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Abstract
Treatment of ethyl oxalyl chloride or methyl oxalyl chloride with lithium diisopropyl(carboethoxyfluoromethyl)phosphonate[(i-PrO)2P(O)CFCO2Et]−Li+ 2 followed by in siru nucle-ophilic addition with methylmagnesium iodide or vinyl magnesium bromide affords with exclusive E-stereoselectivity formation of diethyl-2-fluoro-3-methyl fumarate (CH3)(C02Et)C[dbnd]CFCO2Et 4 or 75% of the E-isomer of a-fluoro-P-vinyl-a,P-unsaturated diester (E,Z)-(CH2[dbnd]CH)(CO2C2H5)C[dbnd]CFCO2Et 5, respectively. However, direct reaction of ethyl pyruvate with 2 gives the fluoro-olefin (CH3)(CO2Et)C[dbnd]CFCO2Et 4 with 79% E-stere-oselectivity. The E/Zratio of (CH2[dbnd]CH)(CO2Et)C[dbnd]CFCO2Et 5 depends on the HMFT or DMPU cosolvents present in the reaction mixture.