Synthesis of C₃-symmetric tris(β-hydroxy amide) ligands and their Ti(IV) complex-catalyzed enantioselective alkynylation of aldehydes

(Chemical Equation Presented) A series of new chiral C₃- symmetric tris(β-hydroxy amide) ligands have been synthesized via the reaction of 1,3,5-benzenetricarboxylic chloride and optically pure amino alcohols (up to 96% yield). The asymmetric catalytic alkynylation of aldehydes with these new C₃-symmetric chiral tris(β-hydroxy amide) ligands and Ti (OⁱPr)₄ was investigated. Ligand 4c synthesized from (1R,2S)-(-)-2-amino-1,2-diphenylethanol is effective for the enantioselective alkynylation of various aldehydes, and high enantioselectivity was obtained with aromatic aldehydes and α,β-unsaturated aldehyde (up to 92% ee).