A mild and chemoselective three-component
thioesterification using
olefins, α-ketoacids, and elemental sulfur has been developed.
The photocatalytic activation of elemental sulfur, a cheap and abundant
sulfur source, enables the rapid installation of a sulfur atom into
molecules, reactions that ordinarily would require the use of reactive
and malodorous sulfur-containing compounds such as thiols and thioacids.
This novel reaction is characterized by high yields and a broad substrate
scope, which enables the introduction of thioester moieties into complex
molecules including a steroid, a peptide, and a nonprotected glycoside.
Mechanistic studies indicated that the success of this transformation
depends on the multiple roles played by the elemental sulfur, including
those of a sulfurizing agent, a terminal oxidant, and a HAT mediator.