1.Enantioselective 1,3-dipolar cycloaddition of azomethine imines with propioloylpyrazoles induced by chiral π-cation catalysts.
Hori M1, Sakakura A, Ishihara K. J Am Chem Soc. 2014 Sep 24;136(38):13198-201. doi: 10.1021/ja508441t. Epub 2014 Sep 16.
We developed 1,3-dipolar cycloadditions of azomethine imines with propioloylpyrazoles catalyzed by a chiral copper(II) complex of 3-(2-naphthyl)-l-alanine amide. The asymmetric environment created by intramolecular π-cation interaction and the N-alkyl group of the chiral ligand gives the corresponding adducts in high yields with excellent enantioselectivity. This is the first successful method for the catalytic enantioselective 1,3-dipolar cycloaddition of azomethine imines with internal alkyne derivatives to give fully substituted pyrazolines.
