engleski

Transfer Reagents IV : Retro Diels-Alder Routes to 3, 6-di(2-pyridyl)pyridazino norbornadiene, a Test Bed for the Relative Dienofugacity of Isobenzofurans, Isoindole and Anthracene

Norbornadiene cycloadducts have been reacted with 3, 6-di(2-pyridyl)-s-tetrazine to produce pyridazines 14, 16, 18 (diene protected alkenes), following dehydrogenation (DDQ) of the intermediate dihydropyridazines. The title 3, 6-di(2-pyridyl)-pyridazinonorbornadiene 3 was produced under flash vacuum pyrolysis conditions by ejection of anthracene from 14 (590 oC), isobenzofuran 16 (630 oC) or isoindole 18 (580 oC) establishing isoindole > anthracene > isobenzofuran dienofugacity order. Calculations of the respective retro Diels-alder activation energies at the B3LYP/6-31G* level of theory correctly predicted the experimentally found isobenzofuran> anthracene>isoindole order. Cavity bis-3, 6-di(2-pyridyl)-pyridazine (dppn) and chevron-shaped bis-dppn ligands were prepared from 3 by coupling at the norbornene pi-bond.

pyrolysis; cycloadditions; norbornenes; benzoxepine

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