Abstract
The cyclization of N-substituted 2-(2-aminoethyl)thiopseudoureas (AETs) to 2-aminothiazolines (2-Ats) was investigated. The AETs (I, II and III) having a substituent at the amino nitrogen afforded a simple 3-substituted 2-Ats. The phenyl derivative was cyclized easier than the corresponding methyl derivative. The AETs (VII and VIII) having a substituent at the nitrogen atom of the thiourea, however, afforded the mixture of products, IV (2-aminothiazoline) and a 2-(substituted-amino)-2-thiazoline. 2-Aminothiazoline (IV) was the main product in the case of methyl derivative (VII), while substituted 2-AT was the main product in the case of phenyl derivative (VIII). The AETs (XI and XII) in which the both nitrogens of thiourea were linked with two or three methylenes afforded 2-ATs (XII and XIV) without removal of an amine, and the free bases of these 2-ATs were unstable and underwent a rearrangement to give 2-(2-mercaptoethylamino)imidazoline or-tetrahydropyrimidine.
