FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY OF NEW POLYDENTATE SCHIFF-BASES .5. THE CASE OF BIS-ALDIMINES CONTAINING OXAMIDE GROUPS

Four macrocyclic tetraimine Schiff bases containing oxamidic groups we re synthesized by [2+2] condensation of N,N'-bis(2- aminoethyl)oxamide or N,N'-bis(2-amino-1,1-dimethylethyl)oxamide with 2,6-diformyl-4-chl orophenol or 2,6-diformyl-4-methylphenol and characterized by elementa l analyses and IR and NMR spectrometry; their [2+2] cyclic nature was inferred (especially) by fast-atom bombardment (FAB) mass spectrometry . The FAB-induced fragmentation patterns of the protonated molecules, investigated with the aid of metastable ion studies, evidence characte ristic behaviours related to the presence of oxamidic groups or of 1,1 -dimethylethyl species. (C) 1997 by John Wiley & Sons, Ltd.