Visible-Light-Mediated Synthesis of 1,2,4-Dithiazolidines from β‑Ketothioamides through a Hydrogen-Atom-Transfer Photocatalytic Approach of Eosin Y

An efficient protocol for visible-light-mediated
synthesis of a
specific class of 1,2,4-dithiazolidines from β-ketothioamides
is devised employing eosin Y as a photoinitiator at ambient temperature
in an open pot. The reaction proceeds via an in situ-generated thiyl
radical followed by dimerization/deaminative cyclization cascade,
enabling the creation of a dithiazolidine ring through successive
formation of S–S and N–C bonds under metal- and additive-free
conditions. Remarkably, the benign conditions, sustainability, and
quantifying forbearance of wide horizons of functional groups are
added characteristics to the strategy. The developed hydrogen-atom-transfer
methodology will be helpful in postsynthetic modification via added
synthetic handles.