Structure of 2-amino-4-thiazolinone and its 2-aryl derivatives in the crystalline state

Proton tautomerism and stereoisomerism in 5-[(dimethylamino)methylidene]-4-[3/4-(trifluoromethylphenyl)amino]-1,3-thiazol-2(5H)-ones: synthesis, crystal structure and spectroscopic studies

“…It is worth noting that the amine tautomer is also present, at least in the solid phase, in the isomeric 5-[(dimethylamino)methylidene]-2-{[3/4-(trifluoromethyl)phenyl]amino}-1,3-thiazol-4(5H)-ones (Pyrih et al, 2023a, unpublished;CCDC deposition numbers 2293074 and 2293075;Groom et al, 2016). The presented results for the proton tautomerism seem to indicate that the influence of electron-accepting substituents on the stabilization of the tautomeric amine/imine equilibrium is not as obvious as the literature might suggest (Engoyan et al, 1978;Ramsh et al, 1985;Minkin et al, 2000).…”

“…This observation can be explained by the high portion of marketed drugs based on heterocyclic cores, mostly containing N atoms with a high propensity for proton tautomerism (de la Torre & Albericio, 2023). Amino derivatives of 4-thiazolidinones are also prone to tautomerism, but structural studies have focused so far on the synthetically more accessible 2-amino-4-thiazolidinones rather than on the isomeric 4-amino-2-thiazolidinones (Ramsh et al, 1985;Engoyan et al, 1978;Kowiel, 2015). These compounds are of great interest because of their pharmaceutical potential, which includes anticancer (Roszczenko et al, 2022), antibacterial (Tratrat et al, 2022), antitrypanosomal (Krysh-chyshyn et al, 2019) and many other biological activities (Nirwan et al, 2019;Seboletswe et al, 2023).…”

Proton tautomerism in 5-dimethylaminomethylidene-4-(o-,m-,p-hydroxyphenyl)amino-1,3-thiazol-2(5H)-ones: synthesis, crystal structure and spectroscopic studies

“…Insufficient attention to tautomerism leads to discrepancies in the literature, when the same aminothiazolidinones are reported at the same conditions as different tautomers from different sources, and is an additional rationale for more thorough structural studies (Behbehani & Ibrahim, 2012;Gzella et al, 2014). It is relevant in this context that Ramsh and coworkers established quite early that the simple 2amino-1,3-thiazol-4(5H)-ones exist in liquid phases as a mixture of tautomers (Engoyan et al, 1978;Ramsh et al, 1984Ramsh et al, , 1985. Later, the single crystal X-ray analysis of these derivatives presented by Kowiel (2015) revealed the influence of the chemical nature of the substituent at the aromatic ring on the tautomeric form, with electron-withdrawing groups facilitating the imino form.…”