title: Binap and Phosphoramidites as Privileged Chiral Ligands for the Metal-Catalyzed Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylides.
abstract: 2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl (binap) and phosphoramidites are privileged chiral ligands that have been tested in the coinage-metal-catalyzed 1,3-dipolar cycloadditions of metalloazomethine ylides and electrophilic alkenes. Silver(I), copper(II), and gold(I) salts have been evaluated in all of these reactions. Maleimides, acrylates, fumarates, 1,2-bis(phenylsulfonyl)ethylene, and enones reacted with imino esters to give the corresponding endo-prolinates, such as hepatitis C (HCV) inhibitors, in high diastereo- and enantioselectivity using either binap-silver and -gold(I) or phosphoramidite-silver complexes. In the case of nitroalkenes, exo-4-nitroprolinates were obtained using silver or copper(II) phosphoramidite complexes. Azlactones reacted with maleimides and acrylates to give pyrrolines only in the presence of binap-gold(I) complexes. The observed enantioselectivity and mechanism of these 1,3-dipolar cycloadditions were studied for the most relevant examples by means of DFT calculations.
authors.affiliation: Department of Organic Chemistry and Centro de Innovación, en Química Avanzada (ORFEO-CINQA)Faculty of Sciences, University of Alicante, 03080, Alicante, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Nájera
authors.affiliation: Department of Organic Chemistry, Instituto de Síntesis Orgánica, and Centro de Innovación en Química Avanzada (ORFEO-CINQA)Faculty of Sciences, University of Alicante, 03080, Alicante (Spain).
authors.forename: José M
authors.initials: JM
authors.lastname: Sansano
keywords: asymmetric catalysis; cycloaddition; enantioselectivity; ligand design; transition metals