Photochemical transformations. Part 10. Photocycloaddition reactions of 4-hydroxycoumarin with cycloalkenes

Abstract

Irradiation of 4-hydroxycoumarin in the presence of an excess of cyclohexene leads to the cyclobutane adduct, 6a,6b,7,8,9,10,10a,10b-octahydro-10b-hydroxybenzo[3,4]cyclobuta[1,2-c]chromen-6-one, in high yield. Analogous additions occur with cyclopentene, cycloheptene, cyclo-octene, norbòrnene, and 2,3-dimethylbut-2-ene. On treatment with triethylamine in methanol, the cyclohexene adduct is converted into methyl 2-o-hydroxybenzoylcyclohexylacetate and not the desired oxocin.