TETRAHEDRON LETTERS Tetrahedron Letters 43 (2002) 647–651 Pergamon N -Acylation of amides with acid anhydrides by way of dual activation using MgBr 2 ·OEt 2 Shinji Yamada,* Setsuko Yaguchi and Kaori Matsuda Department of Chemistry, Faculty of Science, Ochanomizu University, Bunkyo -ku, Tokyo 112 -8610, Japan Received 18 October 2001; revised 14 November 2001; accepted 16 November 2001 Abstract—A new practical method for the N-acylation of amides is described. Acylation of various amides with acid anhydrides in the presence of MgBr 2 ·OEt 2 gave the corresponding N-acylamides in good to moderate yields. The present method is applicable to amides that are labile to acids or bases. © 2002 Elsevier Science Ltd. All rights reserved. An acyclic N -acylamide core constitutes various natural products such as immunosuppressant microcolin A and B, 1 anticancer agent dolastatin 15, 2 antibiotic alth- iomycin, 3 antifeedant ypaoamide, 4 and neurotoxin jano- lusimide. 5 In addition, N -acyloxazolidinone, 6 N -acylsultam 7 and related compounds, which have been utilized in various asymmetric syntheses, also possess an N -acylamide core. To construct these N -acylamide struc- tures, activation of amides and/or acyl donors is generally required, since the nitrogen atom of amides is less basic than that of the corresponding amines due to amide resonance. Reported methods for the N -acylation by a combination of amides and acyl donors are as follows: lithiated amide–acyl chloride, 8 trimethylsilylated amide– acyl chloride, 9,10 phosphoramidate–carboxylic acid, 11 lithiated amide–pentafluorophenyl esters, 12,13 amide– MeMgBr–acyl chloride, 14 amide–p -toluenesulfonic acid– enol ester, 15 amide–LiCl–acid anhydride, 16 amide– sulfuric acid–acid anhydride. 17 However, these methods are not always applicable to amides that are labile to acids and bases. 12a,18,19 Therefore, discovery of a more mild method continues to attract the attention of researchers. Keywords : amides; acylation; lactams; imides; magnesium and compounds. * Corresponding author. Tel.: +81-3-5978-5349; fax: +81-3-5978-5715; e-mail: yamada@cc.ocha.ac.jp 0040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved. PII:S0040-4039(01)02208-0