Oxidation of N-Benzylaldimines to N-Benzylamides by MCPBA and BF₃⟨OEt₂

Abstract

N-Benzylamides were obtained from the corresponding N-benzylaldimines in high yields. N-Benzylaldimines are readily prepared from the corresponding aldehydes with benzylamine. This procedure involves the oxidation of N-benzylaldimines with MCPBA with BF₃×OEt₂. In this reaction, the reaction presumably follows an internal hydrogen abstraction to provide only N-benzyl­amide.

N-benzylaldimines - aldehydes - peroxy intermediate - fragmentation - N-benzylamides

References

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General Procedure for the Preparation of Amides: To a solution of aldimine (1.024 mmol) in anhyd CHCl₃ (3 mL) were added MCPBA (72%, 1.126 mmol) in anhyd CHCl₃ (3 mL) and BF₃×OEt₂ (0.307 mmol) at 0 °C. The resulting reaction mixture was stirred for a certain period of time at r.t. The reaction mixture was diluted with CHCl₃ (20 mL) and washed with sat. Na₂CO₃ solution (20 mL ¥ 3). The organic layer was dried over anhyd MgSO₄ and concentrated by rotary-evaporation. The residue was purified by pre-loaded flash column chromatography (EtOAc/n-hexane = 1:2-6, v/v).

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X-Ray crystallographic data for compounds 2e and 2m have been submitted for deposition at the Cambridge Crystallographic Data Center (CCDC 200858 and 200859).