Zur Kenntnis der Struktur der Chalkon-Guanidin-Kondensate Über Heterocyclen, 75. Mitt.

Guanidine reacts with chalkone1 a, 4-methylchalkone1 b and 4′-methylchalkone1 c resp. to yield mixtures of pyrimidinamines2 a,3 b and3 c (=3 b) resp. with (2:1)-condensatesA,B andC resp. The structures of the compoundsA-C (whicha priori could be dihydropyrimidopyrimidines4 a-c or5 a-c or6 a-c) are elucidated. NMR-investigations show that the saltsA-C · HCl must be symmetrically substituted pyrimidopyrimidinyliumchlorides4 a-c · HCl or5 a-c · HCl (and not6 a-c · HCl). Furthermore, it is proved by chemical methods that the condensatesB · HCl andC · HCl are pyrimidopyrimidinyliumchlorides4 b andc · HCl (and not5 b andc · HCl): The structure ofB · HCl (=4 b · HCl) was established by total synthesis of dimethylpyrimidopyrimidinyliumpicrate9 b-Pi from10 c (via13 c · HI-18 · HCl) and transformation ofB · HCl into an identical salt9 b-Pi via hexahydropyrimidopyrimidine8 b · HCl. The structure ofC · HCl (=4 c · HCl) was determined by comparison of its hydrogenation product (=8c · HCl) with8 b · HCl. The structure of condensateA · HCl (=4 a · HCl) results from conclusion by analogy. The spatial structure of4 a-c · HCl and8 a-c · HCl is discussed; it was established by NMR that the salts are racemic mixtures of stereoisomers4 a-c K · HCl and8 a-c K · HCl resp. and their antipodes (with C₂ symmetry).