摘要:
Treatment of ethyl oxalyl chloride or methyl oxalyl chloride with lithium diisopropyl(carboethoxyfluoromethyl)phosphonate [(i-PrO)(2)P(O)CFCO2Et]Li--(+) 2 followed by in situ nucleophilic addition with methylmagnesium iodide or vinyl magnesium bromide affords with exclusive E-stereoselectivity formation of diethyl-2-fluoro-3-methyl fumarate (CH3)(CO2Et)C=CFCO2Et 4 or 75% of the E-isomer of alpha-fluoro-beta-vinyl-alpha,beta-unsaturated diester (E,Z)-(CH2=CH)(CO2C2H5)C=CFCO2Et 5, respectively. However, direct reaction of ethyl pyruvate with 2 gives the fluoro-olefin (CH3)(CO2Et)C=CFCO2Et 4 with 79% E-stereoselectivity. The E/Z ratio of (CH2=CH)(CO2Et)C=CFCO2Et 5 depends on the HMPT or DMPU cosolvents present in the reaction mixture.