An efficient, regioselective, one-pot and two-step synthesis of β-hydroxy 1,4-disubstituted 1,2,3-triazoles from a wide range of non-activated terminal alkynes and epoxides and sodium azide by way of a three-component click reaction using a catalytic amount of [meso-tetrakis(o-chlorophenyl)porphyrinato]copper(II) (5 mol%) in excellent isolated yields is described. The reactions were performed in water as a green solvent at ambient temperature without any additives. By performing two reaction steps in one pot and purifying only at the final step, this procedure excludes any interim purification of in situ generated organic azide intermediates, which significantly improves the overall yield and reduces the reaction time. To benefit from the recovery and reuse of the catalyst, a new heterogeneous catalyst was prepared by simple and successful impregnation of the catalyst onto activated multi-walled carbon nanotubes (AMWCNT). The heterogeneous catalyst was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic forced microscopy (AFM), and thermogravimetric (TG) analysis to estimate the amount of nitrogen adsorption, and Raman and FT-IR spectroscopy. Leaching experiments after ten successive cycles showed that the catalyst is most strongly anchored to the AMWCNT support. Mechanistically, porphyrinatocopper catalyzes each step of the reaction in different ways as a bifunctional catalyst including epoxide ring opening by azide delivery to epoxide, forming in situ generated 2-azido alcohols followed by activation of the C≡C triple bond of the starting terminal alkynes by forming a porphyrinatocopper-acetylide intermediate and thereby promoting the [3+2]-cycloaddition reaction as the key step to form the triazole framework.

Immobilization of Porphyrinatocopper Nanoparticles onto Activated Multi‐Walled Carbon Nanotubes and a Study of its Catalytic Activity as an Efficient Heterogeneous Catalyst for a Click Approach to the Three‐Component Synthesis of 1,2,3‐Triazoles in Water

Convenient Synthesis of Benzothiazoles and Benzimidazoles through Brønsted Acid Catalyzed Cyclization of 2-Amino Thiophenols/Anilines with β-Diketones

Benzothiazole can serve as unique and versatile scaffolds, especially in synthetic and pharmaceutical chemistry because of their potent and significant pharmacological activities. This important class of derivatives possess numerous pharmacological activities like antitumor, antimicrobial, anti-inflammatory, anticonvulsant, antidiabetic activities and so on. Many scientists have developed a wide range of methodologies for the synthesis of the 2-substituted benzothiazole nucleus and its derivatives using different types of catalysts to improve the selectivity, purity and yield of the products. Thus, the present review article focuses mainly on the different kind of reactions involved in synthesis of the 2-substituted benzothiazole nucleus and its derivatives.

Recent advances in the synthesis of 2-substituted benzothiazoles: a review

Iron sulfide generated in situ from elemental sulfur and iron was found to be highly efficient in catalyzing a redox/condensation cascade reaction between 2-amino/hydroxy nitrobenzenes and activated methyl groups. This method represents a straightforward and highly atom economical approach to 2-hetaryl-benzimidazoles and -benzoxazoles.

Iron Sulfide Catalyzed Redox/Condensation Cascade Reaction between 2-Amino/Hydroxy Nitrobenzenes and Activated Methyl Groups: A Straightforward Atom Economical Approach to 2-Hetaryl-benzimidazoles and -benzoxazoles

Room temperature synthesis of benzimidazole derivatives using reusable cobalt hydroxide (II) and cobalt oxide (II) as efficient solid catalysts

Methanesulfonic Acid/SiO2 as an Efficient Combination for the Synthesis of 2-Substituted Aromatic and Aliphatic Benzothiazoles from Carboxylic Acids

New One‐Pot Procedure for the Synthesis of 2‐Substituted Benzimidazoles

Simple and mild procedures for synthesis of benzimidazole derivatives using heterogeneous catalyst systems

A highly selective synthesis of 2‐substituted benzimidazole derivatives from the reaction of o‐phenylendiamine derivatives and aromatic aldehydes in the presence of an organic salt, NH4OAc, in absolute ethanol is presented. The products were obtained by evaporating the solvent followed by a simple recrystallization with excellent yields.

New One-Pot Procedure for the Synthesis of 2-Substituted Benzimidazoles.

Methanesulfonic acid/SiO2 (1 mL/0.3 g) was found to be as an expeditious mixture in the synthesis of 2-substituted aromatic and aliphatic benzothiazoles at 140 °C using carboxylic acids. After a simple workup, benzothiazoles were obtained in good yields. Simplicity, use of widely available and diverse carboxylic acids, and easy handling of the reaction conditions are among the benefits of the method.

Omid Asemani

Papers

Methanesulfonic Acid/SiO2 as an Efficient Combination for the Synthesis of 2-Substituted Aromatic and Aliphatic Benzothiazoles from Carboxylic Acids

New One‐Pot Procedure for the Synthesis of 2‐Substituted Benzimidazoles

Simple and mild procedures for synthesis of benzimidazole derivatives using heterogeneous catalyst systems

New One-Pot Procedure for the Synthesis of 2-Substituted Benzimidazoles.

Methanesulfonic Acid/SiO2 as an Efficient Combination for the Synthesis of 2‐Substituted Aromatic and Aliphatic Benzothiazoles from Carboxylic Acids.