Photochemically Induced Solid State Dimerisation of Resveratrol Analogues: A Greener Synthetic Process*

The photochemical dimerisation of resveratrol analogues in the solid state to generate chiral phenyl substituted cyclobutanes is described. NMR spectroscopic and X-ray crystallographic methods have confirmed that the dimerisation leads to the head to tail orientation of the phenyl group substituents in the cyclobutane derivative. Interestingly, the parent compound, resveratrol, in the solid state, did not form a cyclobutane dimer, but the O-acetyl analogues gave the corresponding cyclobutane dimers in high yield, suggesting that the close packing of molecules together with the electron density through the conjugated double bond of the resveratrol structure are important determinants for photodimerisation to occur in the solid state.