Synthesis of 4‐(Trifluoromethyl)‐2,3‐Dihydrothiazoles from α‐Enolic Dithioesters and Imidoyl Sulfoxonium Ylides

Abstract

The synthesis of 4‐(trifluoromethyl)‐2,3‐dihydrothiazoles from α‐enolic dithioesters and imidoyl sulfoxonium ylides has been achieved under thermal conditions. This transformation is catalyst‐free, additive‐free, and operationally simple, and it proceeds via a formal insertion of alkenyl S−H generated in situ from dithioesters into ylides followed by an intramolecular annulation. This approach further expands the synthetic application of two versatile sulfur‐containing building blocks of fluorinated imidoyl sulfoxonium ylides and α‐enolic dithioesters.

Construction of trifluoromethyl-containing heterocycles from trifluoroacetimidoyl chlorides and derivatives

“…A heating-promoted annulation of CF 3 -imidoyl sulfoxonium ylides and α-enolic dithioesters under catalyst- and additive-free conditions was achieved by Cheng, Yang and co-workers, which provided a facile approach for the assembly of 4-(trifluoromethyl)-2,3-dihydrothiazoles (Scheme 50). 63 α-Enolic dithioesters, as a kind of versatile sulfur-containing synthons with several nucleophilic and electrophilic reactive sites, have been utilized to construct various heterocycles. Inspired by Cheng's work involving the reaction of TFISYs with 1,3-dicarbonyl compounds, α-enolic dithioesters with the similar structure reacted with TFISYs under only thermal conditions to yield the unexpected 4-(trifluoromethyl)-2,3-dihydrothiazole products.…”

“…A heating-promoted annulation of CF 3 -imidoyl sulfoxonium ylides and a-enolic dithioesters under catalyst-and additivefree conditions was achieved by Cheng, Yang and co-workers, which provided a facile approach for the assembly of 4-(trifluoromethyl)-2,3-dihydrothiazoles (Scheme 50). 63 isocyanides with sulfoxonium ylides, 64 a heating-induced desulfurization annulation of TFISYs and isothiocyanates for the construction of biologically valuable 2-trifluoromethyl-4aminoquinolines was presented by Wu, Chen and co-workers (Scheme 51). 65 The simple transformation was performed under catalyst-and additive-free conditions, which had many advantages of easy operation, insensitivity to air and moisture, high efficiency and scalibility.…”

A decade update on the application of β-oxodithioesters in heterocyclic synthesis

“…Encouraged by this work, our group recently achieved the synthesis of CF 3 -substituted 2,3-dihydrothiazoles 29-3 through regioselective annulation of α-enolic dithioesters 29-1 with trifluoromethylated imidoyl sulfoxonium ylides 29-2 under metal- and additive-free conditions (Scheme 29). 46 Based on the mechanistic study, we proposed a tandem process involving a formal insertion of alkenyl S–H generated from α-enolic dithioesters into ylides to connect two reactants followed by intramolecular annulation to form thiazole rings.…”

Synthesis of Multifunctionalized Thiazolidine‐4‐thiones via [2+2+1] Annulation of Isothiocyanates and CF3‐Imidoyl Sulfoxonium Ylides

“…Subsequently, Xiong reported a sequence LiBr‐promoted O−H insertion of TFISYs/palladium‐catalyzed annulation reaction for the synthesis of 3‐CF 3 ‐1,4‐benzoxazines [8] . Furthermore, Cheng's group achieved the synthesis of 4‐CF 3 ‐2,3‐dihydrothiazoles from α ‐enolic dithioesters and TFISYs under catalyst‐ and additive‐free conditions [9] . Several CF 3 ‐decorated heterocycles were also prepared from TFISYs by Wu's group [10] .…”