Photocycloaddition reaction of tropone and electron-accepting 9,10-dicyanoanthracene

摘要

The photoreaction of tropone 1 and electron-accepting 9,10-dicyanoanthracene (DCA) gave four products in less polar benzene while in more polar acetonitrile-dichloromethane (1 : 1) solution an [8 + 4]pi adduct was formed together with the above four products. The formation of the [8 + 4]pi adduct was enhanced by biphenyl and quenched by 1,4-dimethoxybenzene. According to Weller's equation, electron transfer from tropone 1 to DCA is estimated to be the endothermic (Delta G = +1.2 kcal mol(-1)). The following coupling reaction between DCA(.-) and 1(.+) to the [8+4]pi adduct, however, could make the electron-transfer process shift to generate the radical-ion pair. [References: 35]