The Diels-Alder reactivity of various 2 H-thiopyrans bearing electron-donating substituents has been investigated. The approximate order of reactivity among the 2 H-thiopyrans studied was 4, 6-disubstituted 5-substituted> 4-substituted, 3, 5-disubstituted 3-substituted. Good yields of predominantly endo adducts are obtained with reactive dienophiles. With less reactive dienophiles, reactions are much slower and yields are attenuated due to the ...
