The sodium salt of 3-(hydroxymethylene)dihydro-2(3H)-furanone (I) can be obtained in solid state in the form of (Z)-isomer, or their mixture, whereas in solutions it only exists in the form of (E)-isomer. Reactions of these sodium salts with sulphonyl or acyl chlorides or sulphonic acid anhydrides give the respective (E)- and (Z)-sulphonates or carboxylates of 3-(hydroxymethylene)dihydro-2(3H)-furanone in high yields and purity. Configuration of the sodium salt isomers has been confirmed by their IR and 12C NMR spectra in solid state, that of the isomeric sulphonates and carboxylates has been confirmed by their 1H and 13C NMR spectra in solution.
Solid state photodimerization in an organic salt of 1,2-bis(4-pyridyl)ethylene and trifluoromethane sulphonic acid via pedal-like motion