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Kinetic and NMR Spectroscopic Studies of Chiral Mixed Sodium/Lithium Amides Used for the Deprotonation of Cyclohexene Oxide
Author(s) -
Sott Richard,
Granander Johan,
Williamson Carl,
Hilmersson Göran
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500121
Subject(s) - chemistry , tetrahydrofuran , lithium amide , lithium (medication) , deprotonation , ether , diethyl ether , amide , alkali metal , sodium , medicinal chemistry , cyclohexene oxide , butyllithium , inorganic chemistry , organic chemistry , solvent , cyclohexene , enantioselective synthesis , catalysis , medicine , ion , endocrinology
The mixed‐metal complex formed from n ‐butylsodium, n ‐butyllithium, and a chiral amino ether has been studied by NMR spectroscopy. Three different mixed‐metal amides were used as chiral bases for the deprotonation of cyclohexene oxide. The selectivity and initial rate of reaction were compared for sodium–amido ethers, lithium–amido ethers, and mixtures of sodium and lithiumamido ethers in diethyl ether and tetrahydrofuran, respectively. The mixed sodium/lithium amides are more reactive than the single sodium and lithium amides, whereas the stereoselectivities are higher when lithium amides are used. The alkali‐metal/γ‐amido ethers exhibit both higher initial reaction rates and stereoselectivities than their β‐amido ether analogues. NMR spectroscopic studies of mixtures of n ‐butylsodium ( n BuNa), n ‐butyllithium ( n BuLi), and the γ‐amino ethers in diethyl ether show the exclusive formation of dimeric mixed‐metal amides. In diethyl ether, the lithium atom of the mixed‐metal amide is internally coordinated and the sodium atom is exposed to solvent; however, in tetrahydrofuran, both metals are internally coordinated.