted N-1 and C-4 positions of the DHP ring. Reactions combining each of the DHP and different amounts of BF3OEt2 were evaluated for the reduction of imine 2a (N-benzylideneaniline). DHP simultaneously substituted at N-1 and C-4 (1a), and DHP substituted at C-4 (1b) gave lower yields for reduction of 2a in comparison with DHPs 1c and 1d (both unsubstituted at the C-4 position). By evaluating the amount of added BF3OEt2 to the reaction mixture, we have found that DHP 1c (substituted at N-1) provided its best yield for amine 3a (82%) when associated with stoichiometric amounts BF3OEt2, while DHP 1d (N-1- and C-4-unsubstituted derivative) was more effective (90% yield) with catalytic quantities of the Lewis acid. The reaction system using DHP 1c under stoichiometric BF3OEt2 could also be successfully applied with additional imine examples and under reductive amination conditions. |
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Keywords: | Corresponding author Dihydropyridines Reduction Imines Hydride transfer |
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