Probing solvent effects on mixed aggregates associating a chiral lithium amide and n-BuLi by NMR: from structure to reactivity.
نویسندگان
چکیده
An NMR study of a 1 : 1 mixture of a chiral lithium amide (4a) and n-BuLi shows that depending on the solvent employed (Et2O or THF) a mixed aggregate can form in proportions that are directly related to the ees measured during the enantioselective alkylation of o-tolualdehyde by these same species.
منابع مشابه
A computational study of the enantioselective addition of n-BuLi to benzaldehyde in the presence of a chiral lithium N,P amide.
In the presence of a chiral lithium N,P amide, alkylation of benzaldehyde results in an enantioselective formation of 1-phenyl-pentanol. This stereoselective addition reaction has herein been studied using dispersion-corrected density functional theory. For five different chiral ligands originating from amino acids the resulting enantioselectivity has been computationally determined and compare...
متن کاملReactivity of individual organolithium aggregates: a RINMR study of n-butyllithium and 2-methoxy-6-(methoxymethyl)phenyllithium.
The high sensitivity of organolithium rates and selectivities to solvation is often attributed to variation in aggregate concentrations. Although lower aggregates appear to be more reactive in most cases, the relative reactivity of aggregates has rarely been determined1a,2,3,4a since kinetic studies are normally performed under CurtinHammett conditions, where contributions to the rate by differ...
متن کاملMixed Aggregates of the Dilithiated Koga Tetraamine: NMR Spectroscopic and Computational Studies.
A combination of (1) H, (6) Li, (13) C, and (15) N NMR spectroscopies and density functional theory computations explores the formation of mixed aggregates by a dilithium salt of a C2 -symmetric chiral tetraamine (Koga's base). Lithium halides, acetylides, alkoxides, and monoalkylamides form isostructural trilithiated mixed aggregates with few exceptions. (6) Li-(13) C and (6) Li-(15) N couplin...
متن کاملSolution structures and reactivities of the mixed aggregates derived from n-butyllithium and vicinal amino alkoxides.
Low-temperature (6)Li, (13)C, and (15)N NMR spectroscopies reveal that mixtures of n-BuLi and (1R,2S)-R'(2)NCH(R)CH(Ph)OLi (ROLi; R = Ph or Me; R'(2)N = pyrrolidino or Me(2)N) in THF/pentane afford a (n-BuLi)(3)(ROLi) (3:1) mixed tetramer and a C(2)-symmetric (n-BuLi)(2)(ROLi)(2) (2:2) mixed tetramer depending on the proportions of the reactants. The corresponding (n-BuLi)(ROLi)(3) (1:3) mixed ...
متن کاملNMR studies of chiral lithium amides with phosphine chelating groups reveal strong Li-P-interactions in ethereal solvents
Chiral lithium amides with a chelating diphenylphosphine group have previously been found to mediate excellent enantioselectivity in the asymmetric addition of alkyllithiums to benzaldehyde. NMR studies reveal for the first time that chiral lithium amides can form chelating dimeric complexes with P-Li interactions in both diethyl ether and THF. The two lithium atoms in the dimer are found to be...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Dalton transactions
دوره 43 38 شماره
صفحات -
تاریخ انتشار 2014