To a solution of ethyl 3-bromo-5-nitro-4-[(trifluoroacetyl)amino]benzoate (D214) (12.0 g, 31.3 mmol, 1 equiv) in CH3CN (100 ml) was added K2CO3 (5.6 g, 40 mmol, 1.3 equiv) and 1-bromo-3-methyl-2-butene (5.1 ml, 43.8 mmol, 1.4 equiv) and the resulting mixture was refluxed for 1 h then cooled to room temperature. The precipitate formed was filtered off through a pad of celite and washed with CH3CN. The combined organic layers were concentrated in vacuo and the residue diluted with AcOEt. The organic layer was washed with brine, dried over MgSO4 and concentrated in vacuo. Purification of the residue by flash chromatography on silica gel (iso-hexane/AcOEt: 9/1 to 4/1) gave ethyl 3-bromo-4-[(3-methyl-2-buten-1-yl)(trifluoroacetyl)amino]-5-nitrobenzoate (D215) (12.9 g, 91%) as an orange oil.
