Design, synthesis and application of chiral tetraoxacalix[2]arene[2]triazine-based organocatalysts in asymmetric Michael addition reactions

A novel type of oxacalix[2]arene[2]triazine-based organocatalysts for asymmetric Michael reactions are reported for the first time. Chiral subunits were attached to the heteroatom-bridged calixaromatic platform by a reaction of (R)- and (S)-1-aminotetraline with tetraoxacalix[2]arene[2]triazine in both enantiomeric forms. To evaluate the catalytic efficiency of the novel organocatalysts, isobutyraldehyde reacted with various substituted and unsubstituted aromatic trans-beta-nitrostyrenes in tetrahydrofuran (THF), leading to Michael adducts in excellent yields and enantioselectivites (up to 97% yield and 99% ee).