Synthesis of Indole-Fused Dihydrothiopyrano Scaffolds via (3+3)- Annulations of Donor-Acceptor Cyclopropanes with Indoline-2-Thiones

A new methodology for the synthesis of N-haloindole-fused dihydrothiopyrano derivatives via (3 + 3) -annulation of donor-acceptor cyclopropanes (DACs) with indoline-2-thiones in the presence of Sc(OTf)3 as a Lewis acid catalyst has been developed. This protocol provides a variety of indole-fused dihydrothiopyrano molecules in good to excellent yields, which architecturally resemble other indole-fused tricyclic molecules having potential medicinal value. In addition, we have described a detailed reaction mechanism and transformation of the furnished product into N-fused thiazino indole molecule.

Automated summary

A new methodology for the synthesis of N-haloindole-fused dihydrothiopyrano derivatives has been developed via (3 + 3) -annulation of donor-acceptor cyclopropanes with indoline-2-thiones in the presence of Sc(OTf)3 as a Lewis acid catalyst. This protocol provides a variety of indole-fused dihydrothiopyrano molecules in good to excellent yields, which resemble other indole-fused tricyclic molecules with potential medicinal value. Additionally, a detailed reaction mechanism and transformation of the product into N-fused thiazino indole molecule have been described.