Captodative olefins in normal and inverseDiels‐AlderReactions

Abstract

AbstractOlefins with captodative substitution are reactive dienophiles inDiels‐Alderreactions with normal and inverse electron demand. This is shown for reactions of 2‐(tert‐butylthio)acrylonitrile (1) with various dienes and heterodienes,e.g.1,3‐cyclohexadiene, hexachloro‐1, 3‐cyclopentadiene, acrolein, methacrolein, and methyl vinyl ketone (Schemes 2and3). In case of the hetrodienes, 3,4‐dihydro‐2H‐pyrans are formed beside small amounts of tetrahydrothiophenes; however, with methyl vinyl ketone, both reaction pathways are equally followed. The high reactivity of captodative olefins inDiels‐Alderreactions are rationalized on the basis ofSustmann's FMO model under consideration of Viehe's concept of captodative substitution of alkenes.