Substrate Inhibition in the Diels–Alder–Clar Reaction: Improved Synthesis of Benzoperylene Derivatives by Controlled Reaction Conditions

The sluggish Diels-Alder reaction of perylene with maleic anhydride is accelerated by the addition of chloranil as an oxidant to form the fully aromatic benzoperylene derivative using this Clar variant. However, only moderate yields were obtained even for a large excess of chloranil, whereas high yields could be obtained by means of stepwise addition; this behavior resembles the substrate inhibition of enzymes and is discussed in terms of aggregation. The improved synthetic method could be generalized for various perylene biscarboximides and even for systems with anellated heterocycles. The method allows for the first time a double extension of perylene itself to coronene derivatives in one step. This offers the possibility of a very short synthesis of coronene.