Ozone → [1-(Acetylaminomethyl)-2-methylcarbamoyl-2-oxoethyl]carbamic acid benzyl ester

Participants

Reaction Steps

A solution of [1-(acetylaminomethyl)-3-cyano-2-oxo-3-(triphenyl-λ5-phosphanylidene) propyl]carbamic acid benzyl ester (569.9 mg, 1.01 mmol, 1 equiv) in CH2Cl2 (11 mL) at −78° C. was treated with ozone gas for 3 h. The chilled solution was then purged with Ar for 30 min until the color had changed from green to yellow. DIEA (0.211 mL, 1.21 mmol, 1.2 equiv) and methylamine hydrochloride (75.1 mg, 1.11 mmol, 1.1 equiv) were added. After 1.5 h at −78° C., a second portion of DIEA (0.25 mL, 1.43 mmol, 1.4 equiv) and methylamine hydrochloride (80.0 mg, 1.18 mmol, 1.17 equiv) were added, and stirring continued at −78° C. for 2.5 h longer. The volatiles were removed under reduced pressure, and the residue was purified by flash column chromatography (5% CH3OH in CH2Cl2) to give [1-(acetylaminomethyl)-2-methylcarbamoyl-2-oxoethyl]carbamic acid benzyl ester (55.8 mg, 17% yield) as a pale yellow solid. Rf=0.23 (10% CH3OH in CH2Cl2). IR (cm−1) 3302, 1709, 1658, 1539. 1H NMR (CDCl3) (rotameric mixture) δ1.89, 1.95 (2 s, 3H), 2.77 and 2.89 (2 d, 3H, J =5.2), 3.47-3.54 (m, 1H), 3.61-3.69 (m, 1H), 4.29 (m, 1H), 5.10 (s, 2H), 6.64 (br s, 1H), 6.85 (br s, 1H), 7.06 (br s, 1H), 7.34 (s, 5H).

Provenance & Evidence