# Thiol-Free Sulfenylation Redefined: A Single-Atom Transfer Pathway to Symmetrical Di(hetero)arylthioethers via B(C6F5)3 Catalysis

## TL;DR

A new method uses a stable reagent and a metal-free catalyst to efficiently make symmetrical thioethers, avoiding traditional problems like odor and instability.

## Contribution

Introduces a metal-free, single-atom transfer pathway using B(C6F5)3 catalysis and N,N′-thiobisphthalimide for symmetrical thioether synthesis.

## Key findings

- N,N′-thiobisphthalimide enables high-yield synthesis of symmetrical thioethers up to 97%.
- Mechanistic studies reveal a stepwise ionic pathway supported by DFT and electrochemical data.
- Resulting thioethers show ambipolar redox behavior, useful for photoredox mediation.

## Abstract

Diarylated thioethers are privileged scaffolds found
across pharmaceuticals,
functional materials, and molecular electronics. Conventional approaches
to these motifs, typically via C–H functionalization or C–X
cross-coupling with thiophenols, disulfides, thiosulfonates, and related
sulfenylating agents, remain hampered by foul odors, instability,
air- and moisture- sensitivity, tedious synthesis, and poor selectivity,
often producing undesired byproducts. In contrast, the few strategies
that employ elemental sulfur for symmetrical thioether synthesis are
largely confined to copper catalysis and lack generality. Therefore,
a straightforward and sustainable route to symmetrical thioethers
from readily accessible, bench-stable sulfenylating agents with broad
substrate compatibility is highly desirable. Herein, we demonstrate N,N′-thiobisphthalimide as a bench-stable
sulfenylating reagent enabling the synthesis of symmetrical diaryl/diheteroaryl
thioethers or dibenzothiophenes in yields up to 97%. This transformation
precedes via a single-atom transfer (SAT) strategy under metal-free
B­(C6F5)3 catalysis with electron-rich
arene and heteroarene substrates. Mechanistic investigations, supported
by DFT calculations, cyclic voltammetry (CV), and UV–vis. studies,
reveal a stepwise ionic pathway and rationalize the observed regioselectivity
and substrate-dependent reactivity. Beyond synthetic value, the ambipolar
redox behavior of the resulting thioethers establishes them as tunable
photoredox mediators, bridging small-molecule synthesis and functional
material design.