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

Abstract

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. Both NaI-HI and TFA-Ac2O systems control the selective C−S bond cleavage and...

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

“…Based on previous works and our control experiments, ,– ,– a plausible mechanism for the NBS-mediated C­(sp 3 )–S bond cleavage process of furfuryl and benzyl alkylthioethers was proposed in Scheme a. It is believed that the reaction between thioether 1 and NBS generates transient bromosulfonium salt A , which can subsequently be converted to carbocation B and sulfenyl bromide C .…”

“…The selective C–S bond cleavage of thioethers has received a great deal of attention due to its broad beneficial effects in organic and pharmaceutical chemistry. – Among these fields, most of the previous examples typically used transition-metal catalysts to achieve selective C–S bond cleavage and subsequent transformations (Figure b). While these methods are effective, there are still some inherent limitations, such as (a) the relatively stable metal–sulfur bonds can easily lead to catalyst deactivation; (b) the selectivity of C­(sp 2 )–S bond is much better than C­(sp 3 )–S bond in transition-metal catalysis; and (c) transition-metal residues limit their use in pharmaceutical chemistry. – …”

“…In recent years, metal-free C–S bond cleavage of thioethers has been achieved by using halogenated reagents, peroxides, and bases. – Moreover, organic photochemical strategies have also been reported to realize this process. – Very recently, Lei and co-workers first demonstrated a metal-free organic electrochemical strategy to achieve selective C­(sp 3 )–S bond cleavage of unsymmetrical dialkyl thioethers (Figure c) . However, this method could not be used to obtain the desired products for the researcher without an electrochemical instrument.…”

Substrate‐controlled chemoselective synthesis of 1‐sulfonylquinazoline‐2,4(1H,3H)‐diones and 2‐sulfonamidobenzonitriles

“…In 2022, Sun and co-workers [6] reported the establishment of diverse transformations of 2-alkylthioben zamides and the synthesis of 2,3-dihydrobenzothiazin-4-ones, benzoisothiazol-3-ones, and 2-alkylthiobenzon itriles under the presence of selectfluor (Scheme 1, eqn. a).…”

Metal-free three-component tandem cyclization for modular synthesis of 2,3-dihydrobenzothiazin-4-ones

“…9 Later on, Sun's research group disclosed an excellent Selectfluor-mediated diverse transformation of 2-alkylthiobenzamides via selective C–S bond cleavage and C–H bond functionalization, in which Selectfluor was first used as a methylene source to assemble 2,3-dihydrobenzothiazinones (Scheme 1B). 10 In spite of these remarkable advances to access 2,3-dihydrobenzothiazinones, the known approaches still have several limitations, such as harsh reaction conditions, involvement of metal reagents, need for oxidants, high reaction temperature and so on. On the basis of retrosynthetic analysis, 2,3-dihydrobenzothiazinones could be dissected into three components: a sulfur-containing section, a carbon-bearing fraction and a nitrogenous fraction (Scheme 1C).…”