Influence of the Sulfinyl Group on the Chemoselectivity and π-Facial Selectivity of Diels−Alder Reactions of (S)-2-(p-Tolylsulfinyl)-1,4-benzoquinone

Diels−Alder reactions of (S)-2-(p-tolylsulfinyl)-1,4-benzoquinone (1a) with cyclic (cyclopentadiene and cyclohexadiene) and acyclic dienes (1-[(trimethylsilyl)oxy]-1,3-butadiene and trans-piperylene) under different thermal and Lewis acid conditions are reported. Chemoselectivity (reactions on C₂−C₃ versus C₅−C₆ double bonds) is mainly related to the cyclic (on C₅−C₆) or acyclic (on C₂−C₃) structure of the diene. The high π-facial selectivity observed could be controlled by choosing adequate experimental conditions.