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.

Enantioselective Synthesis of Succinimides by Michael Addition of 1,3-Dicarbonyl Compounds to Maleimides Catalyzed by a Chiral Bis(2-aminobenzimidazole) Organocatalyst

A wide variety of chiral succinimides have been prepared in high yields and enantioselectivities by asymmetric conjugate addition of 1,3-dicarbonyl compounds to maleimides under very mild reaction conditions using a bifunctional benzimidazole-derived organocatalyst. Computational and NMR studies support the hydrogen-bonding activation role of the catalyst and the origin of the stereoselectivity of the process.

Liquid–Liquid Equilibria of Water + Ethanol + 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide Ternary System: Measurements and Correlation at Different Temperatures

In this work authors present the experimental liquid–liquid equilibria (LLE) data of water + ethanol + 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([bmim][Tf2N]) system at different temperatures. The LLE of the system was obtained in the temperature range from 283.2 to 323.2 K. The nonrandom two liquid (NRTL) and universal quasichemical (UNIQUAC) models were used to correlate ternary systems. The equilibrium compositions were successfully correlated by the interaction parameters from both models, however UNIQUAC gave a more accurate correlation. Finally, a study about the solvent capability of ionic liquid was made in order to evaluate the possibility of separating the mixture formed by ethanol and water using that ionic liquid.

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.

Microwave-assisted multicomponent diastereoselective 1,3-dipolar cycloaddition of ethyl glyoxylate derived azomethine ylides

The thermal multicomponent 1,3-dipolar cycloaddition (1,3-DC) of diethyl aminomalonate or α-amino esters (derived from glycine, alanine, phenylalanine, and phenylglycine) with ethyl glyoxylate and the corresponding dipolarophile such as maleimides, methyl acrylate, methyl fumarate, (E)-1,2-bis(phenylsulfonyl)ethylene, and electron deficient alkynes allows the diastereoselective synthesis of new polysubstituted pyrrolidine derivatives. Microwave-assisted heating processes give better results than conventional heating ones, affording endo-cycloadducts as major stereoisomers. In general, 2,5-cis-cycloadducts are preferentially formed according to the previous formation of the W-shaped dipole. Only in the 1,3-DC of the disulfone with phenylglycine and ethyl glyoxylate the corresponding exo-trans-cycloadduct was isolated. The compound endo-cis-4b, derived from phenylalanine, ethyl glyoxylate and N-benzylmaleimide, has been further transformed into a very complex diazabicyclo[2.2.1]octane skeleton with potential biological activity.