Access to Functionalized Thiazolothiadiazoles via the Chemoselective Cascade Heteroannulation of Thioamides with Hypervalent Iodine Reagents.

We describe herein a chemo- and regioselective cascade annulation between β-ketothioamides and diazo-substituted hypervalent iodine reagents under transition-metal-free and base-free conditions at room temperature. Thus, a divergent construction of fused-heterocyclic scaffold thiazolothiadiazoles has been achieved with the advantages of operational simplicity, scalability, broad substrate compatibility, and mild reaction conditions. This one-pot strategy not only avoids potential toxicity but also broadens the arsenal of synthetic methods to obtain fused N , S -heterocyclic frameworks.