Structure proton sponges

Barth, T., Krieger, C., Neugebauer, RA. and Staab, H.A. (1991) 1,4,5,8-Tetrakis(dimethyla-mino)naphthalene synthesis, structure, proton sponge and electron donor properties. Ange-wandte Chemie — International Edition, 30, 1028-1030. 

Table 12 Structural details of the hydrogen bond in protonated proton sponges.

M. Pietrzak et al., Counteranion and solvent effects on scalar couplings and hydrogen bond structures of protonated sponges, to be published... 

This section covers primary, secondary, tertiary, and quaternary aminopyrazines (both nuclear and extranuclear) but not (functionally substituted amino)pyrazines such as hydrazino-, hydroxyamino-, or azidopyrazines. General discussions have appeared on the spectra of 2-pyrazinamine,255 257 991 the proton-sponge properties of 2,3,5,6-tetra(pyridin-2-yl)pyrazine in relation to its fine structure,925 the fluorescene properties of 3,6-diamino-2,5-pyrazinedicarboxylic acid derivatives in relation to their fine structures,1646,1659 the basic properties of aminopyrazines and other such azines in relation to their electronic structures,412,928 and the fine structures of 3-amino-2-pyrazinecarboxylic acid1340 and l,4-diacetyl-2,3-diphenylpiperazine.559... 

In one instance, the proton sponge derivatives 61 were prepared by nucleophilic displacement of the activated chlorine atoms in pen-dichloroacenaphthene 60 on heating with excess of dimethyl- or diethylamine (equation 2)53. Regrettably, the structure of all compounds reported in this work was elucidated without NMR analysis, utilizing only combustion analysis and IR spectroscopy. 

All known proton sponge analogues of this type contain /V-phenyl, /V-acyl, /V-amino or /V-niii oso groups. Though the majority of these compounds is not characterized by increased basicity, consideration of their structural and physicochemical features gives additional insight into the peri-interaction of the amino groups. 

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