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- Title
Enantioselective Henry and Aza-Henry Reaction in the Synthesis of ( R)-Tembamide Using Efficient, Recyclable Polymeric Cu<sup>II</sup> Complexes as Catalyst.
- Authors
Das, Anjan; Choudhary, Manoj K.; Kureshy, Rukhsana I.; Roy, Tamal; Khan, Noor‐ul H.; Abdi, Sayed H. R.; Bajaj, Hari C.
- Abstract
Chiral copper(II) polymeric [H4]salen (salen=bis[(salicylidene)ethylenediaminato]) complexes CuII-1- 3 were generated in situ and used as efficient catalysts in the asymmetric Henry and aza-Henry reaction of various aromatic and aliphatic aldehydes and N-tosylimines in the presence of various nitroalkanes at room temperature (27±2 °C) for 20 hours. This group of polymeric [H4]salen complexes demonstrated excellent performance (product yield and enantiomeric excess ee up to 98 %) in the formation of β-nitroalcohol by using nitromethane with low catalyst loading of 1 mol % (with respect to the monomeric salen unit) and high enantioinduction ( ee 94 %) in the aza-Henry product; β-nitroamines were obtained with moderate yield (78 %). This catalytic system also worked well with nitroethane and 1-nitropropane in the case of Henry reaction, to furnish the corresponding products in high yields and enantioselectivities for syn diastereomers. The CuII-2 complex retained its performance at the gram level and was expediently recycled eight times with no significant loss in its performance. The kinetic study with CuII-2 complex for the enantioselective aza-Henry reaction of N-Ts-benzylimine (Ts=tosyl) revealed a first-order dependence on catalyst and nitromethane concentration and was zero order with respect to the substrate. The product obtained was transformed straightforwardly to the pharmaceutically important enantiomerically pure ( R) -tembamide (β-adrenergic agonist) drug in good yield by the asymmetric nitroaldol reaction of 4-methoxybenzaldehyde in three successive steps.
- Subjects
NITROALDOL reactions; ASYMMETRIC synthesis; ENANTIOSELECTIVE catalysis; ALKALOID synthesis; COPPER compounds; LIGANDS (Chemistry)
- Publication
ChemPlusChem, 2014, Vol 79, Issue 8, p1138
- ISSN
2192-6506
- Publication type
Article
- DOI
10.1002/cplu.201402078