Abstract: The Diels-Alder reaction of thioaldehydes with cyclopentadiene occurs with a preference for the endo isomer. The highest selectivity is observed for thioaldehydes RCHS where R is a bulky alkyl group such as tert-butyl or isopropyl. Thioaldehydes having a- alkoxy, acetoxy, or doxy substituents also react with useful endo selectivity. Secondary orbital overlap is a small factor in these reactions since a-oxo thioaldehydes react with ...
