Diels Alder if dienophile does not have electron-withdrawing group?

[questioneverything3.14]

Does the dienophile have to have an electron-withdrawing group for the diels-alder reaction to occur? I know the electron-withdrawing group causes the partial positive charge, but if the dienophile was just ethene, could the diels-alder reaction still occur with just heat?

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[theonlytycrane]

Yes, but EWG make the dienophile more electrophilic for attack.

Diels-Alder isn't on the MCAT, btw.

 

[aldol16]

What's not usually taught is that the "classic" Diels-Alder reaction of ethylene and 1,3-butadiene doesn't actually work - you need a substituted olefin. But that substituent doesn't have to be electron-withdrawing - you also have so-called inverse electron demand Diels-Alder reactions where the substituent is actually electron-donating.

 

[theonlytycrane]

@aldol16 oh really? Is the reaction with ethylene low-yield in practice?

 

[aldol16]

@aldol16 oh really? Is the reaction with ethylene low-yield in practice?

It's exceedingly slow and only works when you heat it up and pressurize the reaction vessel.

 

[questioneverything3.14]

That's amazing, thanks guys!

@aldol16 oh really? Is the reaction with ethylene low-yield in practice?

It's exceedingly slow and only works when you heat it up and pressurize the reaction vessel.