Diisopropylethylamine → tert-Butyl 2-(2-fluoro-4-nitrobenzoyl)-2-methylhydrazinecarboxylate

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Under argon and at RT, 17.1 g (53.4 mmol, 1.3 eq.) of (benzotriazol-1-yloxy)bisdimethylaminomethylium fluoroborate and 21.4 ml (123.1 mol, 3.0 eq.) of N,N-diisopropylethylamine were added to a solution of 9.1 g (49.3 mmol, 1.2 eq.) of 2-fluoro-4-nitrobenzoic acid in 200 ml of DMF, and the mixture was stirred at RT for 20 min. A solution of 12.5 g (purity 48%, 41 mmol) of tert-butyl 2-methylhydrazinecarboxylate in 50 ml of DMF was added, and the reaction mixture was stirred at RT for 6 h. After removal of the DMF under reduced pressure and addition of water/ethyl acetate and phase separation, the organic phase was washed with 10% aqueous citric acid and with saturated aqueous sodium chloride solution, dried (sodium sulphate), filtered and concentrated under reduced pressure. The crude product was purified by flash chromatography (silica gel 60, mobile phase: cyclohexane/ethyl acetate mixtures). Yield: 8.35 g (65% of theory)

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