Tf₂O/2-Chloropyridine-Triggered Synthesis of Benzo[b]thiophene 1,1-Dioxides from Sulfonium α-Acyl Sulfonylmethylides

Abstract

Triflic anhydride and 2-chloropyridine-comediated tandem activation, intramolecular aromatic electrophilic addition, and 1,2-sulfonyl shift via spirocyclic intermediates of sulfonium α-acyl sulfonylmethylides realize the efficient synthesis of 2-alkyl/arylthiobenzo­[b]­thiophene 1,1-dioxides. The deactivated sulfonyl group determines the site-selectivity of the electrophilic addition via the ipso-attack, while the following S-migration controls the regioselectivity. Some of 2-methylthiobenzo­[b]­thiophene 1,1-dioxides show fluorescence properties in the solid state and in their solutions.

Synthesis of Sulfo(xo)nium Diacylmethylides

“…Sulfo(xo)nium diacylmethylides can be compatible with more harsh reaction conditions and show novel activities, possibly a blessing in disguise. In the recent decade, sulfo(xo)nium diacylmethylides have been proved to give rise to furan derivatives, [23] 3-acyl oxindoles, [24] benzo[b]thiophene 1,1dioxides, [25] vinyl sulfones, [26] and α-acyl sulfones with a halogenated quaternary carbon center [27] and can also be used as alkylating and arylating reagents (Scheme 1b). [28] As a results, the preparation of sulfo(xo)nium diacylmethylides with new synthetic strategies has been gradually described.…”