Methylhydrazine → N-ethyl(tert-butoxy)carbohydrazide

Methylhydrazine (1.415 mL, 26.9 mmol) was added to a solution of tert-butyl 1,3-dioxoisoindolin-2-yl(ethyl)carbamate (example 74A, 5.2 g, 17.91 mmol) in THF (40 mL) at 0° C. and the reaction mixture was stirred at room temperature overnight. A white precipitate formed and was filtered off through a pad of Celite, The filtrate was concentrated in vacuo. The residue was dissolved in ethyl acetate (50 ml) and extracted with 1N HCl (3×30 ml), the acid layer was washed with ethyl acetate (50 ml) and basified to pH 10 by addition of 20% NaOH. The basic solution was then extracted with ethyl acetate (3×50 ml) and the combined organic layers were washed with brine, dried over magnesium sulfate, filtered and concentrated in vacuo to give tert-butyl 1-ethylhydrazinecarboxylate (2.5 g, 87% yield) as colorless oil.