Abstract Mixtures of some (E)-and (Z)-2-fluoroalk-2-enoates prepared from the corresponding 2-hydroxycarbonyl compounds and ethyl 2-(diethoxyphosphoryl)-2- fluoroacetate have been transformed in high conversions into the target 3-fluorofuran-2 (5H)- ones by an efficient Z/E photoisomerisation of noncyclisable Z isomers followed by acid- catalysed cyclisation. In contrast, the acid-catalysed deprotection of ethyl (E)-and (Z)-4-[ ...