Dihydrothiazine-thiazoline rearrangement reversibility of the process

Synthesis of new 2-amino-5-hydroxymethyl-2-thiazolines

“…However, these reactions are usually performed in polar media with heating, and from the reaction mixtures one isolates only five-membered thiazoline rings, because under these conditions there is an easy dihydrothiazine-thiazoline rearrangement [11]. There is published evidence for the reversibility of that rearrangement [12], so particular attention has been given to establishing the structures of the resulting hydroxyl derivatives.In order to choose the hydrolysis conditions, we examined the behavior of compounds 1a-h at various pH; according to [13] and our studies, these compounds are unstable in the presence of bases and may give rise to polymeric compounds of variable composition. Therefore, for the hydrolysis we examined the systems PbO-H 2 O or PbO-H 2 O-EtOH as appropriate to the solubility of the initial hydrogen halides of the 2-aminothiazolines 1a-h.…”

“…However, these reactions are usually performed in polar media with heating, and from the reaction mixtures one isolates only five-membered thiazoline rings, because under these conditions there is an easy dihydrothiazine-thiazoline rearrangement [11]. There is published evidence for the reversibility of that rearrangement [12], so particular attention has been given to establishing the structures of the resulting hydroxyl derivatives.…”