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.