Enolate salts of 4-fluoro-2-hydroxymethylene-3-oxobutyrates of formula wherein R1 is C1-10 alkyl, R2 and R3 are independently hydrogen or fluorine, M is an alkali or alkaline earth metal, and n is 1 or 2, are prepared from enolate salts of the corresponding 4-fluoro-3-oxobutyrates and carbon monoxide. The enolate salts of formula I can be alkylated or acylated to obtain the corresponding enol ethers and esters. The 4-fluoro-3-oxobutyrate starting material can be prepared from 1,1-difluoroethyl methyl ethers by SbF5-catalyzed fluoromethane elimination followed by halogen exchange with lithium chloride, reacting the thus obtained fluoroacetyl chloride with ketene and quenching with the appropriate alcohol R1—OH.