Synthesis and Functionalization of Thiazolo[c]isothiazoles

The chalcogen bonding ability of sulfur-containing rings has become a useful development tool in organic chemistry. The explored chemical space of fused thiazoles and isothiazoles is mostly limited to fusions with six-membered rings. Examples of 5,5-fused heteroaromatic scaffolds with multiple sulfur atoms are mostly limited to thiophene rings. This work describes the synthesis and broad functionalizability of building blocks for both thiazolo[5,4-c]isothiazoles and thiazolo[4,5-c]isothiazoles, including selective arylation and substitution. Their hydrogen and chalcogen bonding abilities are demonstrated.