Terminal allenes linked to cyclohexenones by hydrocarbon chains were synthesized &nd irradiated with UV light. It was found that [2+ 21 cycloaddition occurs regiospecifically in high yield. The adducts were oxidized by ozone to 1, 3-diketones which underwent cleavage to the corresponding keto acids.
![2-(1,4-dioxaspiro[4.5]decan-6-yl)propyl methanesulfonate结构式](https://image.chemsrc.com/caspic/249/82026-18-4.png)
![6-(3-iodopropyl)-1,4-dioxaspiro[4.5]decane结构式](https://image.chemsrc.com/caspic/211/82026-19-5.png)