[s30.93a]

Diels Alder reaction with contorted conformation

[Enthalpy]

Are hydrogen atoms expected to move? If not, the double bond is at the wrong place in the product.

[s30.93a]

yes double bond will be at bridge head

[kriggy]

Wouldnt the double bond at bridgehead violoate the bredts rule?

[s30.93a]

indeed, but we can draw it as a pie bond in 7 membered ring and that pie bond (say at C1) is connected to C4 via -CH₂-CH₂-

[Enthalpy]

Wouldn't the double bond at bridgehead violate Bredt's rule?

Oops. I've tried to run Am1 on the hypothetical product and it looks indeed strained despite the longer bridge.
So what? No reaction at all? Rearrangement? Single cycle retaining two double bonds?

[Enthalpy]

If we were to believe Am1, the Diels-Alder product would have a heat of formation of -7kcal/mol and the reactant +5kcal/mol, so from that criterion, Bredt's rule wouldn't apply so clearly with a 3-membered bridge.

Am1 isn't too wrong on butadiene's heat of formation. But to proceed, Diels-Alder would need an improbable conformation of the reactant.

Comments?