Recent Advances in the Synthesis and Applications of 2-Arylbenzothiazoles

Abstract

This review firstly covers the applications of 2-arylbenzothiazoles as amyloid imaging agents, antitumor agents, and organic luminescent materials. Then we review the recent advances in the synthesis of 2-arylbenzothiazole derivatives. On the one hand, we introduce the approaches for construction of the 2-arylbenzothiazole core, including the following categories: (i) classic condensation of 2-aminothiophenols, (ii) direct arylation of benzothiazoles, (iii) intramolecular cyclization of thiobenzanilides, and (iv) tandem cyclization of anilines/ nitroarenes­ with elemental sulfur or sulfides. On the other hand, the transition-metal-catalyzed direct C–H functionalizations of 2-aryl­benzothiazoles are also involved in this review.1 Introduction2 Applications of 2-Arylbenzothiazoles3 Construction of the 2-Arylbenzothiazole Core4 Synthesis 2-Arylbenzothiazoles via Direct C–H Functionalization5 Conclusion

Recent advances in radical-mediated intermolecular (4 + 2) cycloaddition

“…In 2019, Luo, Liu, Xu and coworkers described a highly efficient synthesis of 1,4-dihydroquinolines through the intermolecular (4 + 2) radical cycloaddition of N -methylanilines and alkynoates in a catalyst-free system (Scheme 18a). 30 The control experiment of N , N -dimethylaniline with TMSCN under the standard conditions gave a trace amount of the target product 60 , suggesting that the iminium ion AA was not the possible intermediate (Scheme 18). The possible mechanism is that in the presence of DCP, substrate 55 produces α-aminoalkyl radical AB by a SET and a proton transfer.…”

A hybrid Au/Ru catalyst for sequential alkyne hydration/asymmetric transfer hydrogenation reactions

“…In another study, in 2020, Luo and colleagues used a Tang catalyst based on formic acid/iridium to catalyze sequential reactions of alkyne hydration/transfer hydrogenation. 10 Regarding the earlier study demonstrated by Xiao et al , 8 only a five-fold excess of formic acid relative to alkyne was used at 80 °C to obtain the hydration product. In addition to acid-based sequential AH/ATH reactions, binary homogeneous catalyst systems including Au/Ru, Au/Rh, and Co/Ru were employed to produce alcohols from alkynes.…”

Iron(III)-Catalyzed Regioselective Synthesis of Electron-Rich Benzothiazoles from Aryl Isothiocyanates via C–H Functionalization

“…Further, some of the salient 2-arylbenzothiazole derivatives have been studied in the context of organic luminophoric materials . To date, only a handful of synthetic protocols have been reported for the synthesis of benzothiazoles including the conventional condensation of o -aminothiophenols and carboxylic acids, cross-coupling (Scheme a), C–H functionalization (Scheme b), direct arylation of benzothiazoles (Scheme c), and thiolation of imines (Scheme d) . In this context, Lei et al 11c and Sutherland et al 11e developed iron­(III)-catalyzed synthetic routes for preparing substituted benzothiazoles via C–H functionalization/C–S bond formation (Scheme b).…”