Binap and Phosphoramidites as Privileged Chiral Ligands for the Metal-Catalyzed Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylides

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.Our work has been supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) (CTQ2004-00808/BQU, Consolider INGENIO 2010 CSD2007-00006, CTQ2007-62771/BQU, CTQ2010-20387 and the Hispano-Brazilian project PHB2008-0037-PC), the Spanish Ministerio de Economia y Competitividad (MINECO) (projects CTQ2013-43446-P and CTQ2014-51912-REDC) FEDER, Generalitat Valenciana (PROMETEO/2009/039, and PROMETEOII/2014/017), and by the University of Alicante

Binap-gold (I) versus Binap-silver trifluoroacetate complexes as catalysts in 1,3-dipolar cycloadditions of axomethine ylides

The 1,3-dipolar cycloaddition between azomethine ylides and alkenes is efficiently catalysed by [{(Sa)-Binap-Au(tfa)}2] (Binap=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl; tfa=trifluoroacetyl). Maleimides, 1,2-bis(phenylsulfonyl)ethylene, chalcone and nitrostyrene were suitable dipolarophiles even when using sterically hindered 1,3-dipole precursors. The results obtained in these transformations improve the analogous ones obtained in the same reactions catalysed by [Binap–Ag(tfa)]. In addition, computational studies have also been carried out to demonstrate both the high enantioselectivity exhibited by the chiral gold(I) complex, and the non-linear effect observed in this transformation.This work has been supported by the DGES of the Spanish Ministerio de Ciencia e Innovación (MICINN) (Consolider Ingenio 2010 CSD2007-00006, FEDER-CTQ2007-62771/BQU, CTQ2007/67528, CTQ2010-20387 and by the Hispano-Brazilian project PHB2008-0037-PC), Generalitat Valenciana (PROMETEO/2009/039), the Basque government (grant IT-324-07) and by the University of Alicante

Synthesis of prolines by enantioselective 1,3-dipolar cycloaddition of azomethine ylides and alkenes catalyzed by chiral phosphoramidite-silver(I) complexes

The endo-diastereo- and enantioselective 1,3-dipolar cycloaddition of azomethine ylides and electrophilic alkenes is efficiently catalysed by chiral phosphoramidite-silver(I) perchlorate complexes. The reaction allows the presence of different types of substituents in the 1,3-dipole and can be applied to the synthesis of enantiomerically enriched, highly substituted prolines. This methodology was applied to the total synthesis of the inhibitors of the hepatitis C virus (HCV). Computational studies support a two-step mechanism predicting exactly the experimental results and the origin of both the diastereo- and enantioselections, as well as a reasonable explanation concerning the different reaction rates observed for some substrates.This work was supported by the DGES of the Spanish Ministerio de Educación y Ciencia (MEC) (Consolider INGENIO 2010 CSD2007-00006, CTQ2007-62771/BQU and CTQ2004-00808/BQU) and by the University of Alicante

Binap-silver salts as chiral-catalysts for the enantioselective 1,3-dipolar cycloaddition of azomethine ylides and alkenes

Binap-AgSbF6 catalyzed 1,3-dipolar cycloadditions between azomethine ylides and electrophilic alkenes are described and compared with analogous transformations mediated by other Binap-silver(I) salt complexes. Maleimides and 1,2-bis(phenylsulfonyl)ethylene are suitable dipolarophiles for obtaining very good enantioselectivities, even better values are generated by a multicomponent version. There are some very interesting applications of the disulfonylated cycloadducts in the total synthesis of cis-2,5-disubstituted pyrrolidines, precursors of natural products, or valuable intermediates in the synthesis of antiviral compounds.This work has been supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) through the Hispano-Brazilian project PHB2008-0037-PC and CNPq-2878, Consolider INGENIO 2010 CSD2007-00006, CTQ2010-20387, FEDER, Generalitat Valenciana (PROMETEO/2009/039), and by the University of Alicante. MM-R thanks MEC for a predoctoral fellowship. EC thanks CNPq for a predoctoral Doutorado Sanduíche stay

1,3-Dipolar cycloadditions: applications to the synthesis of antiviral agents

In the present perspective the advances and real possibilities of 1,3-dipolar cycloadditions as key steps in the total synthesis of virus inhibitors are described. Azides, nitrones, and azomethine ylides are the most appropriate 1,3-dipoles for the synthesis of privileged structures with the highest biological responses against viruses.This work has been supported by the DGES of the Spanish Ministerio de Educación y Ciencia (MEC) (Consolider INGENIO 2010 CSD2007-00006, CTQ2007-62771/BQU, and CTQ2004-00808/BQU), and by the University of Alicante