Retro‐Diels‐Alder Reaction

Abstract The thermally allowed [ π 4 s· + π 2 s ] cycloreversion of an organic compound with a double bond in a six‐membered ring, leading to the formation of a diene and a dienophile, i.e., the reversed process of the Diels–Alder cycloaddition. Thus this reaction is generally known as the retro ‐Diels–Alder fragmentation, or retro ‐Diels–Alder reaction. Even though the Diels‐Alder cycloaddition is thermodynamically reversible, the Diels‐Alder cycloaddition products are fairly stable, and the retro ‐Diels‐Alder reaction does not occur regularly. Besides the normal thermolysis of Diels‐Alder cycloadducts, a few conditions have also been reported to facilitate the retro ‐Diels‐Alder reaction. In addition, some special structural components may facilitate the retro ‐Diels‐Alder reaction too. It has been mentioned that the thermal retro ‐Diels‐Alder reaction of anthracene cycloadducts is accelerated by electron‐donating groups. This reaction has very wide application in organic synthesis, such as the formation of quinones, benzoquinones, heterocycle, etc.