Indoles usually act as nucleophiles to engage in electrophilic substitution reactions, mainly at C-3 position, due to the n-excessive nature of the indolyl aromatic ring.In the course of our studies on indole-based transformations,[1-5] we accidently found that 3-acyl indoles could react with Grignard reagents in a Michael addition fashion, leading to dearomatization of the indole nucleus.Here we reported a general and mild method for stereoselective synthesis of either trans-or cis-indolines using Grignard reagents, as well as a detailed study for further transformations of the magnesium enolate intermediates with various electrophiles.