Synthesis and characterization of some new c2 symmetric chiral bisamide ligands derived from chiral feist's acid

Abstract

The hemilabile chiral C 2 symmetrical bidentate substituted amide ligands (1R,2R)-5 a-d and (1S,2S)-6 a-d were synthesized in quantitative yield from (1R,2R)-(+)-3- methylenecyclo-propane-1,2-dicarboxylic acid (1R,2R)-3 and (1S,2S)-(-)-3-methylenecyclopropane- 1,2-dicarboxylic acid (1S,2S)-3, in two steps, respectively. The chiral Feist's acids (1R,2R)-3 and (1S,2S)-3 were obtained in good isomeric purity by resolution of trans-(±)-3-methylene-cyclopropane-1,2-dicarboxylic acid from an 8:2 mixture of tert-butanol and water, using (R)-(+)-α-methylbenzyl amine as a chiral reagent. This process is reproducible on a large scale. All these new synthesized chiral ligands were characterized by 1H-NMR, 13C-NMR, IR, and mass spectrometry, as well as elemental analysis and their specific rotations were measured. These new classes of C 2 symmetric chiral bisamide ligands could be of special interest in asymmetric transformations. © 2012 by the authors.