Titanium complexes based on chiral enantiopure dialkanolamines: synthesis, structures and catalytic activity

摘要

New chiral enantiopure tridentate ligands (dialkanolamines) RN(CHR~3CR~1R~2OH)(CHR~4CR~5R~6OH) 10-17 were synthesized by the opening of the epoxide ring by the action of the amines or alkanolamines. Titanium complexes, viz. [RN(CHR~3CR~1R~2O)(CHR~4CR~5R~6O)]Ti(O-i-Pr)2 18-23 and [RN(CHR~3CR~1R~2O)(CHR~4CR~5R~6O)]2Ti 25-31 were synthesized by treatment of Ti(O-i-Pr)4 with one or two equivalents of corresponding dialkanolamines. Complex (R)-PhCH(Me)N(CH2C(Me)2O)2TiCl2~*HNMe2 24 was obtained from the reaction of one equivalent of dialkanolamine 10 with (Me2N)2TiCl2. The composition and structure of all novel compounds were established by ~1H and ~(13)C NMR spectroscopy as well as elemental analysis. The possible solution structures of 18-31 are discussed. The single-crystal X-ray diffraction study of 23, 25-28, 30, 31 indicates monomeric structures in the solid state. Chiral complexes 20, 22, 23, 25, 26, 30 were tested as chiral catalysts in the Abramov reaction and demonstrated moderate enantiomeric activity.