Zur Chemie des Maleins�ure-monoureides, 2. Mitt.: Reaktionen an der Doppelbindung der Maleinurs�ure

An Efficient Ni(II) Laurate Promoted Heterocyclization of Symmetrical Thioureas with Maleic Anhydride and Mechanistic Approach toward Higher Substituted Thiazolidine‐4‐one‐5‐acetic Acids

“…[35] Moreover, some mono N-alkyl or mono N-aryl substituted thiourea derivatives can tautomerize over the substituted N atom to give a thia-Michael addition with maleic anhydride and subsequently form the corresponding thiazolidine derivative. [36] In the present study, although the reagents were heated in DMF for 24 hours, only traces of product formation were observed (Table 1, entry 4). Accordingly, it can be stated that polar protic solvents are generally not preferable for the construction of thiazolidines with higher hydrophobic aliphatic substituents.…”

“…However, when maleic anhydride and unsubstituted thiourea molecule are refluxed in concentrated hydrochloric acid, 2,4‐dioxothiazolidine‐5‐acetic acid is formed in good yield via the intermediate product of 2‐imino‐4‐oxothiazolidine‐5‐acetic acid [35] . Moreover, some mono N ‐alkyl or mono N ‐aryl substituted thiourea derivatives can tautomerize over the substituted N atom to give a thia ‐Michael addition with maleic anhydride and subsequently form the corresponding thiazolidine derivative [36] . In the present study, although the reagents were heated in DMF for 24 hours, only traces of product formation were observed (Table 1, entry 4).…”