Synthesis and Structural Characterization of Planar Chiral Cr(CO)3‐Complexed Aromatic Nitrones – Valuable Substrates for Asymmetric SmI2‐Induced Coupling Reactions

Abstract

AbstractThe synthesis of Cr(CO)3‐complexed aromatic nitrones 2 is reported. These new planar‐chiral complexes were fully characterized in solution by 1H and 13C NMR, IR and cyclic voltammetry. Moreover, structural data were obtained from X‐ray structures of nitrones 2b, 2d, 2e and 2f. These analyses converge to give evidence of a favoured anti conformation of ortho‐substituted nitrones, with an unusual N–O···Haryl intramolecular interaction forming a six‐membered ring. The reactivity of these chiral nitrones in SmI2‐induced pinacol‐type reactions was investigated. The reductive cross‐coupling of nitrones 2a–d with carbonyl compounds proved to be highly chemo‐ and diastereoselective and afforded precursors of enantioenriched β‐amino alcohols in excellent yields.