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When 1,3-butadiene and dienophiles react with a Diels-Alder
mechanism, the reactivity is low and usually requires prolonged heating above
100 °C. Consequently, if neat butadiene is used, special equipment for work
under elevated pressure is also required making the whole procedure rather
dangerous. Sulfolene can be used as an alternative to generate butadiene in
situ by thermal sulfur dioxide extrusion. In this case we don’t expect buildup of
butadiene pressure as the released diene is consumed in the cycloaddition, and
therefore the equilibrium of the reversible extrusion reaction acts as an
internal “safety valve”. This is the practical advantage of the use of
3-sulfolene as the source of 1,3-butadiene provide over directly using
1,3-butadiene during a diels-alder experiment
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