Lithium Alkoxide Research Articles

A rapid-injection NMR study of the effect of lithium alkoxides on the butyllithium-initiated polymerization and propagation of styrene

In studies carried out in THF at −80°C, lithium n-butoxide was found to speed up the initiation and to an even greater extent the rate of propagation in the alkyllithium-initiated polymerization of styrene. Bulky alkoxides were found to slow down the rate of polymerization by slowing both initiation and propagation although initiation was decreased to a greater extent than propagation. Five equivalents of lithium tert-butoxide stopped the initiation completely under these reaction conditions when n-butyllithium was used as an initiator. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1157–1168, 1999

The formation of phase pure lithium aluminate from the bulky lithium and aluminum alkoxides

Lithium aluminate, LiAlO2, is a potential candidate for tritium breeder of fusion reactor or electrolyte matrix of molten carbonate fuel cell due to its chemical and thermal stability as well as low radiation damage susceptibility [1, 2]. Three allotropic forms of LiAlO2 are known: α-, β-, and γ -LiAlO2, which have hexagonal, monoclinic, and tetragonal structures, respectively. The most stable polymorph is γ -LiAlO2. The αor β-LiAlO2 phase transforms to γ -LiAlO2 at elevated temperature. There are several methods to prepare lithium aluminate powders [1–3]. Generally, the sol-gel method has advantages over solid state reaction methods in intimate mixing of reactants, high purity, and low processing temperature [4, 5]. Kwon and Park prepared lithium aluminate powders by the sol-gel method and studied the effect of precursors on the preparation of lithium aluminate [3]. They found that the properties of the product powders were highly dependent on the length of alkoxides that were used as starting materials of the sol-gel method. Phase pure gamma lithium aluminate was prepared and processing temperature was lowered when the alkoxides with long alkoxy groups were used as starting materials. In this letter, we tried to elucidate the reason why the starting materials with long alkoxy groups resulted in the better phase purity when gamma lithium aluminate powders were prepared from lithium and aluminum alkoxides via the sol-gel method. Two types of gel powders were prepared by the sol-gel method from two precursor systems; lithium ethoxide-aluminum ethoxide and lithium butoxidealuminum butoxide system. The preparation procedures were described in the paper of Kwon and Park [3]. Most of the reagents used in this study were products of Aldrich Chemical Company. All reagents were used without further purification except alcohols from which moisture was removed by molecular sieve 3A. Differential thermal analysis (TG-DTA, TA Instrument, SDT2960), and infrared spectrometry (IR, Perkin Elmer, 1725X) were used to compare the two types of gel powders. For the thermal analysis, 20–30 mg of the powders were heated in air flow of 100 ml/min. For the IR analysis, gel powders were dried under reduced pressure and embedded in optical grade potassium bromide (KBr) pellets. To examine the difference of gel powders prepared from the two different alkoxides, the rate of lithium aluminate formation was measured by Kissinger method [6]. In this method, apparent activation energy is measured from the shift of the peak temperature:

Hexameric chiral α-amino lithium alkoxides: a solid-state and theoretical structural investigation

The nucleophilic reagents lithium N-methylpiperazide, 1-Li, and lithium N,N,N′-trimethylethylenediamide, 2-Li, react with 1 equiv. of 4-methoxybenzaldehyde and 2-methylbenzaldehyde respectively to afford the corresponding chiral α-amino lithium alkoxides, (3)6·2PhMe·THF and (4)6·2PhMe, which are hexamers in the solid state. Stabilisation of the metal centres is assisted by dative coordination of the dialkylamine α-N-centres. While for (3)6·2PhMe·THF this is rationalised in terms of steric constraints imposed by the employment of a heterocyclic dialkylamine, for (4)6·2PhMe it contrasts starkly with previously observed structural analogues. Abinitio MO calculations are employed to investigate the relationship between structure and ligand chirality.

Dynamic processes in organolithium chemistry: tetrameric and ‘open’ tetrameric chiral α-amino lithium alkoxides

Lithium N,N,N′-trimethylethylenediamide, LiN(Me)(CH2)2NMe2, 1-Li, reacts with 1 equiv. of benzaldehyde to afford the corresponding chiral α-amino lithium alkoxide 2, which in the solid state is a conventional pseudo-cubane tetramer. Reaction of 1-Li with o-methoxybenzaldehyde affords instead a novel ‘open’ pseudo-cubane tetramer 3, wherein the coordinative mode of the potentially bidentate N,N,N′-trimethylethylenediamino moiety can be related to ligand chirality. Employment of p-methoxybenzaldehyde results in the isolation of a tetramer 4, whose solid-state structure is intermediate between those of 2 and 3 and therefore suggests that fluxional processes may operate. Extensive studies of 2–4 in non-donor solution indicate diverse and complex behaviour.

New 1-amino-1,2-diphenylethanols as ligands for the enantioselective addition of alkyllithiums to benzaldehyde

In the presence of equimolar amounts of lithium alkoxides derived from N-substituted 2-amino-1,2-diphenyl-ethanols, alkyllithium reagents add to benzaldehyde to furnish optically active secondary alcohols with enantiomeric excesses of up to 86%. The best results were obtained using the N-isopropyl- N-methyl substituted amino-alcohol.

Practical Asymmetric Synthesis of Efavirenz (DMP 266), an HIV-1 Reverse Transcriptase Inhibitor

A highly enantioselective and practical synthesis of the HIV-1 reverse transcriptase inhibitor efavirenz (1) is described. The synthesis proceeds in 62% overall yield in seven steps from 4-chloroaniline (6) to give efavirenz (1) in excellent chemical and optical purity. A novel, enantioselective addition of Li-cyclopropyl acetylide (4a) to p-methoxybenzyl-protected ketoaniline 3a mediated by (1R,2S)-N-pyrrolidinylnorephedrine lithium alkoxide (5a) establishes the stereogenic center in the target with a remarkable level of stereocontrol.

An Advanced Tool for the Selection of Electrolyte Components for Rechargeable Lithium Batteries

The solid electrolyte interphase (SEI) plays a key role in lithium‐metal, lithium‐alloy, and lithium‐ion batteries. The SEI on both lithium and carbonaceous electrodes consists of many different materials including LiF, , lithium alkoxides, nonconductive polymers, and more. Close to the lithium or the SEI consists of the thermodynamically stable anions, such as , and halides. Close to the solution the SEI also contains partially reduced materials such as polyolefins, semicarbonates, etc. These materials form simultaneously and precipitate on the electrode as a mosaic of microphases. These phases may, under certain conditions, form separate layers, but in general it is more appropriate to treat them as heteropolymicrophases. The SEI composition and properties depend strongly on electrolyte composition and on other factors. Rapid formation of the SEI is important in all lithium batteries, especially in the case of lithium‐ion cells with graphite anodes. Hence SEI precursors must be selected from a group of materials that have high exchange current density (i0) for reduction. As it is difficult to measure i0 on solid electrodes and only limited data, if any, are available, it is suggested to use the data bank for the rate constant for the reduction of electrolyte components by hydrated electrons . We have demonstrated that the rate constants of the reactions of solvated electrons and electrolyte components and impurities correlate well with the formation voltage of SEI and with SEI composition. Thus, the rate constants (ke) for these reactions are proposed as a tool for the first screening of electrolyte components when a new electrolyte is designed.

Study of the reactions of Li with tetrahydrofuran and propylene carbonate by photoemission spectroscopy

The reaction of Li with two organic solvents of technical importance in Li batteries, tetrahydrofuran (THF) and propylene carbonate (PC), were studied in ultrahigh vacuum by photoemission spectroscopy. The organic condensate layers were formed by dosing thin (6–10 nm) films of Li at 120–135 K, with the reactions monitored by x-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy upon subsequent warming of the sample. Activation of the first layer of THF by Li starts at a temperature as low as 120 K. Polymerization of tetrahydrofuran (THF) (forming poly-THF) occurs upon melting near 180 K, but is accompanied by chain-terminating reactions that form lithium alkoxide(s) and hydrocarbon gas(es), such as ethylene and/or propylene. Between 180 and 320 K, there is progressively greater conversion of poly-THF to alkoxide such that at 320 K, the surface film is almost entirely composed of alkoxide. At or near its bulk melting temperature of 220 K, essentially all of the PC remaining on the surface has reacted with Li to form an alkyl carbonate. With increasing temperature, part (25%–33%) of the alkyl carbonate decomposes to form an alkoxide. The alkyl group in the organo–Li compounds derived from PC are most probably propylene. There is no evidence of the formation of any gaseous products containing carbon or oxygen at temperatures below 320 K under the conditions of these experiments. Of particular relevance to battery technology, however, is that in both cases the organo–Li layers that have formed at 270–320 K were formed in the presence of excess unreacted Li, which is the usual circumstance in a real battery, and that no evidence was found of inorganic Li carbonate as a product of the reaction with PC.

Solvent-induced stereospecific isomerization of an allylic alcohol to a homoallylic alcohol catalyzed by a chiral lithium amide

Deprotonation of cyclohexene oxide, 1, by lithium (S)-2-(1-pyrrolidinylmethyl)pyrrolidide, 2-Li, on changing the solvent from tetrahydrofuran (THF) to, for example, 2,5-dimethyltetrahydrofuran (DMTHF) or diethyl ether (DEE) has been shown to yield, besides the lithium alkoxide of 2-cyclohexene-1-ol, 3-Li, the lithium alkoxide of the homoallylic alcohol 3-cyclohexene-1-ol, 4-Li. It was shown that compound 4-Li is formed from 3-Li. No such rearrangement has been observed in THF. We have now shown that the solvent-induced isomerization of the lithium alkoxide of (S)-3-methyl-2-cyclohexene-1-ol, (S)-5-Li, catalyzed by 2-Li to the lithium alkoxide of (S)-3-methyl-3-cyclohexene-1-ol, (S)-6-Li, is 100% stereospecific. Furthermore, deuterium-labeling experiments suggest that the rearrangement of the proton is close to 100% intramolecular.Key words: 1,3-proton transfer, chiral lithium amide, intramolecular, solvent-induced isomerization, stereospecific.

Lithium Ephedrate-Mediated Addition of a Lithium Acetylide to a Ketone: Solution Structures and Relative Reactivities of Mixed Aggregates Underlying the High Enantioselectivities

Addition of lithium cyclopropylacetylide (RLi) to ArCOCF3 mediated by 1(R),2(S)-R2NCH(CH3)CH(Ph)OLi (ROLi; R2N = pyrrolidino) occurs with 50:1 enantioselectivity (Thompson, A. S. et al. Tetrahedron. Lett. 1995, 36, 8937). Low-temperature 6Li and 13C NMR spectroscopies reveal lithium cyclopropylacetylide in THF to be a dimer−tetramer mixture and the lithium alkoxide to be a complex mixture of oligomers. Mixtures of RLi and ROLi in THF afford stoichiometry-dependent mixtures of 3:1, 2:2, and 1:3 mixed tetramers. The dramatic improvements in the stereochemistry of 1,2-additions caused by aging the reaction at ambient temperatures are shown to coincide with unusually slow aggregate equilibrations. ReactIR studies showed that the previously detected requirement for 2 equiv of lithium acetylide per ketone stems from autoinhibition rather than from a proton abstraction of an NH moiety in the substrate. Semiempirical (MNDO) computational studies support a stereochemical model based upon 1,2-addition via a C2 symm...

Synthesis of New Phosphino Amino Alcohol Ligands via Ortho-Alkyllithiation Reactions. Versatile Coordination Behavior toward Copper(I) and Palladium(II)

2-[Methyl(2-methylphenyl)amino]ethanol undergoes an ortho-alkyllithiation reaction with n-butyllithium to lead to a new mixed benzyllithium−lithium alkoxide. This organolithium species reacts with PPh2Cl, with selective P−C bond formation, to afford the ligand 2-[methyl(2-((diphenylphosphino)methyl)phenyl)amino]ethanol L1. The coordination of the ligand L1 to copper(I) leads to the complex [Cu(L1)2](BF4), whose structure has been determined by an X-ray diffraction study. In the solid state, one of the ligands acts as a monodentate phosphine while the other adopts a tridentate P,N,O coordination mode. A variable-temperature 31P NMR study demonstrated the existence of an equilibrium between the two modes in solution, with a coalescence temperature of ca. 0 °C, indicating a double-hemilabile behavior for the nitrogen and the oxygen functions. L1 reacts with [Pd(Me)(Cl)(COD)] to give a dinuclear complex in which the ligand appears to behave as a bridging anionic P,O ligand. Such a complex could serve as a model for a key intermediate in the proposed mechanism for the homogeneous catalysis of the methoxycarbonylation of propyne by certain palladium(II) complexes containing P,N ligands. L1 can undergo a second ortho-alkylmetalation reaction with n-butyllithium which, after addition of PPh2Cl, provides the new ligand 2-{methyl[2-(bis(diphenylphosphino)methyl)phenyl]amino}ethanol (L2) in high yield.

The synthesis and solid-state and solution structures of an unprecedented mixed chiral α-amino lithium alkoxide–lithium alkoxide aggregate

Lithium N,N,N′-trimethylethylenediamide, LiN(Me)(CH2)2NMe2, reacts with 1 equiv. of 2-trifluoromethylbenzaldehyde, 2-F3CC6H4CHO, to afford a surprising tetranuclear mixed aggregate containing three chiral α-amino lithium alkoxide molecules which associate in a highly unusual fashion, the fourth molecule, the benzyl alkoxide reduction product, forming by an inter-molecular LiH transfer.

Solvent-induced stereospecific isomerization of an allylic alcohol to a homoallylic alcohol catalyzed by a chiral lithium amide

Deprotonation of cyclohexene oxide, 1, by lithium (S)-2-(1-pyrrolidinylmethyl)pyrrolidide, 2-Li, on changing the solvent from tetrahydrofuran (THF) to, for example, 2,5-dimethyltetrahydrofuran (DMTHF) or diethyl ether (DEE) has been shown to yield, besides the lithium alkoxide of 2-cyclohexene-1-ol, 3-Li, the lithium alkoxide of the homoallylic alcohol 3-cyclohexene-1-ol, 4-Li. It was shown that compound 4-Li is formed from 3-Li. No such rearrangement has been observed in THF. We have now shown that the solvent-induced isomerization of the lithium alkoxide of (S)-3-methyl-2-cyclohexene-1-ol, (S)-5-Li, catalyzed by 2-Li to the lithium alkoxide of (S)-3-methyl-3-cyclohexene-1-ol, (S)-6-Li, is 100% stereospecific. Furthermore, deuterium-labeling experiments suggest that the rearrangement of the proton is close to 100% intramolecular.Key words: 1,3-proton transfer, chiral lithium amide, intramolecular, solvent-induced isomerization, stereospecific.

Asymmetric Induction in Intramolecular SN2' Reaction. Enantioselective Synthesis of Cyclopenta[b]benzofuran with Chiral Lithium Alkoxides

Asymmetric Induction in Intramolecular S_N2' Reaction. Enantioselective Synthesis of Cyclopenta[<i>b</i>]benzofuran with Chiral Lithium Alkoxides

Low temperature synthesis and electrochemical characteristics of LiFeO 2 cathodes

Two rechargeable polymorphs of LiFeO 2 have been synthesized at low temperatures of less than 250 °C via a novel H +/Li + ionic-exchange reaction in an alcoholic solution using stoichiometric amounts of lithium alkoxide and iron oxyhydroxide as the starting materials. The reaction, which proceeded in a topotactic manner, resulted in new polymorphs in the LiFeO 2 family with similar crystal structures to the parent materials. Two types of LiFeO 2, the corrugated layer and goethite type, were rechargeable in lithium cells with a cycling capacity of 0.2–0.4 Li/LiFeO 2 in the 1.5–4.5 V range, unlike the other six non-rechargeable polymorphs reported so far. A preliminary X-ray diffraction study on structural changes in the cathode during cycling showed a minimal lattice parameter change for corrugated layer LiFeO 2 and a noticeable a-lattice shrinkage/expansion of about 1% for goethite-type LiFeO 2.

Ligand effects in selective addition reactions of organoindium reagents with carbonyl compounds

The reaction of the allyl indium sesquibromide (CH 2=CHCH 2) 3In 2Br 3 with four equivalents of a bulky lithium alkoxide ((CH 3) 3COLi or (CH 3) 3CCH 2OLi) results in modified reagents which show unusual degrees of chemo- and stereoselectivity in reactions with carbonyl compounds. For example, in reactions with cyclohexanone derivatives, 84–93% equatorial attack with preferential formation of the axial alcohols is observed. Chiral aldehydes react in a highly diastereoselective manner.

Chemical Reaction of Lithium Surface during Immersion in LiClO4 or LiPF6 / DEC Electrolyte

Chemical reactions of lithium with diethyl carbonate (DEC) containing or ( or ) were studied by using in situ Fourier transform infrared (FTIR) and x‐ray photoelectron spectroscopies. The in situ FTIR spectra for both electrolytes show a penetration of the DEC electrolyte into the native surface film on lithium foils at the initial period of immersion. In the case of , the DEC solvent contacts the lithium metal, and then reacts directly with lithium metal to form reductive decomposition products of DEC, such as lithium alkylcarbonate, lithium alkoxide, and . When was used as the electrolyte, the native surface film was gradually etched and then changed to a bilayer surface film. The in situ FTIR spectra showed no formation of decomposition products of DEC. This means that the surface film consisting of was highly effective in suppressing the direct chemical reactions of DEC with lithium metal.

Use of Manganese(II)−Schiff Base Complexes for Carrying Polar Organometallics and Inorganic Ion Pairs

This report concerns the carrier properties of [Mn(acacen)]-derived compounds toward polar organometallics, inorganic ion pairs, and salts. Such properties are the consequence of Mn(II) behaving as a Lewis acid and the O&arcraise;O bite of the bidentate Schiff base ligand toward alkali cations. The starting compounds, which occur in a dimeric form, [Mn(acac-L-en)](2) [L' = CH(2)CH(2) (1); L" = C(6)H(10) (2); L"' = R,R-C(6)H(10) (3)] have been synthesized either via a metathesis reaction from MnCl(2) or using [Mn(3)Mes(6)]. The reaction of 1-3 with lithium organometallics allowed the isolation of [Mn(acac-L-en)(R)Li(DME)] [R = Me, L = L' (4); R = Ph, L = L' (5); R = Mes, L = L' (6); R = Me, L = L" (7); R = Me, L = L"' (8)] as metalated forms, where the alkyl or aryl group is sigma-bonded to Mn(II), while the lithium cation is anchored to the Schiff base ligand. The metalated forms 4-8 react with PhCHO to give the corresponding lithium alkoxide, which remains bound in its ion-pair form to the [Mn(acacen)] skeleton in [Mn(2)(acac-L'-en)(2)Li(2)(OCH(Ph)Me)(2)](n)() (9). The use of 8, which has a chiral bridge across two nitrogen atoms, did not lead to a significant asymmetric induction in the reaction with PhCHO, because of the long separation between the lithium cation and the stereogenic center. The metalated form 4 was able to transfer the methyl group to the nitrile function to give the corresponding lithium-imide which then remains bonded to [Mn(acacen)] as the ion pair in a dimeric structure, as revealed for [Mn(2)(acac-L'-en)(2)Li(2)(DME){N=C(Ph)Me}(2)](n)() (10). Their reaction with 1 appears to depend on the steric bulkiness of the alkyl group in NaOR, resulting in either monomeric adducts, i.e. in [Mn(acac-L'-en)(2,6-Bu(t)(2)C(6)H(3)O)Na(DME)(2)] (11.2DME), or polymeric structures, like in [Mn(acac-L'-en)Na(DME)(&mgr;-OEt)](n)() (13). All the dimeric units reported in this paper show a slight antiferromagnetic coupling between the two Mn(II) assisted by bridging alkoxo groups.

Diphenyl methylphosphonate as a phosphonylation reagent with high diastereoselectivity at phosphorus

Reaction of diphenyl methylphosphonate with lithium alkoxides generated in situ from alcohols and butyllithium gives phenyl alkyl methylphosphonate diesters even with hindered alcohols and with high diastereoselectivity at phosphorus.

Convergent synthetic routes to heterobimetallic compounds: Crystal and molecular structure of 1-( η5-cyclopentadienyl manganese tricarbonyl)-1-( η6-phenyl chromium tricarbonyl) ethanol

13 heterobimetallic compounds have been prepared by a convergent synthetic strategy employing reactions of a lithiocyclopentadienyl or lithioarene metal complex with formyl, acetyl or carbomethoxy functionalized derivatives of a second metal. The resulting lithium alkoxide products were converted to the corresponding alcohols by dilute acid work-up. Two methanol derivatives were successfully converted to their corresponding methane derivatives by reaction with trifluoroacetic acid followed by reaction of the resultant carbocation with sodium tetrahydroborate. Reaction of 1-[ η 6-C 6H 5Cr(CO) 3]-1-[ η 5-C 5H 4Mn(CO) 3]C 2H 3OH with trifluoroacetic acid results in dehydration to yield the corresponding ethene derivative. The molecular structure of 1-[ η 6-C 6H 5Cr(CO) 3]-1-[ η 5-C 5H 4Mn(CO) 3]C 2H 3OH was determined. monoclinic, P2 1/ c, a = 7.936(2), b = 19.844(8), c = 11.774(4) A ̊ , β = 91.58(2)°, V = 1853(1) A ̊ 3, Z = 4, R(F) = 4.52% .