Enantioselective addition of phenylacetylene to aldehydes catalyzed by silica-immobilized titanium(IV) complex of β-hydroxyamide

A chiral β-hydroxyamide was synthesized from l-phenylalanine and successfully grafted onto amorphous silica gel. The silica-immobilized ligand was characterized by FT-IR, solid state NMR and elemental analysis. This is the first example of asymmetric addition of phenylacetylene to aldehydes catalyzed by silica-immobilized titanium(IV) complex of β-hydroxyamide with high yields (up to 95%) and good enantioselectivities (up to 81% ee). The catalyst could be reused up to five times without serious loss of enantioselectivity.

Graphical abstractA chiral β-hydroxy amide was synthesized from l-phenylalanine and successfully grafted onto amorphous silica gel. Asymmetric addition of phenylacetylene to aldehydes was catalyzed by silica-immobilized titanium(IV) complex of β-hydroxy amides with good enantioselectivities (up to 81% ee). After readily recoverable procedure, the ligand could be reused several times without serious loss of enantioselectivity.Figure optionsDownload full-size imageDownload as PowerPoint slide