Electrooxidative Cyclization of Benzylideneaminothiophenols to the Corresponding 2-Arylbenzothiazoles

2-Arylbenzothiazole as a Privileged Scaffold in Drug Discovery

“…The microwave-promoted catalyst-free synthesis of 2-arylbenzothiazoles in the ionic liquid [pmIm]Br has been described [61]. Electrochemical-based oxidation methods have been reported for the key cyclisation of intermediate 2-(benzylidenamino)thiophenols to give a range of substituted 2-arylbenzothiazoles [62].…”

An efficient green protocol for the synthesis of 2-aryl substituted benzothiazoles

“…Okimoto et al (45) have carried the cyclocondensation of the imines generated from aldehydes and amines using electro oxidative cyclization. The cyclocondensation of aryl aldehydes and 2-aminothiophenol have been performed by Itoh et al (46) using scandium triflate and obtained better yields of the benzothiazoles.…”

Cerium (IV) Ammonium Nitrate (CAN) Catalyzed One-pot Synthesis of 2-Arylbenzothiazoles

“…On the other hand, the most general synthetic approaches to 2-arylbenzothiazoles involve: (1) arylation of benzothiazole with aryl bromides at 150 o C in a sealed tube catalyzed by Pd(OAc) 2 , Cs 2 CO 3 and CuBr with P( t -Bu) 3 as ligand [10], or Suziki biaryl coupling of 2‑bromobenzothiazole with aryl boronic acids [11]; (2) condensation of 2-aminothiophenols with carboxylic acids under microwave irradiation [12] or with polymer-bound esters in the presence of a Lewis acid [13]; (3) oxidative cyclization of phenolic Schiff’s bases derived from the condensation of 2-aminothiophenols and aldehydes using various oxidants such as Sc(OTf) 3 using molecular oxygen[14], activated carbon [15], pyridinium chlorochromate [16] and very recently via electrooxidation [17]; recently [18] a modification of such strategy that involves flash vacuum pyrolysis and photolysis of 2-methylthio- N -(arenylidene)anilines has been reported; (4) direct condensation of 2-aminothiophenol with aromatic aldehydes under microwave irradiation [19]. However, most of these synthetic approaches suffer from drawbacks such as harsh reaction conditions (strong acids, high temperatures), lengthy procedures that consume excess reagents, expensive catalysts that may be harmful to the environment or a sophisticated techniques.…”