Metal-free direct C(sp3)−H functionalization of 2-alkylthiobenzoic acid to access 1,3-benzooxathiin-4-one

Recent Advances in the Synthesis of Benzo[d]isothiazol-3(2H)-One and Benzo[e][1,3]Thiazin-4-One Derivatives

Benzo[d]isothiazol-3(2H)-one and benzo[e][1,3]thiazin-4-one derivatives, as significant sulfur- and nitrogen-containing heterocyclic compounds, are prevalent in natural products, pharmaceuticals, and food items. In recent years, a variety of innovative synthetic methodologies for these compounds have been developed. In this review, we will comprehensively introduce the major advances in the synthesis of benzo[d]isothiazol-3(2H)-one and benzo[e][1,3]thiazin-4-one derivatives via both intramolecular and intermolecular pathways from 2012 to the present.

Recent Advancement on Selectfluor Mediated Synthesis of Heterocyclic Molecules

Selectfluor, [1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)], is a highly valuable reagent in contemporary chemistry, serving not only as an electrophilic fluorinating agent but also as an effective catalyst in the synthesis of various pharmaceutically relevant heterocycles. This review article seeks to present a comprehensive overview of the significant heterocyclic ring formations facilitated by selectfluor. Both metal-free and metal-catalyzed recent advancement on selectfluor mediated cyclisation processes are discussed in this review mainly over last eight years (2017-April 2024).

Selective C(sp3)-S Bond Cleavage of Thioethers to Build Up Unsymmetrical Disulfides

The selective C(sp3)-S bond cleavage of thioethers was first developed to prepare unsymmetrical disulfides by using electrophilic halogenation reagents. In this strategy, NBS (N-bromosuccinimide) achieves selective furfuryl C(sp3)-S bond cleavage of furfuryl alkylthioethers at room temperature. Meanwhile, NFSI (N-fluorobenzenesulfonimide) enables selective methyl C(sp3)-S bond cleavage of aryl and alkyl methylthioethers at an elevated temperature. Notably, the substrate scope investigation indicates that the order of selectivity of the C-S bond cleavage is furfuryl C(sp3)-S > benzyl C(sp3)-S > alkyl C(sp3)-S > C(sp2)-S bond. Moreover, this practical and operationally simple strategy also provides an important complementary way to access various unsymmetrical disulfides with excellent functional group tolerances and moderate to good yields.

Recent Strategies in Nickel-Catalyzed C–H Bond Functionalization for Nitrogen-Containing Heterocycles

N-heterocycles are ubiquitous in natural products, pharmaceuticals, organic materials, and numerous functional molecules. Among the current synthetic approaches, transition metal-catalyzed C–H functionalization has gained considerable attention in recent years due to its advantages of simplicity, high atomic economy, and the ready availability of starting materials. In the field of N-heterocycle synthesis via C–H functionalization, nickel has been recognized as one of the most important catalysts. In this review, we will introduce nickel-catalyzed intramolecular and intermolecular pathways for N-heterocycle synthesis from 2008 to 2021.

Metal-free and Selectfluor-mediated diverse transformations of 2-alkylthiobenzamides to access 2,3-dihydrobenzothiazin-4-ones, benzoisothiazol-3-ones and 2-alkylthiobenzonitriles

Diverse transformations of 2-alkylthiobenzamides have been established to synthesize 2,3-dihydrobenzothiazin-4-ones, benzoisothiazol-3-ones and 2-alkylthiobenzonitriles in the presence of Selectfluor.

Amide-assisted α-C(sp3)–H acyloxyation of organic sulfides to access α-acyloxy sulfides

The direct acyloxyation of 2-(alkylthio)benzamide has been established via an amide-assisted α-C(sp3)–H functionalization in the presence of Selectfluor by using simple carboxylic acid and its corresponding salt as acyloxy sources.