Ethyl chloroformate → 4,4,4-Trifluoro-2-(triphenyl-lambda5-phosphanylidene)-butyric acid ethyl ester

Participants

Reaction Conditions

Reaction Steps

A suspension of (3,3,3-trifluoropropyl)triphenylphosphonium iodide (194.5 g, 0.4 moles) in tetrahydrofuran (THF—anhydrous, 800 mL) was cooled to −5° C. in an ice/brine bath under nitrogen. Lithium bis(trimethylsilyl)amide (1.0 M in THF, 800 mL, 0.8 moles) was added to this suspension drop-wise over 2 hours. The temperature was maintained below 5° C. throughout the addition. The reaction mixture was then cooled to −75° C. in a dry ice/acetone bath. To this solution, ethylchloroformate (76.5 mL, 0.8 moles) was added drop-wise over 30 minutes. The reaction was stirred at −75° C. for an additional hour and allowed to warm to 25° C. overnight. The reaction mixture was poured onto brine (1.5 L) and stirred for 30 minutes. The layers were separated and the organic layer was washed with brine (200 mL). The aqueous layer was washed with dichloromethane (CH2Cl2−2×200 mL) and the combined organics were concentrated to a residue. This residue was redissolved in CH2Cl2 (500 mL), dried over MgSO4, and filtered through a plug of magnasol. The solvent was reduced to a minimum (˜100 mL) in vacuo and the product was precipitated with hexanes (250 mL). The solvent was completely removed in vacuo and the solid product was triturated with hexanes (500 mL). The solid was isolated by filtration and dried overnight in vacuo at 25° C. to give a beige powder 152.8 g, 89%).

Provenance & Evidence