The UV irradiation of 1-cyclopentenyl phenethyl ketone in benzene or methanol gave a cyclobutane derivative. The irradiation of 1-cyclohexenyl phenethyl ketone in methanol or in benzene containing either BF 3–Et 2 O or CF 3 COOH gave a cycloheptanone derivative. The formation of the cycloheptanone derivative requires an acid catalyst.
![1-phenylspiro[3.4]octan-3-one Structure](https://image.chemsrc.com/caspic/257/65923-47-9.png)