Ethyl isothiocyanate → tert-Butyl (ethylcarbamothioyl)carbamate

A solution of tert-butyl carbamate (5.0 g, 42.7 mmol) and isothiocyanatoethane (3.7 mL, 42.7 mmol) in dry DMF (30 mL) was added slowly to a stirred solution of sodium hydride (60% suspension, 1.9 g, 47 mmol) in dry DMF (15 mL) under nitrogen, such that the internal temperature was maintained <5° C. After complete addition the reaction was stirred in an ice bath for 1 h. The cooling bath was removed and the reaction was stirred at RT overnight, and then poured on to ice (25 g) and diluted with water (150 mL). The aqueous mixture was extracted with Et2O (3×100 mL). The combined extracts were washed with brine (1×50 mL), dried (MgSO4), filtered and evaporated. The residue was purified by column chromatography (normal phase, 100 g, Biotage SNAP cartridge KP-Sil, 50 mL per min, gradient 4% to 8% EtOAc in n-hexane) to give the title compound (6.0 g, colourless solid). 1H NMR (400 MHz, CDCl3) δ ppm 1.29 (t, J=7.33 Hz, 3H) 1.50 (s, 9H) 3.54-3.78 (m, 2H) 7.82 (br. s., 1H) 9.63 (br. s., 1H).