Full details of an anti-selective catalytic asymmetric nitroaldol reaction promoted by a heterobimetallic catalyst comprised of Nd(5)O(O(i)Pr)(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.
Direct catalytic asymmetric addition of allylic cyanides to N-diphenylphosphinoyl ketoimines with a bimetallic catalytic system comprising Ph-BPE/[Cu(CH3CN)4]ClO4/LiOAr is described. Intermediary alpha-adducts readily isomerized to afford synthetically useful alpha,beta-unsaturated nitriles bearing an optically active tetrasubstituted carbon. Applicability to aromatic, heteroaromatic, and aliphatic ketoimines exemplifies wide substrate generality. Transformation of the product into densely functionalized material showcases the utility of the present protocol.
Battling the flu: Zanamivir (Relenza) is widely prescribed as an anti‐influenza drug. It contains a vicinal amino alcohol, which is in an anti orientation, and is readily accessed by an anti‐selective catalytic asymmetric nitroaldol (Henry) reaction promoted by a heterobimetallic complex (see scheme; PMB=p‐methoxybenzyl). Additional synthetic manipulation of the nitroaldol product allowed the enantioselective synthesis of zanamivir.
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