Crystal structure, spectroscopic studies and theoretical studies of thiobarbituric acid derivatives: understanding the hydrogen‐bonding patterns. Issue 12 (22nd November 2018)

• Record Type: Journal Article
• Authors: Sharma, Anamika; Zamisa, Sizwe J.; Noki, Sikabwe; Almarhoon, Zainab; El-Faham, Ayman; Torre, Beatriz G. de la; Albericio, Fernando
• Is Part Of: Acta crystallographica. Volume 74:Issue 12(2018)
• Page Start: 1703
• Page End: 1714
• Publication Date: 2018-11-22
• Subjects: thiobarbituric acid -- X‐ray crystallography -- UV spectroscopy -- crystal structure -- IR spectroscopy -- DFT calculations -- transition state; Crystallography -- Periodicals; Crystals -- Periodicals; 548.3
• DOI: 10.1107/S2053229618015516
• Languages: English
• ISSNs: 2053-2296

Abstract

Abstract : The absolute configurations for six thiobarbituric acid (TBA) derivatives were confirmed by single‐crystal X‐ray crystallography, which indicates the formation of intramolecular hydrogen bonding in all cases and intermolecular hydrogen bonding in one case. Abstract : In addition to their wide‐ranging applications in the pharmaceutical industry, thiobarbituric acid (TBA) derivatives are also known to possess applications in engineering and materials science. 20 TBA derivatives, with diversity at the N and C‐5 positions through acylation, Schiff base formation, Knoevenagel condensation, thioamide and enamine formation, were studied. The absolute configurations for six derivatives, namely 5‐acetyl‐1, 3‐diethyl‐2‐thioxodihydropyrimidine‐4, 6(1 H, 5 H )‐dione, C10 H14 N2 O3 S, A01, 1, 3‐diethyl‐5‐propionyl‐2‐thioxodihydropyrimidine‐4, 6(1 H, 5 H )‐dione, C11 H16 N2 O3 S, A02, tert ‐butyl [1‐(1, 3‐diethyl‐4, 6‐dioxo‐2‐thioxohexahydropyrimidin‐5‐yl)‐3‐methyl‐1‐oxobutan‐2‐yl]carbamate, C18 H29 N3 O5 S, A06, 1, 3‐diethyl‐4, 6‐dioxo‐2‐thioxo‐ N ‐( p ‐tolyl)hexahydropyrimidine‐5‐carbothioamide, C16 H19 N3 O2 S2, A13, 5‐(1‐aminoethylidene)‐1, 3‐diethyl‐2‐thioxodihydropyrimidine‐4, 6(1 H, 5 H )‐dione, C10 H15 N3 O2 S, A17, and 5‐(1‐aminopropylidene)‐1, 3‐diethyl‐2‐thioxodihydropyrimidine‐4, 6(1 H, 5 H )‐dione, C11 H17 N3 O2 S, A18, were confirmed by single‐crystal X‐ray crystallography, which indicates the formation of intramolecular hydrogen bonding in all six cases and intermolecular hydrogen bonding forA17 . InA13, the presence of two intramolecular hydrogen bonds was observed. The stabilization of the enol form over the keto form was confirmed by computation. In order to convert the keto form to the enol form, an energy barrier of 55.05 kcal mol −1 needs to be overcome, as confirmed by transition‐state calculations.