The photochemistry of 1-(3,5-dimethoxyphenyl)-2-(4-methoxyphenyl)ethyl ethanoate in alcohol solvents: A search for carbocation rearrangements

The photochemistry of the title compound 1 in methanol and 2,2,2-trifluoroethanol has been examined. In both solvents two ether products were obtained: one (18) resulting from trapping of the carbocation 2 (expected from photosolvolysis of 1), and the other (19) from the carbocation 3 (expected after rearrangement by hydride migration of cation 2). The substituted trans- and cis-stilbene derivatives 20 and 21 were also primary photoproducts. Analysis of product yields as a function of time revealed that the ether product 19 was formed by secondary photolysis of the stilbene derivatives, presumably by a pathway involving excited state protonation. Nanosecond laser flash photolysis results demonstrated that substituted trans-stilbene 20 was produced on the same time scale as the laser pulse.