Stereoselective Synthesis Of β-diaryl Amino Acids

The reaction involving azomethine ylides is an important 1.3-dipol for the synthesis of nitrogen-containing compounds.Most of the reactions are concentrated in the [3+2] cycloaddition reaction of azomethine ylides with electron-deficient olefins or alkynes to form tetrahydropyrrolidines.Since 1999,the Pedregal group was first to report the addition of azomethine ylides with the electron-deficient olefins to produce an amino acid compound.The addition reaction of azomethine ylide is an important way to introduce different substituents into the amino acid molecule.A fully stereoselective synthesis of unnatural chiral β-bis-aryl-α-amino acid esters via copper-catalyzed addition reactions of azomethine ylides with benzylidenepyrazolones bearing two contiguous stereo-genic centers was developed.A 1H-pyrazol-5-ol was introduced by the aromatization of 3H-pyrazol-3-one in the reaction.The transformation operated at room temperature and afforded β-1H-pyrazol-5-ol-α-amino esters in high yields with good to excellent levels of enantioselectivity.