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Synlett 2003(6): 0876-0878
DOI: 10.1055/s-2003-38754
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

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

Gwang-il An, Hakjune Rhee*
Department of Chemistry, Hanyang University, Ansan, Kyunggi-Do 425-791, Korea
Fax: +82(31)4073863; e-Mail: hrhee@hanyang.ac.kr;
Further Information

Publication History

Received 27 February 2003
Publication Date:
17 April 2003 (online)

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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.

Key words

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

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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).