Organometallic titanocene complex as highly efficient bifunctional catalyst for intramolecular Mannich reaction

Article abstract of DOI:10.1002/aoc.4925

Bifunctional catalysts bearing two catalytic sites, Lewis acidic organometallic titanocene and Br?nsted acidic COOH, have been assembled in situ from Cp₂TiCl₂ with carboxylic acid ligands, showing high catalytic activity over an intramolecular Mannich reaction towards synthesis of 2-aryl-2,3-dihydroquinolin-4(1H)-ones. The determination of the bifunctional catalyst Cp₂Ti(C₈H₄NO₆)₂ was elucidated by single X-ray HR-MS and investigation of catalytic behavior. In particular, masking the Br?nsted acidic COOH catalytic site with dormant COOMe lowered the reaction yield greatly, indicating that two catalytic sites work together to maintain high catalytic efficiency.