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Keywords:

  • amino alcohols;
  • asymmetric catalysis;
  • enantioselectivity;
  • ring opening;
  • titanium

Abstract

New chiral ligands, (S,R,S)-1, (S,S,S)-1, (S,S,R)-1, (S,R,R)-1, (R,R,R)-1, (R,R,S)-1, (R,S,S)-1, (R,S,R)-1, (S,R,S)-2, (S,S)-3 and (R,S)-4 with diverse stereogenic centers arising from various diastereomeric combinations of aminoalcohol functionality with (R)- and (S)-1,1-binaphthol, were prepared and characterized. Catalytically active Ti complexes were generated in situ in the presence of water for the enantioselective ring-opening reaction of meso-stilbene oxide, cyclohexene oxide, cyclopentene oxide, and cis-butene oxide with different anilines as nucleophile. Significantly, catalysts Ti-(S,R,S)-1 and Ti-(R,S,S)-1 (15 mol %) produced syn-beta-amino alcohols of meso-stilbene oxide with (1S,2S) and (1R,2R) configuration respectively in excellent yields (>98 %) and enantioselectivities (ee value >99 %) in 10 h at room temperature. However, aliphatic/cyclic epoxides with aniline gave better performance with the catalyst Ti-(S,R,R)-1. The complex Ti-(S,R,S)-1 was successfully subjected to catalyst recovery and recyclability experiments over 6 cycles in the asymmetric ring-opening of meso-stilbene oxide with aniline with retention of performance.