tert-Butyl 2-(methoxy(methyl)amino)-1-methyl-2-oxoethylcarbamate → (1-Methyl-2-oxo-2-phenyl-ethyl)-carbamic acid tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

tert-butyl 1-(N-methoxy-N-methylcarbamoyl)ethylcarbamate (39) (2.3 g, 10.0 mmol, 1.0 equiv.) was added to a 250 mL RBF followed by THF (100 mL). The mixture was cooled to 0° C. via an ice bath and a 1.0 M solution of PhMgBr in THF (30.0 mL, 30.0 mmol, 3.0 equiv.) was added over 8 min. The reaction stirred for 1.0 h at 0° C. and the ice bath was removed. The reaction stirred for an additional 1.0 h at rt. and was again cooled to 0° C. via an ice bath. Next, the reaction was quenched by addition of 1.0 M HCl (60 mL). The solution was transferred to a separatory funnel with additional 1.0 M HCl (40 mL) and extracted with EtOAc (3×75 mL). The organic layers were combined, washed with sat. NaCl (1×50 mL), and dried over Na2SO4. The solution was then concentrated on a rotary evaporator and dried under vacuum to give 3.1 g of crude material. The residue was purified by flash column chromatography (15% EtOAc/Hexanes) to give 2.2 g (86%) of 40 as a colorless oil.10 Rf=0.25 (15% EtOAc/Hexanes); IR (film) 3356, 2977, 1680, 1164 cm−1; 1H NMR (500 MHz, CDCl3) δ 7.96 (d, J=7.5 Hz, 2H, Ph-H), 7.59 (t, J=7.5 Hz, 1H, Ph-H), 7.48 (t, J=7.5 Hz, 2H, Ph-H), 5.62 (br d, J=6.5 Hz, 1H, carbamate-NH), 5.30 (t, 1H, Boc-NH—CH), 3.78 (s, 3H, N—OCH3), 3.19 (s, 3H, N—CH3), 1.46 (s, 9H, Boc-t-butyl-CH3, 1.40 (d, J=7.0 Hz, 3H, CH—CH3); 13C NMR (125 MHz, CDCl3) δ 199.6, 155.5, 134.3, 133.9, 129.0, 128.8, 80.0, 51.3, 28.6, 20.1; LRMS (ESI-MS m/z): Mass calcd for C14H19NO3 [2M]+, 498.62. Found 499. Spectroscopic data were consistent with the literature data for this compound.

Provenance & Evidence