(2+4)-Cycloaddition with Singlet Oxygen. 17O-lnvestigation of the Reactivity of Furfuryl Alcohol Endoperoxide¶

In earlier work, the use of furfuryl alcohol as a specific singlet oxygen acceptor was proposed because of the high ratio between the rate constants of chemical reaction and physical quenching. In contrast to furfuryl aldehyde, a number of products are formed by this type II photo-oxidation of furfuryl alcohol. These products may be derived from the endoperoxide of furfuryl alcohol as a common intermediate. The present work focuses on the reactivity of this endoperoxide that was marked specifically by the use of ¹⁷O₂ as a source for singlet oxygen. The analyses of the stable products, their yields and their labeling distribution reveal a strong solvent effect on the primary reaction pathways, and nucleophilic substitution reactions leading to hydroperoxide intermediates are dominant.