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Conformationally Rigid Chiral Bicyclic Skeleton‐Tethered Bipyridine N,N′‐ Dioxide as Organocatalyst: Asymmetric Ring Opening of meso ‐Epoxides
Author(s) -
Gnanamani Elumalai,
Someshwar Nagamalla,
Sanjeevi Jayakumar,
Ramanathan Chinnasamy Ramaraj
Publication year - 2014
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201400029
Subject(s) - chemistry , desymmetrization , bicyclic molecule , enantioselective synthesis , hypervalent molecule , ring (chemistry) , bipyridine , epoxide , catalysis , stereochemistry , organic chemistry , crystal structure , reagent
The conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N′‐ dioxide (−)‐ 9 has been designed, synthesized and examined as an organocatalyst in the enantioselective ring opening of meso‐ epoxides using tetrachlorosilane (SiCl 4 ). The catalyst (−)‐ 9 is found to exhibit good enantioselectivity for substituted cis ‐stilbene epoxides; whereas, the saturated cyclic meso‐ epoxides display a moderate enantioselectivity. At −30 °C in chloroform, the catalyst (−)‐ 9 with 0.5 mol % loading generated the chlorohydrins in up to 97 % yield with up to 93 % ee . The possible creation of transient axial chiral environment around hypervalent silicon species due to the presence of conformationally rigid chiral bicyclic skeleton tethered bipyridine N,N′‐ dioxide may be responsible for such enantioselectivity observed in the desymmetrization of meso‐ epoxides.