The structures of the anhydro-polymers of 2-aminobenzaldehyde

The anhydro-trimer formed from 2-aminobenzaldehyde on storage or, more rapidly, in dilute acid, is assigned the structure 2,4:2′,N-(o-aminobenzo)-1,3:α,2″-(α-hydroxytolueno)-1,2,3,4-tetrahydroquinazoline on the basis of ultraviolet, infrared, and nuclear magnetic resonance spectra. This replaces the previous formulation. The structure 1′,2′,3′,4′-tetrahydro-4′-hydroxyquinazolino[2′,3′-I]-1,12-dihydrotribenzo[b,f,j]-1,5,9-triazacycloduodecahexene dihydrochloride, is similarly assigned to the red anhydro-tetramer hydrochloride into which 2-aminobenzaldehyde is changed in concentrated acid, and 2,4:2′, N-(o-aminobenzo)-1,3:α,2″-[α-(o-formylanilino)tolueno]-1,2,3,4-tetrahydroquinazoline, to the pale yellow anhydro-tetramer formed when this salt is basified.The equilibria between these various polymers and the monomer are discussed. Quantitative data for the stability of 2-aminobenzaldehyde when stored are given for the first time.