Abstract
Reaction of thiamine with diaryl carbodiimide was found to be quite different from that of the simple thiamine model compound giving unusual (1 : 2) adduct, S- [1- (2, 7-dimethyl-8-aryl-9-arylimino-5, 7, 8, 9-tetrahydroimidazo [1, 5-a] pyrimido [4, 5-d] pyrimidin-7-yl) -3-hydroxy-propyl] -N, N'-diaryl isothioureas (IIIa, IIIb). The structure of the (1 : 2) adduct was elucidated by chemical and spectroscopic evidences, and it was found that the (1 : 2) adduct (IIIa) underwent a novel acid-catalyzed decomposition reaction to give 7-methyl-2- (N-acetyl-N, N'-di-p-tolyl) amidino-1, 4-dihydropyrimido [4, 5-d] pyrimidine (VIIIa). Mechanistic consideration on these reactions was briefly made.
