Synthesis of 5‐aroylamino‐3H‐1,3,4‐thiadiazole‐2‐thiones and their tautomerism

Abstract

5‐Aroylamino‐3H‐1,3,4‐thiadiazole‐2‐thiones 2 have been synthesized by acylation of 5‐amino‐3H‐1,3,4‐thiadiazole‐2‐thione 1. 5‐Aroylamino‐3H‐1,3,4‐thiadiazole‐2‐thiones can exist in two tautomeric forms — a thiol form and a thione form. On the basis of the 13C nmr spectra and additional experimental information, it has been established that the thione form is the stable form in which these compounds exist.

Regioselective synthesis and biological evaluation of some novel thiophene-containing heterocyclic scaffolds as potential chemotherapeutic agents

“…This downfield NH resonance in the isolated product from the studied reaction can be rationalized in terms of the presence of the thione group attached to the nitrogen atom linked to the thioamide proton and as a result this proton is deshielded by the thione group and appears around that chemical shift value. This assignment is in line with literature assignments, that predict this signal would appear typically in the range δH ~ 13.00-14.00 ppm by analogy with related heterocyclic thioamides [31][32][33][34][35][36][37]. On the contrary, the isomeric structure 7, if isolated, would be expected to display an upfield shift for the NH proton due to the absence of deshielding thione group.…”

“…Conclusive evidence for the proposed structure 8 was provided by the 13 C NMR spectrum of the isolated product, where a diagnostic signal in the downfield region typically at δC 173.2 ppm was detected. Such a downfield signal can be assigned only to the thioamide CS carbon atom, which was reported to appear at δC value greater than 169 ppm in related systems [37][38][39][40]. It is worthwhile to report here that the thione form is the stable form in which compound 8 mainly exists since its IR spectrum revealed no absorption band at around ν 2600-2550 cm -1 , which is indicative of the thiol form [35,36,[41][42][43].…”

“…It is worthwhile to report here that the thione form is the stable form in which compound 8 mainly exists since its IR spectrum revealed no absorption band at around ν 2600-2550 cm -1 , which is indicative of the thiol form [35,36,[41][42][43]. In the 1 H NMR spectrum of 8, the absence of a signal due to the SH proton that would be expected to resonate in the range δH 1.6-4.0 ppm [35,37] also provided confirmatory evidence for thione formation. The prevalence of the thione rather than the thiol form in a number of heterocyclic systems is well-established [44][45][46].…”

Organotin(IV) triazolates: Synthesis and their spectral characterization

“…In the 13 C NMR spectrum of HL, three signals are observed at d 173.62, 161.72 and 151.14 ppm; as the ligand exists in thiol-thione tautomeric forms (Fig. 1), these signals are assigned to C(5) of thione form, C(3) thione/thiol form and C(5) of thiol form, respectively, on the basis of the literature values reported for the related molecules [19,31,49,50]. In the 13 C NMR spectra of organotin(IV) triazolates, C(3) and C(5) are observed in the range d 158.11-159.0 and 160.70-164.15 ppm, respectively.…”

Synthesis of Heteromacrocycles as Ligands of a Palladium-Artificial Enzyme and Crystal Structure

“…The crude product was recrystallized from C2H5OH to afford pure product (0. The synthesis of 5-amino-3H-1,3,4-thiadiazolin-2-thione Notes (2), 10 α,α'-bis(5-chloro-3-oxapentylthio-m-xylene (6a), 15 α,α'-bis(8-chloro-3,5-dioxaoctylthio)-m-xylene (6b), 15 α,α'-bis [5-(5-amino-1,3,4-thiadiazol-2-yl)thio-3-oxapentylthio)-m-xylene (7a), 15 α,α'-bis[8-(5-amino-1,3,4-thiadiazol-2-yl)thio-3,5-dioxaoctylthio]-m-xylene (7b) 15 were followed the previous procedures . 11,12,14,20,22,23-Hexaaza-6,28-dioxa-3,9,25,31,38,39-hexathiotetracyclo-[31,3,1,1 10(11),12(13),21(22),23(24),33(34),35(36)-heptaene-15,19-dione (8a).…”