Copper-Mediated Tandem C(sp2)-H Sulfenylation and Annulation of Arenes with 2-Mercaptoimidazoles: Regio- and Site-selective Access to Polycyclic Fused Imidazo[2,1-b][1,3]thiazinones

An efficient copper-mediated tandem C(sp(2))-H sulfenylation and annulation of arenes with 2-mercaptoimidazoles to provide polycyclic fused imidazo[2,1-b][1,3]thiazinones has been developed. This tandem reaction is likely initiated by C(sp(2))-H thiolation of benzamide with 2-mercaptoimidazole followed by intramolecular nucleophilic substitution of the amide carbonyl group. A notable feature of this reaction is that it can afford rather complex products in a single synthesis step from easily accessible starting materials using amide-oxazoline as a removable bidentate directing group. A variety of benzamides and 2-mercaptoimidazoles bearing different substituents are compatible with this transformation.