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 (Δ G ≈ 5.7–5.9 kcal/mol). Meanwhile, the domino products 6 are more thermodynamically stable than 5 (Δ G ≈ 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.