FeCl3-Promoted [3+2] Annulations of γ-Butyrolactone Fused Cyclopropanes with Heterocumulenes

The [3 + 2] annulations of gamma-butyrolactone fused donor acceptor (D-A) cyclopropanes with aromatic isothiocyanates and dialkyl carbodiimides promoted by FeCl3 is reported. A series of bicyclic/polycyclic gamma-butyrolactone fused thioimidates and gamma-butyrolactone fused amidines containing four contiguous stereogenic centers were obtained in excellent yields as single stereoisomers.