1,2-Dichloroethane → [1-(Acetylaminomethyl)-3-cyano-2-oxo-3-(triphenyl-lambda5-phosphanylidene) propyl]carbamic acid benzyl ester

Participants

Reaction Conditions

Reaction Steps

This intermediate was prepared generally according to the method of Wasserman et al., J. Org. Chem. (1994), vol. 59, 4364. In particular, to a solution of (3-acetylamino-2-benzyloxycarbonylaminopropionic acid (1.40 g, 5.0 mmol, 1 equiv) in CH2Cl2 (50 mL) at 0° C. were added EDC (1.00 g, 5.25 mmol, 1.05 equiv) and DMAP (61 mg, 0.5 mmol, 0.1 equiv). A solution of (cyanomethylene)triphenylphosphorane (prepared as described in Freudenreich et al., J. Am. Chem. Soc. (1984), vol. 106, 3344) (2.50 g, 8.30 mmol, 1.66 equiv) in CH2Cl2 (16 mL) was added to the acid solution dropwise over 20 min. After stirring 2 h at 0° C., the reaction mixture was partitioned between deionized water (30 mL) and CH2Cl2 (3×50 mL). The combined organic layers were washed with brine (30 mL), dried over MgSO4, filtered, and concentrated. The residue was purified by flash column chromatography (5% CH3OH in CH2Cl2) to give [1-(acetylaminomethyl)-3-cyano-2-oxo-3-(triphenyl-λ5-phosphanylidene)propyl]-carbamic acid benzyl ester (1.98 g, 70% yield) as a colorless foam. Rf=0.40 (10% CH3OH in CH2Cl2). IR (cm−1) 3312, 2175, 1716, 1437. 1H NMR (CDCl3) δ1.91 (s, 3H), 3.66-3.79 (m, 2H), 5.04-5.06 (m, 1H), 5.10 (s, 2H), 5.94 (br s, 1H), 6.21 (br s, 1H), 7.26-7.70 (m, 21H).

Provenance & Evidence