Structures of Hemi-Curcuminoids in the Solid State and in Solution

Hemi-curcuminoids are derivatives of the antioxidant radical scavenger curcumin in which one styryl moiety is missing but the -diketone functionality is maintained. Five such derivatives have been prepared, and the X-ray molecular structures for all of them have been determined. The tautomerism of the five compounds has been studied by NMR in the solid state and in solution. An enol-enol proton transfer barrier has been determined.