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

Direct Synthesis of Benzothiazoles and Benzoxazoles from Carboxylic Acids Utilizing (o-CF3PhO)3P as a Coupling Reagent

A general and efficient method for the direct synthesis of benzothiazoles and benzoxazoles from carboxylic acids with 2-aminobenzenethiols or 2-aminophenols using (o-CF3PhO)3P as a simple coupling reagent has been developed. Diverse benzothiazoles and benzoxazoles were synthesized in moderate to excellent yields. And the gram-scale preparation of benzothiazole and benzoxazole also proceeded smoothly under the mild conditions. Moreover, a plausible reaction mechanism was discussed, with (o-CF3PhO)3P and its hydrolysis product (o-CF3PhO)2P(O)H contributing to the formation of the target products as an amide synthesis coupling agent and a cyclization reaction promoter, respectively.

Isothiocyanates: happy-go-lucky reagents in organic synthesis

Owing to their unique structural features, isothiocyanates (ITCs) are a class of highly useful and inimitable reagents as the -NCS group serves both as electrophile and nucleophile in organic synthesis. ITCs share a rich legacy in organic, medicinal, and combinatorial chemistry. Compared to their oxygen equivalents, isocyanates, ITCs are easily available, less unpleasant, and somewhat less harmful to work with (mild conditions) which makes them happy-go-lucky reagents. Functionalized ITCs can finely tune the reactivity of the -NCS group and thus can be exploited in the late-stage functionalization processes. This review's primary aim is to outline ITC chemistry in the construction and derivatization of heterocycles through the lens of sustainability. For ease and brevity, the sections are divided based on reactive centers present in functionalized ITCs and modes of cyclisation. Scrutinizing their probable unexplored directions for future research studies is also addressed.