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Synthesis of Chiral Ligands with Multiple Stereogenic Centers and Their Application in Titanium(IV)‐Catalyzed Enantioselective Desymmetrization of meso‐ Epoxides
Author(s) -
Kumar Manish,
Kureshy Rukhsana I.,
Ghosh Debashis,
Khan Noorul H.,
Abdi Sayed H. R.,
Bajaj Hari C.
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201200912
Subject(s) - enantioselective synthesis , stereocenter , desymmetrization , chemistry , catalysis , cyclohexene oxide , cyclopentene , nucleophile , aniline , oxide , medicinal chemistry , diastereomer , ring (chemistry) , stereochemistry , cyclohexene , organic chemistry
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 (1 S, 2 S ) and (1 R, 2 R ) 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.