Diels-Alder Reaction

Diels-Alder Reaction

Diels-Alder Reaction

Diels-Alder Reactions are concerted, thermal [4+2] cycloadditions. It involves the 1,4-addition of an alkene(i.e.dienophile) to a conjugated diene to form a six membered-adduct. The reaction is initiated by heat, light or Lewis acid catalyst with or without the use of solvent. The reaction is usually thermodynamically favourable due to the conversion of two π-bonds into two new stronger σ-bonds. The Diels-Alder reaction is stereospecific with respect to both the diene and the dienophile.

Diels-Alder Reaction

Electron withdrawing groups in the dienophile or electron donating groups in the diene accelerates the rate of reaction and also the product is high yield.
Diels-Alder Reaction
When both the diene and dienophile are unsymmetrical, two products are possible. However 1,2- and 1,4-products predominates.
Diels-Alder Reaction

Mechanism of Diels-Alder Reaction

The possible mechanism is given below-
Diels-Alder reaction mechanism proceeds through the suprafacial (i.e. same-face involvement of the 𝝅 system or isolated orbital in the process) interaction between a 4𝝅 electron system with a 2𝝅 electron system.
Since the Diels-Alder reaction is a concerted process (i.e. both the bond formations and bond cleavages takes place simultaneously), so the reaction occurs in a single step cycloaddition reaction. The two unsaturated molecules (i.e. diene and dienophile) combine to form a cyclic adduct. Overall the bond multiplicity is reduced in this reaction.
Mechanism of  Diels-Alder Reaction
Diene reacts in the s-cis conformation, which allows the ends of the conjugated system to reach the doubly bonded carbons of the dienophile.
Mechanism of  Diels-Alder Reaction
There are two possible modes of addition i.e. exo and endo. The endo product is more stable.
Mechanism of  Diels-Alder Reaction

Applications of Diels-Alder Reaction

Applications of Diels-Alder Reaction

Applications of Diels-Alder Reaction