PHOTOCHEMISTRY OF -4(3,4-METHYLENEDIOXYPHENYL)-4-OXO-2-BUTENONITRILE (BETA-CYANOCHALCONE) AND ITS RELATED-COMPOUNDS

Photochemistry of the titled compounds both in solid state and in solu tion is described. The (Z)-isomers of beta-substituted chalcones (5, 8 and 9) mainly dimerized into topochemically favored single cyclobutan e dimers (10, 14 and 13) in solid state photoreactions, while in solut ion those isomerized into the corresponding (E)-isomers. Interestingly exposure of the (E)-isomer (5E) of beta-cyanochalcone to sunlight in the solid state led to unusual dimerization through isomerization to g ive an unsymmetrical (E-Z)-dimer (11) along with a symmetrical (Z-Z)-d imer (10) obtainable from the photoreactive (Z)-isomer (5Z-b). The pho tochemical reactivities of the esters (9) are discussed based on their crystal structures.