<i>anti</i>-Selective Catalytic Asymmetric Nitroaldol Reaction via a Heterobimetallic Heterogeneous Catalyst
2009-09-30T00:00:00Z (GMT) by
Full details of an <i>anti</i>-selective catalytic asymmetric nitroaldol reaction promoted by a heterobimetallic catalyst comprised of Nd<sub>5</sub>O(O<sup><i>i</i></sup>Pr)<sub>13</sub>, 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 <b>1m</b>, 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 <i>anti</i>-selective (up to <i>anti</i>/<i>syn</i> = >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.