Rapid and Chemodivergent Synthesis of N‑Heterocyclic Sulfones and Sulfides: Mechanistic and Computational Details of the Persulfate-Initiated Catalysis

N-Heterocyclic sulfones
and sulfides are key functional motifs
in medicinal and agricultural chemistry and important building blocks
in organic synthesis. Currently available methods produce N-heterocyclic
sulfones in low yields and under harsh conditions. Here, we describe
a rapid sulfone synthesis under ambient conditions that is initiated
by persulfate with water as a cosolvent. The reaction has a broad
scope and is readily expanded to the chemodivergent synthesis of symmetrical
N-heterocyclic sulfones and sulfides. The products can be isolated
by simple filtration. Our combined experimental and computational
study suggests that the remarkable persulfate-initiated acceleration
of the sulfone formation in the biphasic system that enables the otherwise
sluggish reaction under ambient conditions is due to the combination
of the previously unknown rapid acidification of the persulfate–sulfinate
system, the self-catalysis of the reaction of sulfinic acid with halo-N-heterocycles,
and the substantial acceleration of the reaction in the aqueous phase.