What Are Diels-Alder Reaction?

The Diels-Alder reaction (DA) is a [4+2] cycloaddition reaction of conjugated diene and dienophile. Since its discovery1, it has been recognized one of the keystone methods in organic synthesis for the formation of six membered rings.2 It has break new ground in the construction of many complex organic molecules.3 Fig. 1
The utility of the DA reaction has been further expanded by the incorporation of heteroatoms in both the diene and dienophile and are known as hetero-Diels-Alder (HDA) reaction.4
The HDA reaction is one of the most used synthetic strategies for the construction of six membered heterocyclic compounds5 having specific nature for example drugs or natural products.6
Various heteroatoms are capable HDA reaction, the most common being oxygen, nitrogen and sulphur. Here the emphasis will be on oxa-cycloaddition reaction. …show more content…
dihydropyran accessible, which occurs as structural pattern in many biologically active natural products.7
Hetero-Diels-Alder reactions of carbonyl compound can be classified into two types of [π2s+ π4s] cycloadditions, the normal and inverse electron demand cycloadditions (Fig. 2) based on the relative frontier molecular orbitals (FMOs) energies of diene and