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Synthesis of the Guanidium-Meldrum acid zwitterionic salts was developed through a three component reaction of 2, 2-dimethyl-1, 3-dioxane-4, 6-dione (Meldrum acid), aromatic aldehydes and N, N, N’, N’-Tetramethyl-guanidine in benzen at room temperature. These reaction conditions allow the preparation of stable zwitterionic salts in good yields. A dynamic NMR effect is observed as a result of restricted rotation around the C-NH bond in the 1H NMR spectra of these compounds. The free-energy of activation (G # ) for this process is 66 ± 2 kJmol -1 for 4b.

Synthesis of new Guanidium-Meldrum acid zwitterionic salts and dynamic NMR study of rotational energy barrier around C-NH bond of guanidine moiety