The reaction of chiral imines, derived from aromatic aldehydes and (S)-valinol, with a Grignard reagent in the presence of Mg(0) afforded imino-pinacol coupling products instead of alkylated amines, with a high level of diastereoselectivity. The chiral auxiliary in the product was successfully removed via dehydration followed by hydrolysis, and the corresponding (R,R)-ethylenediamine derivative was obtained as the N-Boc protected form.

Diastereoselective Imino-Pinacol Coupling of Chiral Imines Promoted by Mg(0) and a Grignard Reagent. -In the presence of Mg(0) the Grignard reagent-promoted imino-pinacol coupling of chiral (S)-valinol-derived imines diastereoselectively furnishes ethylenediamine derivatives. -(KITAJIMA, K.; NAGATOMO, R.; FUJIMOTO*, T.; Tetrahedron 71 (2015) 6, 977-981, http://dx.