Asymmetric synthesis of anti- and syn-beta-amino alcohols by reductive cross-coupling of transition metal-coordinated planar chiral arylaldehydes with aldimines

Samarium iodide-mediated cross-coupling of N-tosyl ferrocenylideneamine with planar chiral ferrocenecarboxaldehydes or benzaldehyde chromium complexes gave diastereoselectively the corresponding anti-beta-amino alcohol derivatives in good yields, while N-tosyl benzylideneamine produced syn-beta-amino alcohols by coupling with planar chiral arylaldehydes. Dynamic kinetic resolution of a configurationally equilibrated reactive species generated from achiral N-tosyl ferrocenilideneamine and benzylideneamine by reduction with samarium iodide was observed in the cross-coupling with planar chiral arylaldehydes giving both antipodes of beta-amino alcohols depending on the planar chirality. The obtained anti-beta-amino alcohol with the ferrocene ring was utilized as a chiral ligand for catalytic asymmetric reduction of acetophenone.