Retro hetero-Diels-Alder reaction
= Retro hetero-Diels-Alder reaction
A <retro hetero-Diels-Alder reaction> is the reverse of a <Diels-Alder reaction> involving a heteroatom-containing partner. For a six-membered ring with sequence $O-A-B=C-D-E$, cleavage of $O-A$ and $D-E$ can give $A=B-C=D$ and $E=O$. Whether the <cycloreversion> is concerted or proceeds through ionic intermediates depends on the substrate and conditions.