The photochemical isomerization 2-furylidenetetralone

A DFT study on the photochemical isomerization of furylidenetetralone derivatives is reported. The excitation of the trans isomer of the starting material can give the cis one, converts the S1 into the corresponding triplet state, or can be converted directly into the transposed product. The excitation of the cis isomer of the starting material can give the same triplet state observed with the trans isomer; however it cannot be converted into the transposed product because the energy of the transition state is too high. Finally, compounds with the structure Het CH=CH-COPh can give a sensitized dimerization reaction, never observed in this case. The calculations showed that, while with compounds such HetCH=CH-COAr the biradical intermediate of the dimerization reaction was obtained in very fast exothermic reaction, in the case of the furylidenetetralone derivative, the formation of the dimeric biradical intermediate is highly endothermic and, than, less probable.