A new methodology for the synthesis of Nhaloindole-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.

A chemoselective and metal/additive-free protocol for the synthesis of propargylic cyclic imine derivatives via (3+2)-cycloaddition of donor-acceptor cyclopropanes and alkynylnitriles in the presence of BF3·OEt2 has been established. The newly...