Reaction Scheme
conjugated diene + dienophile -> cyclohexene derivativeThermal reaction; electron-rich dienes and electron-poor dienophiles are common.
Primary reaction SMILES: C=CC=C.C=CC=O>>O=CC1C=CCCC1
Organic reaction
Diels-Alder Reaction
The Diels-Alder reaction is a concerted [4+2] cycloaddition between a conjugated diene and a dienophile, forming cyclohexene frameworks with predictable stereochemical outcomes.
Two Common Examples
Butadiene + ethene
Classic teaching example forming cyclohexene.
Cyclopentadiene + maleic anhydride
Common lab example showing endo selectivity.
MolDraw Use
Use MolDraw to show diene geometry, dienophile substituents, stereochemistry, and cycloaddition products.
How It Works
The Diels–Alder reaction is a concerted [4+2] cycloaddition between a conjugated diene and a dienophile (an alkene or alkyne). Six π electrons reorganise in a single step through a cyclic transition state, forming two new C–C σ bonds and a cyclohexene ring. No intermediate is formed, which is why the stereochemistry of the dienophile is kept in the product: a cis dienophile gives cis substituents on the ring.
Conditions and Scope
- The diene must be able to adopt the s-cis conformation. Cyclopentadiene is locked s-cis and is very reactive.
- Electron-withdrawing groups on the dienophile (C=O, CN, CO2R) and electron-donating groups on the diene speed up the normal-demand reaction.
- With cyclic dienes, the endo product is usually favoured under kinetic control (the endo rule).
- Lewis acids can accelerate the reaction and raise selectivity.
FAQ
How do I draw it clearly? Number the diene carbons 1–4 and draw three curved arrows around the ring to show the concerted electron flow. Use wedge and hash bonds on the product to show endo/exo stereochemistry. What is a retro-Diels–Alder? The reverse reaction on heating, used for example to crack dicyclopentadiene back to cyclopentadiene.