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

TETRAHEDRON LETTERS

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Article

Zattoni, Ingrid F.¹  Guanaes, Lais D.¹  Cerqueira, Leticia B.¹  Pontarolo, Roberto¹  Ducatti, Diogo R. B.²  Duarte, M. Eugenia R.²  Noseda, Miguel D.²  Trindade, Angela C. L. B.¹  Goncalves, Alan G.¹ 

[1] Univ Fed Parana, Dept Farm, Av Lothario Meissner,3400 Jardim Botan, Curitiba, Parana, Brazil

[2] Univ Fed Parana, Dept Bioquim & Biol Mol, POB 19046, Curitiba, Parana, Brazil

关键词: Dihydropyridines;    Reduction;    Imines;    Hydride transfer;   

DOI  :  10.1016/j.tetlet.2019.151129

来源: Elsevier

【 摘 要 】

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 is 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 is under stoichiometric BF3OEt2 could also be successfully applied with additional imine examples and under reductive amination conditions. (C) 2019 Elsevier Ltd. All rights reserved.

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