Enantioselective La<sup>III</sup>-pyBOX-Catalyzed Nitro-Michael Addition to (<i>E</i>)-2-Azachalcones
作者:Gonzalo Blay、Celia Incerti、M. Carmen Muñoz、José R. Pedro
DOI:10.1002/ejoc.201201579
日期:2013.3
[La(OTf)3] complex with a new pyBOX ligand bearing a bulky 1-naphthylmethyl substituent at the 4′-position of the oxazoline ring catalyzes the conjugate addition of nitroalkanes to a broad range of (E)-2-azachalcones, providing the expected nitro-Michael products with good yields and enantiomeric excesses up to 87 %. The optical purity of the products can be increased by a single crystallization. A plausible
Bifunctional chiralsquaramide-catalyzedhighlyenantioselectiveMichaeladdition of nitromethane to diverse 2-enoylazaarenes was successfully performed. This protocol provided a set of chiral azaarene-containing γ-nitroketones with up to 98% yield and 98% ee in a solvent-free catalytic system under mild conditions. Furthermore, gram-scale synthetic utility was also showcased.