The chemistry of isothiazoles

Recent Studies of Nitrogen and Sulfur Containing Heterocyclic Analogues as Novel Antidiabetic Agents: A Review

The prevalence of diabetes mellitus is on the rise, which demands the identification of novel antidiabetic drugs. There is a need for safer and more effective alternatives because the therapy methods now available to manage diabetes have limits. Due to their diverse pharmacological characteristics, heterocyclic molecules with nitrogen and Sulfur atoms have become intriguing candidates in medicinal chemistry. These substances have a wide variety of structures that can be customized to target different pathways associated with diabetes and can affect important biological targets involved in glucose homeostasis. This review provides a thorough summary of the most recent studies on heterocyclic analogues of nitrogen and Sulfur as prospective antidiabetic agents. This review examines the variety of their structural forms, their methods of action, and assesses the results of preclinical and clinical investigations on their effectiveness and safety. Additionally, further optimization and development of innovative antidiabetic medications are highlighted, as well as the difficulties and prospects for the future in utilizing the therapeutic potential of these analogues. This study seeks to stimulate additional investigation and cooperation between researchers and medicinal chemists, promoting improvements in the creation of efficient and secure antidiabetic medicines to fulfill the needs in the management of diabetes.

Carbon-Sulfur Bond Formation: Tandem Process for the Synthesis of Functionalized Isothiazoles

In this paper, we report a new process for the construction of 3,4,5-substituted isothiazoles via reaction cascades including Pummerer-like rearrangement, nucleophilic condensation, and sulfenamide cyclization followed by concomitant elimination and dehydration under mild reaction conditions. This process provides isothiazoles bearing fluorine and other functional groups in good to excellent yields from readily available starting materials.

Discovery of Novel 3,4-Dichloroisothiazole-Containing Coumarins as Fungicidal Leads

Natural products are one of the resources for discovering novel fungicidal leads. As a natural fungicide, osthole was used as a coumarin-based lead compound for the development of novel fungicides. Here, a series of 3,4-dichloroisothiazole-containing 7-hydroxycoumarins were rationally designed, synthesized, and characterized by introducing a bioactive substructure, 3,4-dichloroisothiazole, into the coumarin skeleton. In vitro bioassay indicated that compound 7g displayed good activity against Rhizoctonia solani, Physalospora piricola, Sclerotinia sclerotiorum, and Botrytis cinerea. Its median effective concentration (EC₅₀) value against each of these fungi fell between 0.88 and 2.50 μg/mL, which was much lower than that of osthole against the corresponding pathogen (between 7.38 and 74.59 μg/mL). In vivo screening validated that 7k exhibited 100%, 60%, and 20% efficacy against R. solani Kühn at 200, 100, and 50 μg/mL, respectively. RNA sequence analysis implied that growth inhibition of R. solani by 7k might result from potential disruptions of fungal membrane formation and intracellular metabolism. Furthermore, a field experiment with cucumber plants indicated that 7b showed 62.73% and 74.03% efficacy against Pseudoperonospora cubensis (Berk. & Curt.) Rostov. at rates of 12.5 g a.i./ha and 25 g a.i./ha, respectively, which showed no significant difference between 7b and osthole at 30 g a.i./ha. Our studies suggested that 7b, 7g, and 7k might be used as fungicidal leads for further optimization.

Design, synthesis and fungicidal activity of 3,4-dichloroisothiazolocoumarin-containing strobilurins

Twenty-one novel 3,4-dichloroisothiazolocoumarin-containing strobilurins were rationally designed and synthesized. Preliminary bioassay showed that compounds 7c, 7h and 7l exhibited over 80% inhibitory rate against Sclerotinia sclerotiorum at 50 μg/mL, 7c exhibited good activity against S. sclerotiorum with median effective concentration (EC₅₀) of 4.08 μg/mL, while the positive control coumoxystrobin showed EC₅₀ of 1.00 μg/mL. In addition, 7d showed better fungicidal activity with a lower EC₅₀ value of 7.65 μg/mL against Botrytis cinerea than that of positive control trifloxystrobin with its EC₅₀ value of 21.96 μg/mL. This study indicated that 3,4-dichloroisothiazolocoumarin-containing strobilurin was a promising fungicide lead deserved for further study.

A Feasible Method Applied to One-Bath Process of Wool/Acrylic Blended Fabrics with Novel Heterocyclic Reactive Dyes and Application Properties of Dyed Textiles

Reactive dyes containing cationic groups have great potentiality as novel dyes, which can be applicable to one-bath dyeing of wool/acrylic blended fabrics. In this work, four novel heterocyclic reactive dyes containing cationic groups were designed by using m-aminophenyltrimethylammonium salt or N-(2-aminoethyl) pyridinium chloride salt as cationic groups, N, N-diethyl-1,3-benzenediamine as a coupling component, 2-amino-6-methoxybenzothiazole, 2-aminobenzothiazole or 3-amino-5-nitrobenzoisothiazole as diazo components. These dyes based on benzothiazole derivative chromophores not only showed beautiful color, including blue-green and fuchsia, but also had larger tinctorial strength with a high molar extinction coefficient, further reducing the dosage of dyes to achieve same color depth. Factors affecting the dyeability on fabrics, such as pH value, dyeing temperature and dye concentration were discussed. Excellent dyeing behavior, levelling properties and good fastness on wool/acrylic blended fabric were obtained. What’ more, excellent anti-ultraviolet and antibacterial properties were obtained for textiles with these dyes. The application of these dyes with large molar extinction coefficients presents a wide range of possibilities for the further development of cleaner production and eco-friendly dyeing, even functional textiles.

Access to 4-substituted isothiazoles through three-component cascade annulation and their application in C–H activation

The use of EtOCS₂k enabled the annulation of isopropene derivatives with NH₄I, affording various 4-substituted isothiazoles in good yields.

Role of sulphur-heterocycles in medicinal chemistry: An update

From many decades, S-heterocycles have maintained their status as an important part and core of FDA approved drugs and medicinally active compounds. With exhaustive exploration of nitrogen heterocycles in medicinal chemistry, researchers have shifted their interest towards other heterocycles, especially, S-heterocycles. Thus several attempts have been made to synthesize a variety of new sulphur containing compounds with high medicinal value and low toxicity profile, in comparison to previous N-heterocycles. Till today, S-heterocycle containing compounds have been largely reported as anticancer, antidiabetic, antimicrobial, antihypertension, antivral, antinflammatory etc. In this review, the authors have tried to provide a critical analysis of synthesis and medicinal attributes of sulphur containing heterocycles such as thiirane, thiophene, thiazole, thiopyran, thiazolidine etc reported within last five years to emphasize the significance and usefulness of these S-heterocycles in the drug discovery process.

Synthesis of Novel 3,4-Chloroisothiazole-Based Imidazoles as Fungicides and Evaluation of Their Mode of Action

A molecular design approach was used in our laboratory to guide the development of imidazole-based fungicides. Based on homology modeling and molecular docking studies targeting the cytochrome P450-dependent sterol 14α-demethylase, 3,4-dichloroisothiazole-based imidazoles showed great potential. Several such compounds were then rationally designed, synthesized, characterized, and their antifungal activities were evaluated. Bioassay results showed that compounds such as ( R)-11, ( R)-12, and ( S)-11 have commendable, broad-spectrum antifungal activities that are comparable to those of commercial products. Based on Q-PCR testing and microscopy observations, the imidazole derivatives affect fungal cell wall formation through the inhibition of the BcCYP51 expression system. These findings strongly suggest that the mode of action of these imidazole compounds is similar to that of tioconazole and imazalil. This report indicates that this molecular design strategy is not only practical but productive.

The crystal structures of two isomers of 5-(phenyl-iso-thia-zol-yl)-1,3,4-oxa-thia-zol-2-one

The syntheses and crystal structures of two isomers of phenyl iso-thia-zolyl oxa-thia-zolone, C11H6N2O2S2, are described [systematic names: 5-(3-phenyl-iso-thia-zol-5-yl)-1,3,4-oxa-thia-zol-2-one, (I), and 5-(3-phenyl-iso-thia-zol-4-yl)-1,3,4-oxa-thia-zol-2-one, (II)]. There are two almost planar (r.m.s. deviations = 0.032 and 0.063 Å) mol-ecules of isomer (I) in the asymmetric unit, which form centrosymmetric tetra-mers linked by strong S⋯N [3.072 (2) Å] and S⋯O contacts [3.089 (1) Å]. The tetra-mers are π-stacked parallel to the a-axis direction. The single mol-ecule in the asymmetric unit of isomer (II) is twisted into a non-planar conformation by steric repulsion [dihedral angles between the central iso-thia-zolyl ring and the pendant oxa-thia-zolone and phenyl rings are 13.27 (6) and 61.18 (7)°, respectively], which disrupts the π-conjugation between the heteroaromatic iso-thia-zoloyl ring and the non-aromatic oxa-thia-zolone heterocycle. In the crystal of isomer (II), the strong S⋯O [3.020 (1) Å] and S⋯C contacts [3.299 (2) Å] and the non-planar structure of the mol-ecule lead to a form of π-stacking not observed in isomer (I) or other oxa-thia-zolone derivatives.

Copper-catalyzed asymmetric alkynylation of cyclic N-sulfonyl ketimines

A Cu-catalyzed asymmetric alkynylation of cyclic N-sulfonyl ketimines was developed, providing the corresponding chiral α-tertiary amines with up to 98% ee.

A second polymorph of (Z)-3-amino-4-(2-phenyl-hydrazinyl-idene)-1H-pyrazol-5(4H)-one

The mol­ecule of the title compound, C₉H₉N₅O, is approximately planar (the r.m.s. deviation of all non-H atoms is 0.08 Å). The amine substituent is pyramidal at the N atom. An intra­molecular N—H_hydrazine⋯O=C hydrogen bond is present. In the crystal, mol­ecules are connected via N—H⋯N and N—H⋯O hydrogen bonds, forming infinite layers parallel to (010). This polymorph is triclinic, space group P-1, whereas the previously reported form was monoclinic, space group P2₁/c [Elgemeie et al. (2013 ▶). Acta Cryst. E69, o187], with stepped layers and a significantly lower density.

A model study on the photochemical isomerization of isothiazoles and thiazoles

The mechanisms for photochemical isomerization reactions are studied theoretically using three model systems: 3-methylisothiazole, 4-methylisothiazole and 5-methylisothiazole.

Ring transformation of (4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitriles to 3-haloisothiazole-5-carbonitriles

Improved conditions for the ring transformation of 1,2,3-dithiazoles into isothiazole-5-carbonitriles are presented together with mechanistic rationale.

2-[(3-Bromo-anilino)meth-yl]-1,2-benzo-thia-zol-3(2H)-one

The title compound, C₁₄H₁₁BrN₂OS, was synthesized by the reaction of 1,2-benzothia­zol-3(2H)-one with formalin and 3-bromo­aniline in ethanol. The 1,2-benzothia­zolone ring system is approximately planar [maximum deviation = 0.0142 (s.u.?) Å] and forms a dihedral angle of 79.19 (5)° with the benzene ring. In the crystal, molecules are linked by N—H⋯O, C—H⋯O and C—H⋯Br interactions.

Butyl 3-oxo-2,3-dihydro-benzo[d][1,2]thia-zole-2-carboxyl-ate

The title compound, C(12)H(13)NO(3)S, was synthesised by the reaction of benzo[d]isothia-zol-3(2H)-one with butyl alcohol in toluene. The benzoisothia-zolone ring system is almost planar with a mean deviation of 0.041 (1) Å. In the crystal, mol-ecules are linked by weak inter-molecular C-H⋯O hydrogen bonds.

2-(3-Oxo-2,3-dihydro-1,2-benzothia-zol-2-yl)acetic acid

In the title compound, C(9)H(7)NO(3)S, the benzoisothia-zolone ring system is essentially planar, with a maximum deviation of 0.013 (2) Å. In the crystal, mol-ecules are linked via O-H⋯O hydrogen bonds, forming chains along [010]. In addition, weak inter-molecular C-H⋯O hydrogen bonds are present.

Propyl 3-oxo-2,3-dihydro-1,2-benzothia-zole-2-carboxyl-ate

The title compound, C(11)H(11)NO(3)S, was synthesized by the reaction of benzo[d]isothia-zol-3(2H)-one with propyl carbono-chloridate in toluene. The benzoisothiazolone ring system is approximately planar with a maximum deviation from the mean plane of 0.0226 (14) Å for the N atom. Weak inter-molecular C-H⋯O hydrogen bonding occurs in the crystal structure.

Ethyl 3-oxo-2,3-dihydro-1,2-benzothia-zole-2-carboxyl-ate

The title compound, C₁₀H₉NO₃S, was synthesized by the reaction of benzo[d]isothia­zol-3(2H)-one with ethyl carbonochloridate in toluol. The benzisothia­zolone ring system is approximately planar, with a maximum deviation from the mean plane of 0.020 (1) Å for the N atom.

Isopropyl 3-oxo-2,3-dihydro-1,2-benzothia-zole-2-carboxyl-ate

The title compound, C(11)H(11)NO(3)S, was synthesized by the reaction of benzo[d]isothia-zol-3(2H)-one with isopropanol in toluene. The benzoisothia-zolone ring system is essentially planar, with a mean deviation of 0.018 (2) Å from the least-squares plane defined by the nine constituent atoms. In the crystal, mol-ecules are linked by weak inter-molecular C-H⋯O hydrogen bonds.