Rhodium(II)-Catalyzed Annulative Coupling of β-Ketothioamides with α-Diazo Compounds: Access to Highly Functionalized Thiazolidin-4-ones and Thiazolines

An operationally simple and efficient one-pot protocol for the synthesis of highly functionalized thiazolidin-4-ones 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 S-alkylation 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.