Reaction of Salicyl N-Tosylimines with 2-Cyclohexenone: A Facile Access to Tetrahydroxanthenones

The reactions of salicyl N-tosylimines with 2-cyclohexenone can be carried out under mild reaction conditions in the presence of PPhMe2 (25 mol%), which provided a facile access to tetrahydroxanthenones within a few hours in most cases. In the reactions of salicyl N-tosylimines with 2-cyclopentenone, either the corresponding aza-Baylis-Hillman products or the corresponding cyclized products, or the mixtures of the two products, were obtained in moderate to good yields under the similar conditions depending on the salicyl N-tosylimines. A plausible reaction mechanism is discussed.