Triethylamine → 3-(5-Chloro-pentanoylamino)-5-nitro-benzoic acid methyl ester

5-Chlorovaleryl chloride (2.64 g, 17 mmol, 1.1 equiv) in CH2Cl2 (5 ml) was added over 2 min to a stirred solution of 3-amino-5-nitro-benzoic acid methyl ester (D1) (3 g, 15.3 mmol, 1 equiv) and NEt3 (2.6 ml, 18 mmol, 1.2 equiv) in CH2Cl2 (30 ml). The resulting mixture was stirred for 1 h at room temperature then washed with 2N aqueous HCl solution, dried over MgSO4 and concentrated in vacuo. The residue was triturated with CH2Cl2 to give 3-(5-Chloro-pentanoylamino)-5-nitro-benzoic acid methyl ester D3 (6 g, 112%) as a brown oil.