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Synlett 2003(1): 0112-0114
DOI: 10.1055/s-2003-36240
LETTER
© Georg Thieme Verlag Stuttgart · New York

Oxidative Rearrangement of Ketimines to Amides by MCPBA and BF3·OEt2

So Yeon Kim, 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 9 October 2002
Publication Date:
18 December 2002 (online)

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Abstract

Several amides were obtained by an efficient method from the corresponding alkyl aryl ketimines in high yields. Ketimines are readily prepared from the corresponding ketones. This procedure involves the oxidation of alkyl aryl ketimines with MCPBA with BF3·OEt2. In this reaction, only aryl group of alkyl aryl ketimines was migrated to the electron deficient nitrogen atom.

Key words

oxidative rearrangement - ketimines - ketones - migra­tory aptitude - amides

4

An, G.; Kim, M.; Kim, J. Y.; Rhee, H. Tetrahedron Lett., submitted.

5

General procedure for the preparation of ketimines: To a solution of ketone (3 mmol) in CHCl3 (30 mL) were added amine (3.6 mmol) and molecular sieve (1.0 g) at ambient temperature. After being stirred for a certain period of time, the crude mixture was rinsed with K2CO3-brine solution (3 × 20 mL) and the crude product was concentrated by rotary-evaporation. The purity of crude products was checked by 1H NMR spectroscopy and these were pure enough to use for next reaction.
General procedure for the preparation of amides: To a solution of ketimine (3 mmol) in anhydrous CHCl3 (3 mL) were added MCPBA (72%, 3.6 mmol) in anhydrous CHCl3 (10 mL) and BF3·OEt2 (0.9 mmol) at 0 ºC. The resulting reaction mixture was stirred for 1 h at 0 ºC. The reaction mixture was diluted with CHCl3 (10 mL) and washed with saturated Na2CO3 solution (3 × 20 mL). The organic layer was dried over anhydrous MgSO4 and concentrated by rotary-evaporation. The residue was purified by flash column chromatography (EtOAc/n-hexane = 1:1→5:1, v/v).

7

X-Ray crystallographic data for compounds 4b and 4e have been submitted for deposition at the Cambridge Crystallographic Data Center (CCDC 194994 and 194995).