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).
Reactions of organotin hydrides with lithium diisopropylamide and organolithiums. Reactivities of the intermediates and of the lithium hydride produced
Reimann, Werner,Kuivila, Henry G.,Farah, Dan,Apoussidis, Theodorus
, p. 557 - 565 (2008/10/08)
Equimolar lithium diisopropylamide (LDA) and trimethyltin hydride (TMTH) react in tetrahydrofuran (THF) to form diisopropylamine and (trimethylstannyl)lithium, but in diethyl ether or hexanes 2 mol of TMTH is required for complete reaction and the products are diisopropylamine, hexamethylditin, and lithium hydride. When organic halides are present in this reacting system, reduction to alkane or substitution to form the trimethylalkyltin may occur depending on the nature of the halide. These and other observations suggest that (trimethylstannyl)lithium is formed as an intermediate yielding the tetraalkyltin. Studies on the products and stoichiometries of the reductions of alkyl bromides in ether and hexanes suggest that three reducing agents may be involved: TMTH, [Me3Sn(H)N-i-Pr2]-, and [Me3SnSn(H)Me3]-. The latter predominates in ether, and either or both of the others predominate in hexanes. Formation of methylcyclopentane from 1-bromo-5-hexene suggests involvement of a free radical mechanism. When methyllithium is used instead of LDA in the reaction with TMTH, the products are tetramethyltin and lithium hydride. This reaction can also be diverted to reduction by the presence of primary bromides. Aryl bromides react in both systems, but the yields of either substitution or reduction products are low. The lithium hydride formed in these reactions is extremely reactive as a base as shown by a brief study of its reaction with weak carbon acids and amines and as a nucleophile by its reaction with hexamethylditin to form (trimethylstannyl)lithium in THF.
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
REGIOSPECIFIC SYNTHESIS OF AROMATIC COMPOUNDS VIA ORGANOMETALLIC INTERMEDIATES. II. 1,3,5-(TRIMETHYLMETAL(IV))BENZENE COMPOUNDS
Chen, Grace J.,Tamborski, Christ
, p. 149 - 158 (2007/10/02)
Sequential metal-halogen exchange reactions between n-C4H9Li and 1,3,5-tribromobenzene and reaction at each step with (CH3)3MIVCl(MIV = Si, Ge, Sn) has provided a 1,3,5-(trimethylmetal(IV))benzene compound.This class of compounds can be synthesized either trough a step-wise procedure, where the various intermediates are isolated, or in a continuous metal-halogen exchange process without isolation of various intermediates.
REACTIONS OF TRIMETHYLTINSODIUM WITH ALKYL HALIDES. EFFECTS OF STRUCTURE AND SOLVENT ON COURSE OF REACTION AND REACTIVITY
Kuivila, Henry G.,Reeves, William G.
, p. 801 - 808 (2007/10/02)
The reactions of eleven alkyl chlorides and bromides with trimethyltinsodium have been examined.It has been found that primary and secondary halides react smoothly and rapidly to provide good yields of substitution products in THF and TG at Oo.The reaction is less satisfactory for allyl bromide and unsatisfactory for cinnamyl chloride and tertiary halides.Trimethyltinsodium and 2-chlorobutane react with second order kinetics.Relative reactivities of the halides have been determined in the two solvents and are discussed.Lithium, sodium and potassium as counterions yielded the same results in the reaction of the trimethyltinalkils with primary, secondary and tertiary butyl bromides in THF.
