Diels–Alder Reactions with Ethylene and Superelectrophiles

Abstract

Diels-Alder reactions have been accomplished with ethylene as the dienophile through the use of inverse-electron demand Diels-Alder chemistry. As a key aspect of the chemistry, the dienes are part of tri- or dicationic superelectrophilic systems. Theoretical calculations reveal that the highly charged superelectrophiles possess exceptionally low lying LUMOs, and this facilitates the cycloaddition chemistry with ethylene. The chemistry has been used to prepare a series of tetrahydroquinoline products. This represents the first application of superelectrophilic activation in a cycloaddition reaction, and a new method of utilizing ethylene as a C building block.

Acetylene and Ethylene: Universal C2 Molecular Units in Cycloaddition Reactions

“…In works from 2018/2019, inverse electron demand Diels–Alder reactions between ethylene and di- or tricationic superelectrophilic systems as dienes were performed. 5c d Superelectrophiles 186 were generated in situ from N -arylimines 185 in the presence of the Brønsted superacid triflic acid and smoothly added to ethylene under mild conditions to afford heteroaryl-substituted tetrahydroquinolines 187 in good yields (Scheme 84a ). Theoretical calculations reveal that highly charged superelectrophiles possess exceptionally low LUMO levels, which significantly lowers the activation energy for cycloaddition with ethylene and facilitates these reactions.…”

“…Theoretical calculations reveal that highly charged superelectrophiles possess exceptionally low LUMO levels, which significantly lowers the activation energy for cycloaddition with ethylene and facilitates these reactions. 5d The cycloaddition may be accomplished with subsequent oxidation with elemental sulfur to afford heterocyclic biaryl products 188 (Scheme 84b ). 5c…”

Superelectrophiles: Recent Advances

“…In addition to electrocyclizations, we have recently described the first superelectrophilic cycloaddition [ 71 ]. It is known that superelectrophiles often exhibit distorted molecular orbitals, including very low energy LUMOs and high coefficients at atomic centers—characteristics that could be useful in cycloaddition reactions [ 3 ].…”

Temperature‐Dependent Diels‐Alder Cycloaddition on Polyoxometalate‐Supported Single‐Atom Catalysts M1/PTA (M=Mn, Fe, Co, Ru, Rh, Pd, Os, Ir and Pt; PTA=[PW1240]3−)

“…[2] Therefore, this reaction gives a simple and general entry for the synthesis of a multitude of six-membered cyclic structures. [3] This reaction proceeds rapidly, in good yield with high stereoselectively simultaneously. Over the last few decades, the mechanisms, energetics, structures and transition state properties of DÀ A reaction have been investigated extensively by numerous experimental and computational studies.…”