One water molecule stabilizes the cationized arginine zwitterion

Singly hydrated clusters of lithiated arginine, sodiated arginine, and lithiated arginine methyl ester are investigated using infrared action spectroscopy and computational chemistry. Whereas unsolvated lithiated arginine is nonzwitterionic, these results provide compelling evidence that attachment of a single water molecule to this ion makes the zwitterionic form of arginine, in which the side chain is protonated, more stable. The experimental spectra of lithiated and sodiated arginine with one water molecule are very similar and contain spectral signatures for protonated side chains, whereas those of lithiated arginine and singly hydrated lithiated arginine methyl ester are different and contain spectral signatures for neutral side chains. Calculations at the B3LYP/6-31++G** level of theory indicate that solvating lithiated arginine with a single water molecule preferentially stabilizes the zwitterionic forms of this ion by 25-32 kJ/mol and two essentially isoenergetic zwitterionic structure are most stable. In these structures, the metal ion either coordinates with the N-terminal amino group and an oxygen atom of the carboxylate group (NO coordinated) or with both oxygen atoms of the carboxylate group (OO coordinated). In contrast, the OO-coordinated zwitterionic structure of sodiated arginine, both with and without a water molecule, is clearly lowest in energy for both ions. Hydration of the metal ion in these clusters weakens the interactions between the metal ion and the amino acid, whereas hydrogen-bond strengths are largely unaffected. Thus, hydration preferentially stabilizes the zwitterionic structures, all of which contain strong hydrogen bonds. Metal ion size strongly affects the relative propensity for these ions to form NO or OO coordinated structures and results in different zwitterionic structures for lithiated and sodiated arginine clusters containing one water molecule.     

Direct transformation of silyl enol ethers into functionalized allenes

The first elimination reactions of silyl enol ethers to lithiated allenes are reported. These reactions allow a direct transformation of readily available silyl enol ethers into functionalized allenes. The action of three to four equivalents of lithium diisopropylamide (LDA) on silyl enol ethers results in the formation of lithiated allenes by initial allylic lithiation, subsequent elimination of a lithium silanolate, and finally, lithiation of the allene thus formed. Starting with amide-derived silyl imino ethers, lithiated ketenimines are obtained. A variety of reactions of the lithiated allenes with electrophiles (chlorosilanes, trimethylchlorostannane, dimethyl sulfate and ethanol) were carried out. Elimination of silanolate is observed only for substrates that contain the hindered SiMe2tBu or Si(iPr)3 moiety, but not for the SiMe3 group. The reaction of 1,1-dilithio-3,3-diphenylallene with ketones provides a convenient access to novel 1,1-di(hydroxymethyl)allenes which undergo a domino Nazarov-Friedel-Crafts reaction upon treatment with p-toluenesulfonic acid.     

Scope and limitations of the catalytic asymmetric rearrangement of epoxides to allylic alcohols using chiral lithium amide bases/lithiated imidazoles

The catalytic asymmetric rearrangement of functionalised cyclohexene and cyclopentene oxides has been studied using sub-stoichiometric amounts of a chiral lithium amide in combination with a stoichiometric amount of three different lithiated imidazoles. 1-Methylimidazole that had been lithiated at the C-2 aryl position gave the highest enantioselectivity (82% ee). With 1,2-dimethylimidazole that had been lithiated at the C-2 methyl group, epoxide ring opening occurred as an unexpected and competing process. Ultimately, ring opening was suppressed using a more sterically hindered imidazole. In all catalytic examples, a racemic background reaction (presumably due to rearrangement by the lithiated imidazoles) was observed.     

Lithiated Primary Amine—A New Material for Hydrogen Storage

A facile method for synthesizing crystalline lithiated amines by ball milling primary amines with LiH was developed. The lithiated amines exhibit an unprecedented endothermic dehydrogenation feature in the temperature range of 150–250 °C, which shows potential as a new type of hydrogen storage material. Structural analysis and mechanistic studies on lithiated ethylenediamine (Li₂EDA) indicates that Li may mediate the dehydrogenation through an α,β‐LiH elimination mechanism, creating a more energy favorable pathway for the selective H₂ release.     

Characterization of iridoids by fast atom bombardment mass spectrometry followed by collision-induced dissociation of

Fast atom bombardment mass spectra of a series of naturally occurring and synthetically modified iridoid glycosides were studied using lithium cationization and collision-induced dissociation of the resulting [M+Li]+ ions. Lithium cationization leads to the unambiguous determination of the molecular masses of these compounds. Collision-induced dissociation of the lithiated molecular ions give valuable structural information regarding the nature of the substituent on both the aglycone and the sugar moieties. The characteristic fragmentation pathways identified are (1) elimination of neutral molecules comprising the substituents on either the aglycone or sugar moieties, (2) formation of lithiated aglycone and their fragment ions, (3) formation of lithiated sugar and their fragment ions, (4) fragmentation corresponding to the cleavage of the aglycone or sugar ring and (5) fragmentation characteristic of the substituents present in either the aglycone or sugar parts of the molecule. Elimination of two acyloxy radicals from the lithiated molecular ion is a characteristic fragmentation in the case of acyloxy derivatives.     

Structures and hydration enthalpies of cationized glutamine and structural analogues in the gas phase

The structures of lithiated and sodiated glutamine, both with and without a water molecule, are investigated using experiment and theory. Loss of water from these complexes and from lithiated and sodiated complexes of asparagine methyl ester, asparagine ethyl ester, and glutamine methyl ester is probed with blackbody infrared radiative dissociation experiments performed over a wide temperature range. Threshold dissociation energies, E(o), for loss of a water molecule from these complexes are obtained from master equation modeling of these data. The values of E(o) are 63 +/- 1 and 53 +/- 1 kJ/mol for the lithiated and sodiated glutamine complexes, respectively. These values are similar to those for the nonzwitterionic model complexes and are in excellent agreement with calculated values. In contrast, water binding to the zwitterionic form is calculated to be significantly higher. These results indicate that glutamine in these lithiated and sodiated complexes with a water molecule are nonzwitterionic. Complexes with the asparagine side chain have slightly higher E(o) values than those with the glutamine side chain, a result consistent with more effective solvation of the metal ion due to the slightly longer side chain of glutamine. Calculations indicate that lithiated and sodiated glutamine are nonzwitterionic, with the metal ion interacting with the amine nitrogen and carbonyl oxygen from the amino acid backbone and the amide oxygen of the side chain. Addition of a water molecule does not affect the lowest-energy structure of lithiated glutamine, whereas, for sodiated glutamine, the lowest-energy zwitterionic and nonzwitterionic structures are essentially isoenergetic.     

New stabilising groups for lateral lithiation of ortho-cresol derivatives

1-(2-Methoxyethoxy)-2-methylbenzene and 1-(2-dimethylaminoethoxy)-2-methylbenzene have been lithiated using sec-BuLi under a variety of conditions and the laterally lithiated species trapped with electrophiles.     

The lithiation of gem-bis (pyrazol-1-yl)alkanes

The title compounds can be lithiated at the inter-ring carbon atom to give carbanions which react with a variety of electrophiles. Lithiation can also be directed to the 5-position of the ring.     

Preparation of Benz[b]Indeno[1,2-e]Pyran-11(6H)-Ones and Benz[b]Indeno[1,2-e]Thiopyran-11(6H)-One from Dilithiated 2-Indanone and Lithiated Methyl Salicylates or Lithiated Methyl Thiosalicylate

Dilithiated 2-indanone was prepared with excess lithium diisopropylamide, and the resulting intermediate was condensed with several lithiated methyl salicylates or lithiated methyl thiosalicylate, which was followed by acid cyclization to benz[b]indeno[1,2-e]pyran-11(6H)-ones 3--9 or benz[b]indeno[1,2-e]thiopyran-11(6H)-one 10, which are rare fused-ring indeno-chromones and a new indeno-thiochromone, respectively.     

New stabilising groups for lateral lithiation of ortho-cresol derivatives and a new route to 2-substituted chromans

2-(2-Methoxyethoxy)-toluene and 2-(2-dimethylaminoethoxy)-toluene have been lithiated using sec-BuLi under a variety of conditions and the laterally lithiated species trapped with electrophiles, including but-1-ene oxide, leading to a new synthesis of 2-ethylchroman.     

Multiple lithium exchange under lithium cationization of cyclodextrins

Multiple lithium exchange is observed during electrospray ionization of alpha-, beta- and gamma-cyclodextrins from aqueous methanolic solution containing LiOH. Apart from [M + Li](+) and [M + nLi - (n - 1)H](+) ions, abundant multiply lithiated doubly charged ions corresponding to [M + nLi - (n - 2)H](2+) ions were observed. At least six lithium exchanges in alpha-cyclodextrin, seven in beta-cyclodextrin and eight in gamma-cyclodextrin were noted. The propensity of multiply lithiated doubly charged ions is much less in the open-ended maltoheptaose. It appears that during droplet or cluster formation and subsequent desolvation, LiOH trapped in the cavity of cyclodextrin reacts to form multiply lithiated ions. The singly charged [M + Li](+) and doubly charged [M + 2Li](2+) ions fragment by glycosidic cleavages, giving B series of ions, whereas the multiply lithiated ions fragment by cross ring cleavages ((2, 4)A or (O, 2)X) followed by glycosidic cleavage. From the tandem mass spectra, it appears that a maximum of two lithium exchanges occur in one sugar unit in these cyclodextrins.     

Thermal reactions of lithiated graphite anode in LiPF6-based electrolyte

The thermal reactions of a lithiated graphite anode with and without 1.3 M lithium hexafluorophosphate (LiPF₆) in a solvent mixture of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were investigated by means of differential scanning calorimetry (DSC). The products of the thermal decomposition occurring on the lithiated graphite anode were characterized by Fourier transform infrared (FT-IR) analysis. The lithiated graphite anode showed two broad exothermic peaks at 270 and 325 °C, respectively, in the absence of electrolyte. It was demonstrated that the first peak could be assigned to the thermal reactions of PF₅ with various linear alkyl carbonates in the solid electrolyte interphase (SEI) and that the second peak was closely related to the thermal decomposition of the polyvinylidene fluoride (PVdF) binder. In the presence of electrolyte, the lithiated graphite anode showed the onset of an additional exothermic peak at 90 °C associated with the thermal decomposition reactions of the SEI layer with the organic solvents.     

Synthetic approach to substituted cyclopropanes based on the coupling reaction of lithiated chloroalkyloxazolines with Fischer carbene complexes

Regioselective addition of lithiated oxazoline 2a, easily available from 2-(1-chloroethyl)-4,4-dimethyl-2-oxazoline 1a (LDA, THF, -98 degrees C), to alpha,beta-unsaturated Fischer carbene complexes 3 afforded cyclopropylcarbene complexes 4 as sole diastereoisomers. Exposure of carbene complexes 4a-c (M = Cr) to air and sunlight gave cyclopropane carboxylate derivatives 5a-c. A plausible mechanistic explanation is proposed. Moreover, when lithiated oxazoline 2b was generated from 1b in the presence of the carbene complex 3a,b, the oxazolinylcyclopropane carboxylates 6a,b formed as a 1:1 mixture of diastereoisomers. Chiral lithiated oxazoline 2c added regioselectively and diastereoselectively to chromium complexes 3a,b and to tungsten complexes 3d,e, leading, after oxidation of the metal fragment, to esters 7a,b with good diastereoselectivity (dr = 4:1). The reaction of lithiated oxazoline 2d with chromium complex 3b and tungsten complex 3e proceeded less diastereoselectively, furnishing, in both cases, after oxidation, the ester 7c as a 3:2 diastereoselective mixture.     

Structural determination of glycosphingolipids as lithiated adducts by electrospray ionization mass spectrometry using low-energy collisional-activated dissociation on a triple stage quadrupole instrument

Structural characterization of glycosphingolipids as their lithiated adducts using low-energy collisional-activated dissociation (CAD) tandem mass spectrometry with electrospray ionization (ESI) is described. The tandem mass spectra contain abundant fragment ions reflecting the long chain base (LCB), fatty acid, and the sugar constituent of the molecule and permit unequivocal identification of cerebrosides, di-, trihexosyl ceramides and globosides. The major fragmentation pathways arise from loss of the sugar moiety to yield a lithiated ceramide ion, which undergoes further fragmentation to form multiple fragment ions that confirm the structures of the fatty acid and LCB. The mechanisms for the ion formation and the possible configuration of the fragment ions, resulting from CAD of the lithiated molecular ions ([M + Li]+) of monoglycosylceramides are proposed. The mechanisms were supported by CAD and source CAD tandem mass spectra of various cerebrosides and of their analogous molecules prepared by H-D exchange. Constant neutral loss and precursor ion scannings to identify galactosylceramides with sphingosine or sphinganine LCB subclasses, and with specific N-2-hydroxyl fatty acid subclass in mixtures are also demonstrated.     

Structures of lithiated lysine and structural analogues in the gas phase: effects of water and proton affinity on zwitterionic stability

The structures of lithiated lysine, ornithine, and related molecules, both with and without a water molecule, are investigated using both density functional theory and blackbody infrared radiative dissociation experiments. The lowest-energy structure of lithiated lysine without a water molecule is nonzwitterionic; the metal ion interacts with both nitrogen atoms and the carbonyl oxygen. Structures in which lysine is zwitterionic are higher in energy by more than 29 kJ/mol. In contrast, the singly hydrated clusters with the zwitterionic and nonzwitterionic forms of lysine are more similar in energy, with the nonzwitterionic form more stable by only approximately 7 kJ/mol. Thus, a single water molecule can substantially stabilize the zwitterionic form of an amino acid. Analogous molecules that have methyl groups attached to either the N-terminus (NMeLys) or the side-chain amine (Lys(Me)) have proton affinities greater than that of lysine. In the lithiated clusters with a water molecule attached, the zwitterionic forms of NMeLys and Lys(Me) are calculated to be approximately 4 and approximately 11 kJ/mol more stable than the nonzwitterionic forms, respectively. Calculations of the potential-energy pathway for interconversion between the different forms of lysine in the lithiated complex indicate multiple stable intermediates with an overall barrier height of approximately 83 kJ/mol between the lowest-energy nonzwitterionic form and the most accessible zwitterionic form. Experimentally determined binding energies of water are similar for all these complexes and range from 57 to 64 kJ/mol. These results suggest that loss of a water molecule from the lysine complexes is both energetically and entropically favored compared to interconversion between the nonzwitterionic and zwitterionic structures. Comparisons to calculated binding energies of water to the various structures show that the experimental results are most consistent with the nonzwitterionic forms.     

Emerging Lithiated Organic Cathode Materials for Lithium-Ion Full Batteries

Organic electrode materials have application potential in lithium batteries owing to their high capacity, abundant resources, and structural designability. However, most reported organic cathodes are at oxidized states (namely unlithiated compounds) and thus need to couple with Li-rich anodes. In contrast, lithiated organic cathode materials could act as a Li reservoir and match with Li-free anodes such as graphite, showing great promise for practical full-battery applications. Here we summarize the synthesis, stability, and battery applications of lithiated organic cathode materials, including synthetic methods, stability against O₂ and H₂O in air, and strategies to improve comprehensive electrochemical performance. Future research should be focused on new redox chemistries and the construction of full batteries with lithiated organic cathodes and commercial anodes under practical conditions. This Minireview will encourage more efforts on lithiated organic cathode materials and finally promote their commercialization.     

Preparation and Characterization of 2,2′-Dipicolyl Diselenide and Their Derivatives

Lithium 2-picolylselenolate/tellurolate is obtained by reacting lithiated 2-picoline with elemental selenium/tellurium which upon aerial oxidation gives 2,2'-dipicolyl diselenide in case of selenium while 1,2-bis(2-pyridyl)ethane in case of tellurium. Condensation of 2-picolylselenolate anion with a variety of electrophiles provides a facile synthesis of 2-picolylalkyl selenides in good to excellent yields. Quenching of lithiated 2-picoline with 2,2'-dipyridyl diselenide gives mixed 2-picolylseleno pyridine in low yield. All the compounds prepared are new and have been characterized by elemental analysis, 1 H NMR, 13 C NMR and mass spectral studies.     

Benzimidazole nitrogen-directed, regiocontrolled, lithiation of ferrocenyl- and phenyl-N-n-butylbenzimidazoles

2-Ferrocenyl- and 2-phenyl-N-n-butylbenzimidazoles were synthesized to evaluate the influence of the benzimidazole functional group upon their directed lithiation. The regiochemistry of lithiation was studied, as well as the effect of stabilization of the lithiated species by diamine coordination using tetramethyl- ethylenediamine and (-)-sparteine. The lithiations were followed by reaction with a variety of electrophiles to give the disubstituted 2-ferrocenyl- and 2-phenyl-N-n-butylbenzimidazoles compounds. This study showed that despite a simple n-butyl function on the benzimidazole, directed lithiation was readily achieved with high regiocontrol on the ferrocenyl and phenyl groups. (-)-Sparteine failed to provide asymmetric induction in the ferrocene system, and its inefficiency is explained by intramolecular coordination of the lithiated species by the benzimidazole nitrogen, which is preferred over sparteine coordination.     

X-ray spectroscopy study of lithiated graphite obtained by thermal deposition of lithium

X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES), and near edge X-ray absorption fine structure (NEXAFS) spectroscopy are used for in situ studies of the electronic structure of lithiated natural graphite produced by thermal deposition of lithium upon graphite in a vacuum. By XPS and NEXAFS spectroscopy it is found that lithium vapor thermal deposition results in the formation of a lithiated graphite surface layer and a change in its electronic structure. Based on the quantum chemical simulation of the experimental СK_α XES spectrum of lithiated graphite, it is found that lithium atoms are located mostly on the edges of graphite crystallites. Atomic force microscopy reveals that the size of natural graphite flakes varies from 50 nm to 200 nm.     

Base-induced rearrangement of 1-trimethylsilylpropargyl alcohol. Generation of lithiated trimethylsiloxyallenes and their reactions

Under the effect of butyllithium, 1-trimethylsilylpropargyl alcohol undergoes rearrangement to afford the corresponding trimethylsiloxyallene or its lithiated one, which can be used for the preparation of α,β-unsaturated ketone derivatives.