Diels-Alder Reaction (with Retro version)

The Diels-Alder reaction is a [4+2] cycloaddition in which a conjugated diene, called the diene, reacts with an alkene group or an alkyne group in a compound, called the dienophile, to give a cycloadduct, called the Diels-Alder adduct.

eg. 1:

eg. 2:

mechanism:  The Diels-Alder reaction is a pericyclic reaction.

Retro Diels-Alder Reaction

The Diels-Alder reaction is reversible.  The equilibrium lies by far toward the Diels-Alder adduct at lower temperature and, at higher temperature, toward the diene and the dienophile.

eg:

If a Diels-Alder adduct is heated at a much higher temperature than the temperature at which it forms in a Diels-Alder reaction, it breaks down to give the diene and the dienophile.  The reaction, which is a cycloreversion, is called the retro Diels-Alder Reaction.

mechanism:  Retro Diels-Alder reaction is a pericyclic reaction.