anti-Selective Catalytic Asymmetric Nitroaldol Reaction via a Heterobimetallic Heterogeneous Catalyst

Full details of an anti-selective catalytic asymmetric nitroaldol reaction promoted by a heterobimetallic catalyst comprised of Nd5O(OiPr)13, an amide-based ligand, and NaHMDS (sodium hexamethyldisilazide) are described. A systematic synthesis and evaluation of amide-based ligands led to the identification of optimum ligand 1m, which provided a suitable platform for the Nd/Na heterobimetallic complex. During the catalyst preparation in THF, a heterogeneous mixture developed and centrifugation of the suspension allowed for separation of the precipitate, which contained the active catalyst and which could be stored for at least 1 month without any loss of catalytic performance. The precipitate promoted a nitroaldol (Henry) reaction for a broad range of nitroalkanes and aldehydes under heterogeneous conditions, affording the corresponding 1,2-nitroalkanol in a highly anti-selective (up to anti/syn = >40/1) and enantioselective manner (up to 98% ee). Inductively coupled plasma (ICP) and X-ray fluorescence (XRF) analyses revealed that the precipitate indeed included both neodymium and sodium, which was further supported by high-resolution ESI TOF MS spectrometry.