text: The Diels–Alder reaction of cyclopentadiene with furan can produce two isomeric products. At room temperature, kinetic reaction control prevails and the less stable endo isomer 2 is the main reaction product. At 81 °C and after long reaction times, the chemical equilibrium can assert itself and the thermodynamically more stable exo isomer 1 is formed. The exo product is more stable by virtue of a lower degree of steric congestion, while the endo product is favoured by orbital overlap in the transition state. 
  An outstanding and very rare example of the full kinetic and thermodynamic reaction control in the process of the tandem inter-/intramolecular Diels–Alder reaction of bis-furyl dienes 3 with hexafluoro-2-butyne or dimethyl acetylenedicarboxylate (DMAD) have been discovered and described in 2018. At low temperature, the reactions occur chemoselectively leading exclusively to adducts of pincer-[4+2] cycloaddition (5). The exclusive formation of domino-adducts (6) is observed at elevated temperatures.
  Theoretical DFT calculations of the reaction between hexafluoro-2-butyne and dienes 3a-c were performed. The reaction starting with [4+2] cycloaddition of CFC≡CCF at one of the furan moieties occurs in a concerted fashion via TS1 and represents the rate limiting step of the whole process with the activation barrier ΔG≈ 23.1–26.8 kcal/mol.
  Further, the reaction could proceed via two competing channels, i.e. either leading to the pincer type products 5 via TS2k or resulting in the formation of the domino product 6 via TS2t. The calculations showed that the first channel is more kinetically favourable (ΔG≈ 5.7–5.9 kcal/mol). Meanwhile, the domino products 6 are more thermodynamically stable than 5  (ΔG≈ 4.2-4.7 kcal/mol) and this fact may cause isomerization of 5 into 6 at elevated temperature. Indeed, the calculated activation barriers for the 5 → 6 isomerization via the retro-Diels–Alder reaction of 5 followed by the intramolecular [4+2]-cycloaddition in the chain intermediate 4 to give 6 are 34.0–34.4 kcal/mol.