Study of all stages of the Diels–Alder reaction of cyclopentadiene with 2,3‐dicyano‐1,4‐benzoquinone and monoadducts: Kinetics, thermochemistry, and high pressure effect

Abstract

The kinetic parameters and enthalpies of the Diels–Alder reactions between cyclopentadiene and 2,3‐dicyano‐1,4‐benzoquinone leading to the formation of two different monoadducts and bisadduct were determined. The stability of adducts is compared. Monoadduct appears to be thermodynamically more stable than the bisadduct. Comparison with the other Diels–Alder reactions studied previously allows us to conclude that the heat effects upon formation of the considered Diels–Alder adducts are the lowest in comparison with all the studied dienophiles.

Sharp difference in the rate of formation and stability of the Diels–Alder reaction adducts with 2,3‐dicyano‐1,4‐benzoquinone and N‐phenylimide‐1,4‐benzoquinone‐2,3‐dicarboxylic acid

“…in the π, π‐complex with hexamethylbenzene in 1,2‐dichloroethane, dienophile 10 can be considered a stronger π‐acceptor ( λ max 575 nm, E c.t. 2.16 eV) 29 than 11 ( λ max = 530 nm, E c.t. 2.34 eV) and even than tetracyanoethylene ( 1 ) ( λ max = 538 nm, E c.t.…”

“…A known amount of solution of cyclopentadiene in 1,2‐dichloroethane, after equalizing the temperature in the calorimeter cell, was introduced into a solution of excess dienophile 11 . The heat of reaction 4 + 10 → 14 was determined earlier 29 . The heat of reaction 4 + 11 → 16 was determined twice.…”

Theoretical Studies on the Mechanism of the Formation of Cyclopentadienes and Dihydropyridazines

“…[1][2][3][4][5] Cps are well-known as precursors to build transition-metal complexes with Cp-type ligands in the field of coordination chemistry [6][7][8][9][10] and also as diene units to form cyclic heterocycles with the help of inter-and intramolecular Diels-Alder (DA) reactions. [11][12][13][14] Despite their importance, it is very difficult to synthesise substituted Cps, due to the instability of the parent Cp and the easy migration of the endocyclic double bonds. As a result, there is no straightforward method for the functionalisation of Cps.…”