Iminophosphorane-substituted proton sponges. Part 4. Comparison of X-ray molecular structures with solution properties (pKa, 1H and 13C NMR spectroscopy)

Abstract

Classical ‘proton sponges’ related to 1,8-bis(dimethylamino) naphthalene (DMAN) and new ones derived from the replacement of one or both dimethylamino groups by iminophosphorane groups are compared (i) in the solid state using crystallographic data, (ii) in solution in deuteriochloroform and [²H₆]dimethyl sulfoxide by ¹H and ¹³C NMR spectroscopy, (iii) in water and ethanol–water mixtures by determining their pK_a′ s. The conclusion is that the new sponges are stronger than the classical ones but, since they decompose when the acid proton is removed are of no practical value as chemical reagents.