An umpolung N-alkylation reaction of α-cyclopropyl α-iminothioesters with diethylaluminum chloride or ethylmagnesiumbromide affords the corresponding N-ethylated α-aminothioesters in good yields. Subsequent oxidation and reaction of the N-ethylated product with a thiolate or a chloride anion proceed effectively to give the ring-opened products in good yields. In contrast, relatively “hard” nucleophiles