An operationally simple and efficient one-pot protocol for the synthesis of highly functionalized thiazolidin-4ones and thiazolines has been devised via Rh(OAc) 2 -catalyzed annulative coupling of β-ketothioamides with diazo compounds under mild reaction conditions for the first time. This double functionalization of diazo compounds proceeds via selective Salkylation followed by intramolecular N-cyclization enabling the formation of C−S and C−N bonds at moderate temperature. Notably, the products possess Z-stereochemistry with regard to the exocyclic CC double bond at the 2-position of the ring. Further, the synthetic utility of the strategy has been revealed to access 2,3-dihydrobenzo[d]thiazoles. Remarkably, atom economy and tolerance of a wide range of functional groups are added characteristics to this strategy.

A photocatalyst‐ and additive‐free, visible‐light‐mediated chemoselective domino protocol was devised to access fully substituted thiazoline derivatives from β‐ketothioamides and α‐diazo 1,3‐diketones at moderate temperature in open air. The reaction proceeds through in situ generation of electrophilic carbenes from α‐diazo 1,3‐diketones by a low‐energy blue LED (448 nm), which undergoes selective coupling with nucleophilic β‐ketothioamides to give thiazolines by successive formation of C−S and C−N bonds in one stretch. Notably, the benign and clean conditions, operational simplicity, sustainability, 100 % carbon economy, high yields, and wide functional‐group tolerance are further attributes of the strategy. A mechanistic rationale for this cascade reaction sequence is well supported by control experiments.

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.

An efficient chemoselective practical route to fully substituted thiazoles and 2,3-dihydrothiazoles has been devised by [4 + 1] heterocyclization of α-(N-hydroxy/aryl)imino-β-oxodithioesters with in situ generated Cu-carbenoids of diazocarbonyls. The α-(N-hydroxy/aryl)imino-β-oxodithioesters are readily accessible by the reaction of β-oxodithioesters with nitrous acid/nitrosoarenes. The overall transformation involves sequential N-O/C-N bonds cleavage followed by cascade C-N/C-S bonds formation in one-pot. This new strategy allows full control over the introduction of various sensitive functional groups at different positions of the thiazole ring, broadening the arsenal of synthetic methods to obtain such scaffolds.

Phosphonium ylides are being reported here as a catalyst for the formation of thiazolidines and 1,3-thiazinanes from β-ketothioamides with dihaloalkanes via [3 + 2] and [3 + 3] annulations under metal-free conditions.