Chemistry and uses of 1-(2-benzothiazolyl)pyrazolines: a mini-review

The current report provides an overview of the rapidly developing class of pyrazolines having a benzothiazole moiety at N¹. The synthetic approaches (mainly through the [3 + 2] cyclo-condensation of chalcone analogs with 2-hydrazinobenzothiazole) toward these particular pyrazolines, along with their chemical transformation to pyrazoles through oxidation are outlined. The photophysical properties (absorption and emission spectra) along with their applications as fluorescent chemosensors have been summarized. 1-(2-Benzothiazolyl)pyrazolines exhibit significant fluorescence quenching mostly in the presence of transition metal ions, such as Fe³⁺, Cu²⁺, Hg²⁺, Zn²⁺, or Ni²⁺, but also toward Al³⁺, thus enabling the selective detection of these analytes. In addition, examples of 1-(2-benzothiazolyl)pyrazolines acting as chemosensors for anions such as S²⁻ or F⁻ are also available. Comprehensive examination of the biological properties of 1-(2-benzothiazolyl)pyrazolines shows that members of this class possess either broad or selective significant antimicrobial activity, along with tuberculostatic activity and cytotoxicity that is sometimes better than that of positive controls. The antidiabetic, anti-inflammatory, anthelmintic, and antimalarial activity of these compounds, along with their potential for inhibition of enzymes such as carbonic anhydrase or acetylcholinesterase have been briefly explored.