Electronic structure and spectral characteristics of trinaphthodifuryls

Quantum-chemical interpretation of cyclization and recyclization reactions. 27. Electrocyclization of phenyl derivatives and benzoannelated derivatives of 1,2,4-triazahexa-1,3,5-triene and 1,2,4-oxadiazahexa-1,3,5-triene

“…Thus from a comparison of the charge on the carbon atom of the imine group in compounds 14 (q 5 = 0.183), 15 (q 5 = 0.200), 16 (q 5 = 0.155), 17 (q 5 = 0.170), 18 (q 5 = 0.176) with the charges on the methylene groups of the anhydrobases [23. 24] (q = -0.18 to -0.27) and dienols [25,26] (q = −0.09 to -0.13) it is possible to draw the conclusion that the latter possess substantially less C-H acidity than the 4-alkyl analogs of azoimines 1b, 1e. Consequently the azoimine-ylideneimidrazone and nitrosoimine-ylideneoxime equilibria (Scheme 4) must be displaced strongly to the right (the more so the greater the residual π-electron charge on the CH 2 fragment), which was also observed experimentally [6-9, 12, 13].…”

“…We stress that with the parametrization used previously electrical, diamagnetic, and spectral characteristics have been calculated for a series of five-and six-membered heterocycles (see for example [20]), thermal rearrangements have been described for a series of annelated hexatrienes and polyenes [21,22], a quantum-chemical interpretation has been given for the Kost-Sagitullin [23,24] and Elbs [25,26] reactions, etc.…”