2-α-Hydroxyalkyl- and 2,7-Di(α-hydroxyalkyl)-1,8-bis(dimethylamino)naphthalenes: Stabilization of Nonconventional In/Out Conformers of “Proton Sponges” via N···H−O Intramolecular Hydrogen Bonding. A Remarkable Kind of Tandem Nitrogen Inversion

A regular set of 2-(α-hydroxymethyl)- and 2,7-di(α-hydroxymethyl)-1,8-bis(dimethylamino)naphthalenes has been prepared. Their X-ray, NMR, and IR studies have demonstrated that in tertiary mono-alcohols the orientation of free nitrogen electron pairs in crystals and solution corresponds to nonconventional in/out conformers stabilized by O−H···N intramolecular hydrogen bonding. For tertiary 2,7-dialcohols, the superimposed equilibrating in/out−out/in nitrogen invertomers are observed in solution. Unlike this, primary and secondary mono- and dialcohols commonly exist in the in/in form, which is typical for the parent proton sponge and the majority of its derivatives.