Oxalyl chloride → (S)-2-(3,4-dichlorophenyl)pent-4-enoyl chloride

Participants

Reaction Steps

Combine (S)-2-(3,4-dichlorophenyl)pent-4-enoic acid (6.55 g, 26.7 mmol), dichloromethane (10 mL), and dimethylformamide (2 drops). Add a solution of oxalyl chloride (16 mL, 2 M, 32 mmol) in dichloromethane. After 2 hours, evaporate in vacuo to give (S)-2-(3,4-dichlorophenyl)pent-4-enoyl chloride. Combine with toluene (20 mL) and slowly add, with vigorous stirring, to a cooled (ice bath) aqueous solution of methylamine (4 mL, 40%) while maintaining the temperature of the reaction mixture at less than 10° C. When the addition is complete add toluene (40 mL). After 1 hour, partition the reaction mixture between water and dichloromethane. Separate the layers, extract the organic layer with a saturated aqueous sodium bicarbonate solution, dry over MgSO4, filter, and evaporate in vacuo to give a residue. Chromatograph the residue on silica gel eluting sequentially with 10% ethyl acetate/hexane, 20% ethyl acetate/hexane, and 30% ethyl acetate/hexane to give (S)-2-(3,4-dichlorophenyl)pent-4-enoic acid, N-methyl amide: Rf=0.50 (silica gel, 50% ethyl acetate/hexane).

Provenance & Evidence