tert-Butyl carbamate → tert-Butyl (2E)-but-2-enoylcarbamate

Participants

Reaction Steps

To a solution of tert-butyl carbamate (1.0 g, 8.54 mmol) in THF (20 mL) at −78° C., were added nBuLi and 2-butenoyl chloride successively, in the following quantities (nBuLi/2-butenoyl chloride): 5.34/0.41, 2.67/0.21, 1.34/0.10, 0.67/0.05, 0.34/0.03 mL. Stirring was continued for 30 min, before the reaction mixture was poured into an ice-cooled solution of saturated aq. NaHCO3 (50 mL) and extracted with EtOAc. The combined organic layers were washed with brine, dried over MgSO4, and evaporated. The crude product was purified by flash chromatography (Et2O:pet. ether, 1:3, Rf 0.4) to give the product as a white solid. Yield 81% (1.28 g). m.pt. 138–139° C. 1H NMR: δ 1.49 (s, 9H, tBu); 1.92 (dd, 1H, CH3CH, 2JHH=6.8 Hz, 3JHH=1.5 Hz); 6.82 (dd, 1H, COCH, 2JHH=15.2 Hz, 3JHH=1.5 Hz); 7.05–7.15 (m, 1H, CH3CH); 7.31 (s, br, 1H, NH). 13C NMR: δ 15.9 (CH3CH), 27.9 (C(CH3)3), 82.3 (C(CH3)3), 121.2 (COCH), 145.5 (CH3CH), 150.5(CO2), 166.3 (COCH). m/z (HR-ESMS): Expected 185.1052 (M+), observed 185.1046. Anal. calcd for C9H15NO3: C, 58.36; H, 8.16; N, 7.56%. Found: C, 58.08; H, 8.05; N, 7.63%.

Provenance & Evidence