Maleimide cycloadditions by sulfinyldienes: is the sulfur configuration the only controller of the diastereofacial selectivity?

Cyclohexylsulfinyl-3-methyl-1,3-butadienes , , and 1-[1-(cyclohexylsulfinyl)ethenyl]cyclohexene (), easily prepared from cyclohexanethiol () via transient cyclohexanesulfenic acid (), were reacted with N-phenylmaleimide under different conditions, at normal and high pressure. The stereochemical outcome of these cycloadditions contributes a better understanding of the relationships among different factors controlling facial diastereoselection.