Microwave-Assisted Synthesis of Disulfides

Kinetic Insights into the Antioxidant Effect of Isatin-Thiosemicarbazone in Biodiesel Blends

Biodiesel has several drawbacks, such as being prone to oxidation, having reduced stability, and having limited storage time. Antioxidants compatible with biodiesel are being used to address its drawbacks. Utilizing antioxidants effectively improves the quality of biodiesel. Enhancing the quality of biodiesel for use as a clean energy source benefits both the global economy and ecology. Therefore, we believe that our work will contribute to the advancement of the biodiesel industry worldwide. This study used blends consisting of 20% biodiesel and 80% diesel fuel. Isatin-thiosemicarbazones were tested as additives in blends at a concentration of 3000 parts per million (ppm) using an oxifast device and were compared with the chemical antioxidant Trolox. FT-IR, DSC, and TGA were used to characterize these samples. DSC measured sample crystallization temperatures (Tc). Samples with antioxidants showed decreased values compared to the non-antioxidant diesel sample D100. Several DSC tests were conducted to determine the antioxidant strengths of various samples. The results show that the FT-IR spectrum's antioxidant effect regions grow clearer with antioxidants. The extra antioxidant is effective. Biodiesel's oxidative stability improves with isatin-thiosemicarbazones at varying concentrations. The kinetics of thermal decomposition of isatin-thiosemicarbazones under non-isothermal conditions were determined using the Kissinger, Ozawa, and Boswell techniques. The activation energies of compounds 1 and 2 were calculated as 137-147 kJ mol-1 and 173-183 kJ mol-1, respectively.

Inhibitory effects of sulfenimides on human and bovine carbonic anhydrase enzymes

A series of sulfenimide derivatives (1a-i) were investigated as inhibitors of human (hCA-I, hCA-II) and bovine (bCA) carbonic anhydrase enzymes. The compounds were synthesised by the reaction of substituted thiophenols with phthalimide by means of an effective, simple and eco-friendly method and the structures were confirmed by IR, ¹H NMR, ¹³C NMR, MS and elemental analysis. All derivatives except for the methyl derivative (1b) exhibited effective inhibitory action at low micromolar concentrations on human isoforms, but only four derivatives (1e, 1f, 1h, 1i) inhibited the bovine enzyme. The bromo derivative (1f) was found to be strongest inhibitor of all three enzymes with KI values of 0.023, 0.044 and 20.57 µM for hCA-I, hCA-II and bCA, respectively. Results of our study will make valuable contributions to carbonic anhydrase inhibition studies for further investigations since inhibitors of this enzyme are important molecules for medicinal chemistry.

S-(4-Methoxyphenyl)-4-methoxybenzenesulfonothioate as a Promising Lead Compound for the Development of a Renal Carcinoma Agent

Organosulfur compounds show cytotoxic potential towards many tumor cell lines. Disulfides and thiosulfonates act through apoptotic processes, inducing proteins associated with apoptosis, endoplasmic reticulum stress, and the unfolded protein response. Three p-substituted symmetric diaryl disulfides and three diaryl thiosulfonates were synthesized and analyzed for inhibition of tubulin polymerization and for human cancer cell cytotoxic activity against seven tumor cell lines and a non-tumor cell line. S-(4-methoxyphenyl)-4-methoxybenzenesulfonothioate (6) exhibited inhibition of tubulin polymerization and showed the best antiproliferative potential, especially against the 786-0 cell line, being six times more selective as compared with the non-tumor cell line. In addition, compound 6 was able to activate caspase-3 after 24 and 48 h treatments of the 786-0 cell line and induced cell-cycle arrest in the G2/M stage at the highest concentration evaluated at 24 and 48 h. Compound 6 was able to cause complete inhibition of proliferation, inducing the death of 786-0 cells, by increasing the number of cells at G2/M and greater activation of caspase-3.

Unsymmetrical Disulfides Synthesis via Sulfenium Ion

An umpolung approach for the synthesis of unsymmetrical disulfides via sulfenium ion is reported. In situ generated electrophilic sulfenium ion from electron-rich thiols reacted with second thiols to yield unsymmetrical disulfides. Using an iodine catalyst and 4-dimethylaminopyridine (DMAP)/water as promoter, the target syntheses were achieved in one pot under aerobic condition.

Silver-mediated oxidative vinylic C–H bond sulfenylation of enamides with disulfides

A silver-mediated oxidative vinylic C–H bond sulfenylation of enamides was developed. This method is compatible with diaryl and dialkyl disulfides to deliver the biologically precious chalcogenated olefins efficiently. A plausible non-chain radical mechanism was proposed for understanding this novel sulfenylation based on the mechanistic studies.