The singlet oxygen ene reactions of four allylic alcohols and for comparison an allylic ether have been examined both in solution and in zeolite Y. Brønsted acid sites in the zeolite were shown to induce decomposition of several of the allylic alcohols. Treatment of the zeolites with pyridine removed these acid sites and allowed intrazeolite reactions of the allylic alcohols without interference from decomposition. Control reactions with an allylic alcohol that is inert to decomposition provided evidence that the presence of pyridine in the zeolite labyrinth does not influence the product composition.