tert-Butyl carbazate → 1,1-Dimethylethyl 2-[(2-chloro-4-fluorophenyl)acetyl]hydrazinecarboxylate

A solution of 2-chloro-4-fluorophenylacetyl chloride (10 mmol) in dry DCM (15 ml) was added over 20 min to a mixture of t-butyl carbazate (1.32 g, 10 mmol) and DIPEA (1.77 ml, 10.2 mmol) in dry DCM (20 ml). After stirring for a further 2 h, the mixture was washed with 1M HCl then with aqueous NaHCO3. A white solid precipitated at this point, which was filtered off, washed with water and DCM then dried to yield 1,1-dimethylethyl 2-[(2-chloro-4-fluorophenyl)acetyl]hydrazinecarboxylate (1.94 g).