Influence of the sulfinyl group on the chemoselectivity and pi-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 C-2-C-3 versus C-5-C-6 double bonds) is mainly related to the cyclic (on C-5-C-6) or acyclic (on C-2-C-3) structure of the diene. The high pi-facial selectivity observed could be controlled by choosing adequate experimental conditions.