Fig. 7: DFT calculations.

DFT calculations of lowest energy structures of 4,5- and 1,4-dihydropyridazine tautomer products derived from 2a and 2b with TCO 9. DFT calculations demonstrate hydrogen bonding in 25a that is postulated to lead to 4,5-1,4 dihydropyridazine tautomerization and subsequent out-of-plane rotation of the top ring in 25b, while this is not observed for 19a and 19b.