Divergent Construction of Benzothiophene-Fused N‑Heterocycles via Stereotunable Three-Component Domino Reactions

A stereotunable three-component domino
strategy among thioisatin,
2-bromo-1-phenylethan-1-one, and cyclohexane-1,2-diamine under catalyst-free
conditions was disclosed. A wide range of benzothiophene-fused polycycles
and eight-membered N-heterocycles were synthesized by regulating the
stereoconfiguration of cyclohexane-1,2-diamines. The detailed mechanism
and the origin of the chemoselectivity were explored by density functional
calculations. Analysis of the geometrical structures of key transition
states revealed that the existence of favorable intramolecular attractions,
and the steric effect governed the chemoselectivity observed.