Thioacylketene thioacetal

An interesting and reactive class of 4ir thiabutadienes capable of useful participation in normal (HOMOdiene controlled) Diels-Alder reactions are the stable thioacylketene thioacetals,22 generated by the photoaddition of olefins to l,2-dithiole-3-thiones23 [Eq. (10)]. 

Olefinic, acetylenic, and typical electron-deficient dienophiles participate in apparent concerted [4 + 2] cycloadditions with the thioacylketene thioacetals (Scheme 8-V), while enamines provide modest yields of [4 + 2] cycloadducts via a polar, stepwise addition-cyclization.22c... 

Analogous thioacylketene thioacetals have been reported to give a [4 + 2] adduct with sulfene (equation 103) under similar reaction conditions209. 

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