Catalyst- and Additive-Free Method for the Synthesis of 2-Substituted Benzothiazoles from Aromatic Amines, Aliphatic Amines, and Elemental Sulfur

Recent Advances in the Application of 2-Aminobenzothiazole to the Multicomponent Synthesis of Heterocycles

Heterocycles are a vital class of compounds in numerous fields, including drug discovery, agriculture, and materials science. Efficient methods for the synthesis of heterocycles remain critical for meeting the demands of these industries. Recent advances in multicomponent reactions (MCRs) utilizing 2-aminobenzothiazole (ABT) have shown promising results for the formation of heterocycles. The versatility of 2-aminobenzothiazole in this context has enabled the rapid and efficient construction of diverse heterocyclic structures. Various synthetic methodologies and reactions involving 2-aminobenzothiazole are discussed, highlighting its importance as a valuable building block in the synthesis of complex heterocycles. The potential applications of these heterocycles in drug discovery and material science are also explored. Overall, this review provides a comprehensive overview of the current state of research in the field and offers insights into the future directions of this promising area of study. We highlight the potential of ABT as a versatile and sustainable starting material in heterocyclic synthesis via MCRs, with significant implications for the chemical industry.

Visible-Light-Promoted Cascade Coupling of 2-Isocyanonaphthalenes with Elemental Sulfur and Amines to Construct Naphtho[2,1-d]thiazol-2-Amines

A visible-light-induced strategy has been explored for the synthesis of naphtho[2,1-d]thiazol-2-amines through ortho-C-H sulfuration of 2-isocyanonaphthalenes with elemental sulfur and amines under external photocatalyst-free conditions. This three-component reaction, which utilizes elemental sulfur as the odorless sulfur source, molecular oxygen as the clean oxidant, and visible light as the clean energy source, provides a mild and efficient approach to construct a series of naphtho[2,1-d]thiazol-2-amines. Preliminary mechanistic studies indicated that visible-light-promoted photoexcitation of reaction intermediates consisting of thioureas and DBU might be involved in this transformation.

Metal- and base-free, aerobic photoredox catalysis with riboflavin to synthesize 2-substituted benzothiazoles

Sustainable approaches for the synthesis of 2-substituted benzothiazoles are sought after for their use in organic chemistry, bioorganic chemistry, and industrial applications. Here, we described a visible light-driven photoredox catalytic cyclization of thioanilides to afford 2-substituted benzothiazoles using riboflavin as a photocatalyst, where oxygen is used as a clean oxidant and ethanol as a greener solvent. These results provide a new photochemical route for environmentally benign synthesis.

NH4I-promoted oxidative formation of benzothiazoles and thiazoles from arylacetic acids and phenylalanines with elemental sulfur

A NH4I/K3PO4-based catalytic system has been established to enable oxidative formation of thiazole compounds from arylacetic acids and phenylalanines with elemental sulfur. While the three-component reaction of anilines or β-naphthylamines with arylacetic acids and elemental sulfur affords benzo[2,1-d]thiazoles and naphtho[2,1-d]thiazoles, the annulation of phenylalanines with elemental sulfur produces 2-benzyl and 2-benzoylthiazoles. This work well complements previous three-component annulations of benzothiazoles from other coupling partners.

Current advances in the synthetic strategies of 2-arylbenzothiazole

Benzothiazole is a privileged scaffold in the field of synthetic and medicinal chemistry. Its derivatives and metal complexes possess a gamut of pharmacological properties and high degree of structural diversity that has proven it vital for the investigation for novel therapeutics. The 2nd position of benzothiazole is the most active site that makes 2-arylbenzothiazole as felicitous scaffolds in pharmaceutical chemistry. The extensive significance of benzo-fused heterocyclic moieties formation has led to broad and valuable different approaches for their synthesis. This review deals with the synthetic approaches developed so far for the synthesis of 2-arylbenzothiazoles. Moreover, this article abridges the publications devoted to the synthesis of this moiety over the last 6 years. This study gives a current precis of research on the fabrication of 2-arylbenzothiazoles through different synthetic pathways and shall be helpful for researchers and scientists who are working in this field to make more potent biologically active benzothiazole-based drugs.