1527-99-7Relevant articles and documents
On the solution behaviour of benzyllithium·(-)-sparteine adducts and related lithium organyls - A case study on applying 7Li, 15N{1H} HMQC and further NMR methods, including some investigation into asymmetric synthesis
Casimiro, Maria,Ona-Burgos, Pascual,Meyer, Jens,Styra, Steffen,Kuzu, Istemi,Breher, Frank,Fernandez, Ignacio
, p. 691 - 701 (2013/02/23)
2D 7Li,15N heteronuclear shift correlation through scalar coupling has successfully been applied to several lithium organyls consisting of polydentate N ligands such as N,N,N,N-tetramethylethylenediamine (tmeda), N,N,N,N,N′-pentamethyldiethylentriamine (pmdta) and (-)-sparteine. Structural insights on the conformation of benzyllithium× pmdta (5) in a toluene solution and the strength of ion pairing in combination with PGSE NMR measurements, 1H,1H-NOESY and 1H,7Li-HOESY experiments are presented. By studying in detail the formation of 5 in solution, a transient species has been observed for the first time and assigned to a pre-complex of nBuLi and pmdta. In addition, the solution behaviour of the complex formed between benzyllithium and (-)-sparteine (8) has been studied by PGSE and multinuclear NMR spectroscopy. The straightforward synthesis and first applications in asymmetric lithiations are also reported, which show that the new system benzyllithium×(-)- sparteine (8) provide poorer enantioselective induction than the classical nBuLi×(-)-sparteine (6). The results were supported by deprotonation experiments confirming that the formation of 8 relies on two relevant factors, namely temperature and lithiating reagent. The existence of 8 may thus interfere with the asymmetric induction when the system nBuLi× (-)-sparteine is used in the enantioselective deprotonations of N-Boc-N-(p-methoxyphenyl)- benzylamine conducted in toluene. To pair or not to pair: 2D 7Li,15N heteronuclear shift correlation has been applied to several lithiumorganyls consisting of polydentate N ligands such as N,N,N,N-tetramethylethylenediamine, N,N,N,N,N′- pentamethyldiethylentriamine and (-)-sparteine. In combination with other spectroscopic techniques, details on the formation of the lithiumorganyl- polyamine adducts the strength of ion pairing in solution have been explored (see figure). Copyright
Selective lithiation of 1-bromo-2-((trimethylstannyl)methyl)benzene: Synthesis of 1-bromo-2-(lithiomethyl)benzene, 1-lithio-2-((trimethylstannyl)methyl)benzene, and α,2-dilithiotoluene
De Boer, Henricus J. R.,Akkerman, Otto S.,Bickelhaupt, Friedrich
, p. 2898 - 2903 (2008/10/08)
Reactions of 1-bromo-2-((trimethylstannyl)methyl)benzene (1) with n-butyllithium and tert-butyllithium have been investigated. With n-butyllithium in tetrahydrofuran (THF) at -70°C, the only observed process was lithium-tin exchange, yielding 1-bromo-2-(lithiomethyl)benzene (2). In contrast, lithium-halogen exchange occurred when 1 was treated with tert-butyllithium in diethyl ether at -80°C to give 1-lithio-2-((trimethylstannyl)methyl)benzene (3). α,2-Dilithiotoluene could be prepared in high yield from 3 and tert-butyllithium in either diethyl ether (room temperature) or THF (-80°C).
Nucleophilicity vs. basicity in reactions of n-butyllithium and tert-butyllithium with tetramethylstannane
Farah, Dan,Karol, Thomas J.,Kuivila, Henry G.
, p. 662 - 666 (2008/10/08)
The reactions of n-butyllithium and tert-butyllithium with tetramethylstannane have been examined with the objective of determining the degree of competition between proton abstraction from the methyl groups and nucleophilic displacement of these groups f
