Synthesis of New Tetrafluorobenzo Heteroaromatic Compounds

Sulfur- and Amine- Promoted Multielectron Autoredox Transformation of Nitromethane: Multicomponent Access to Thiourea Derivatives

Thiourea derivatives are in-demand motifs in organic synthesis, medicinal chemistry and material science, yet redox methods for the synthesis that start from safe, simple, inexpensive and readily available feedstocks are scarce. In this article, we disclose the synthesis of these motifs using elemental sulfur and nitromethane as the starting materials. The method harnesses the multi-electron auto-redox property of nitromethane in the presence of sulfur and amines, delivering thiourea products without any added oxidant or reductant. Extension of this reaction to cyclizable amines and/or higher homologues of nitromethane led to a wide range of nitrogen heterocycles and thioamides. Operationally simple, the reactions are scalable, tolerate a wide range of functional groups, and can be employed for the direct functionalization of natural products. Mechanistically, the nitro group was found to act as an oxidant leaving group, being reduced to ammonia whereas sulfur, along with the role of a sulfur building block for the thiocarbonyl group, behaved as a complementary reductant, being oxidized to sulfate.

Chemistry and Chemical Biology of Selenenyl Sulfides and Thioseleninic Acids

Significance: Selenenyl sulfides (RSeSRs) and thioseleninic acids (RSeSHs) are the monoselenium (Se) analogs of disulfides and persulfides that contain Se-S bonds. These bonds are found in several antioxidant-regenerating enzymes as derivatives of selenocysteine, making them an important player in redox biology as it pertains to sulfur redox regulation. Recent Advances: Mechanistic studies of redox-regulating selenoenzymes such as thioredoxin reductase and glutathione peroxidase suggest crucial Se-S bonds in the active sites. Peptide models and small-molecule mimics of these active sites have been prepared to study their fundamental chemistry. These advances help pave the road to better understand the functions of the Se-S bond in the body. Critical Issues: The Se-S bond is unstable at atmospheric temperatures and pressures. Therefore, studying their properties proposes a major challenge. Currently, there are no trapping reagents specific to RSeSRs or RSeSHs, making their presence, identity, and fates in biological environments difficult to track. Future Directions: Further understanding of the fundamental chemistry/biochemistry of RSeSRs and RSeSHs is needed to understand what their intracellular targets are and to what extent they impact signaling. Besides antioxidant regeneration and peroxide radical reduction, the roles of RSeSR and RSeSHs in other systems need to be further explored.

Perimidines: a unique π-amphoteric heteroaromatic system

Data on the physicochemical characteristics, theoretical calculations, reactivity and synthetic methods for perimidines are summarized. Although perimidine and some of its simple 2-substituted derivatives were obtained by Sachs back in 1909, their chemistry and key physical properties remained unknown until the early 1970s. Subsequent studies revealed many fundamental features of the perimidine system, previously not encountered in the heterocyclic series. The first comprehensive review on perimidines was published forty years ago. The period that has passed since 1980 led to the emergence of new directions and trends. Several hundred new publications have appeared, the generalization of which has become the main purpose of this article. This primarily concerns the obtaining of highly nucleophilic and stable perimidine carbenes, new methods of electrophilic substitution and oxidation, establishment of a close relationship between perimidines and proton sponges, and modern theoretical calculations. Based on perimidines, many different polycondensed systems have been obtained. Applied research has developed especially rapidly in recent years. Many new compounds based on perimidines related to chemosensors, analytical reagents, dyes, metal catalysts, electronic devices, nanotechnology, and medical chemistry have been proposed. Some information under review is presented as Supplementary Materials. It contains six tables, which include data on the basicity constants of perimidines, details of some synthetic methods for perimidines and fused analogs and also a list of biological activities of perimidines.

The bibliography includes 387 references.

Silver-Promoted Site-Selective Intramolecular Cyclization of 2-Methylthiobenzamide Through α-C(sp3)-H Functionalization

Silver-mediated intramolecular α-C(sp³)-H bond functionalization of the methylthio group has been established in the presence of Selectfluor as an additive. This novel strategy provides efficient access to various diverse sulfur-based heterocycles with good yields and functional group compatibility. It is noteworthy that the completely novel benzooxathiin-4-imine skeletons were reported for the first time in this study.

Synthesis and Biological Activity of 2-Amino- and 2-aryl (Heteryl) Substituted 1,3-Benzothiazin-4-ones

Tuberculosis (TB) takes the second place among the reasons for mortality from infectious diseases. For this reason, the problem of tuberculosis treatment requires urgent attention all over the world. Some 2-amino substituted 1,3-benzothiazin-4-ones (2-amino-1,3-BTZs) represent a promising new class of antitubercular agents. Other 1,3-benzothiazin-4-one derivatives, mostly 2-aryl and 2- (pyridin-2-yl) ones, are attractive due to their ability to suppress oxidative stress-induced cardiomyocyte apoptosis. This review covers the synthetic approaches to 2-amino- and 2-aryl(heteryl) substituted 1,3-benzothiazin-4-ones (1,3-BTZs). A brief overview of structure-activity relationships is presented.

Double 1,4-addition of (thio)salicylamides/thiosalicylic acids with propiolate derivatives: a direct, general synthesis of diverse heterocyclic scaffolds

A simple and practical ring-closure procedure to prepare a range of diverse heterocycles has been developed.

3-Fluoro-12H-benzimidazo[2,1-b][1,3]benzothia-zin-12-one

In the title compound, C(14)H(7)FN(2)OS, prepared by the reaction of 2-bromo-4-fluoro-benzoyl choride with 2-mercaptobenzimidazole, the four-membered fused-ring system is essentially planar [maximum deviation from the mean plane = 0.035 (2) Å]. The crystal packing is stabilized by weak inter-molecular π-π [minimum ring centroid-centroid separation = 3.509 (7) Å], weak C-F⋯π [F⋯centroid = 3.4464 (17) Å, C-F⋯centroid = 97.72 (11)°] and C-O⋯π [O⋯centroid = 3.5230 (16) and 3.7296 (17) Å, C-O⋯centroid = 86.40 (10) and 86.25 (10)°] inter-actions and weak inter-molecular C-H⋯N hydrogen bonds.

2-Methyl-12H-benzimidazo[2,1-b][1,3]benzothia-zin-12-one

In the title compound, C₁₅H₁₀N₂OS, prepared by the reaction of 2-iodo-5-methyl­benzoyl chloride with 2-mercaptobenzimidazole, the four-membered fused-ring system is essentially planar [maximum deviation from the least-squares plane = 0.137 (6) Å]. The crystal packing is stabilized by weak inter­molecular π–π inter­actions [minimum ring centroid separation = 3.536 (4) Å] and weak C—H⋯π inter­actions.