Zn(II)-Catalyzed Asymmetric Reactions of Aminocyclopropanes: (3 + 2) Cycloaddition with Thioketones and Ring Opening with Thioureas

Using C₁-symmetric imidazolidine-pyrroloimidazolone-pyridine as a ligand and Zn(OTf)₂ as a Lewis acid, an asymmetric (3 + 2)-cyclization reaction of donor-acceptor aminocyclopropanes and thioketones was carried out, providing tetrahydrothiophene derivatives in up to 99% yield, with up to >20:1 dr and 87-99% ee. Additionally, an asymmetric ring opening reaction between aminocyclopropane and substituted thioureas yielded sulfur-containing acyclic compounds with up to 99% yield and up to 96% ee. Furthermore, the origin of the high stereoselectivity was elucidated by control experiments and X-ray crystallography of the chiral Zn(OTf)₂-ligand complex.