NMR studies of benzoannulation in lithium, sodium and potassium ortho-formylphenolates

Lithium, sodium and potassium derivatives of (benzo)salicylaldehydes have been prepared and characterized by 1H and 13C NMR in order to see how the metal cation and benzoannulation affect spectral parameters. There is no qualitative effect of the alkali metal atom in the compounds studied (from this point of view salicylaldehydes remind β-diketones). On the other hand, 1H chemical shifts of the hydroxyl and formyl protons and 13C chemical shifts of C2 (bearing OX, X = H, Li, Na or K) and of that the formyl carbon show the most significant variations being the best indicators of aromatic character of the six-membered quasi-ring of salicylaldehyde. In contrast, C1 (bearing formyl moiety) is almost inert to the alkali cations but reflects nicely the position of benzoannulation.