Search results for "Lithium"
showing 10 items of 680 documents
Stereoselectivity in the Addition of Organotitanium Reagents to Carbonyl Compounds
1986
Although great strides have been made in the area of stereoselective C—C bond forming reactions [1], many problems persist. Early studies concerning chemo- selective reactions of organotitanium reagents (Chapter 3) suggested that they might also behave stereoselectively in relevant cases. In fact, the first such observation goes back to 1979 when it was noted that dichlorodi- methyltitanium (2) adds to the ketone 1 in CH2C12 to produce a mixture of tertiary alcohols 4/5 instead of the desired (±) cuparene (3) [2, 3]. The striking aspect of this transformation is the high disastereoselectivity in favor of 4. Methyllithium shows the opposite stereoselectivity (4:5 = 34:66), in line with the s…
Reaction of lithium enediolates with perfluoroketene dithioacetals. Synthesis of α-trifluoromethyl γ-dicarboxylic acid derivatives
2004
The reaction of perfluoroketene dithioacetals with dianions of carboxylic acids proceeds through the substitution of the vinylic fluoride. The preparative value of this reaction depends strongly on the reaction and work-up conditions, the optimisation of which led to use LDA as a base and multiple extraction techniques. The overall process may be considered as a formal synthesis of α-trifluoromethyl γ-dicarboxylic acid derivatives.
Lithium intercalation chemistry, microstructure and superconductivity in zirconium and hafnium nitride halides
2000
Abstract Lithium intercalation in β-MNX (M=Zr, Hf; X=Cl, Br) leads to superconducting compounds with critical temperatures between 12 and 24 K. The lithium uptakes after treatment of the host materials with n-butyllithium/hexane solutions are ca. 0.2 atoms per formula for β-ZrNCl and β-ZrNBr, and between 0.07 and 0.67 for β-HfNCl. Electrochemical lithiation experiments agree with the results obtained with chemical methods, as samples with larger capacity on discharge are also those having larger lithium contents after chemical lithiation. Variations exist in the electrochemical profiles of different batches for the three compounds indicating differences in the intercalation reaction pathway…
Formation of arynezirconocenes from substituted diaryl bis (t-butylcyclopentadienyl) zirconium: application to the synthesis of new functionalizedort…
1991
The para-substituted diphenylzirconocenes [(t-BuCp)2Zr(p-C6H4R)2; R = Br, NMe2] (A) were easily obtained from the reaction of the appropriate organolithium reagent with bis(t-butylcyclopentadienyl)zirconium dichloride. Elimination of bromobenzene or N,N-dimethylaminobenzene from A by slight heating led to arynezirconocenes into which were inserted two equivalents of elementary chalcogens. As a result dichalcogenated zirconacycles [(t-BuCp)2ZrY2C6H3R; Y = S, Se] (B) were obtained. Complexes B constitute useful potential synthons in organic synthesis and a large family of new functionalized dichalcogenated benzenic compounds was prepared by reacting electrophiles. The structure of complexes B…
Zirconium and hafnium mono(alkyl) complexes containing a tridentate linked amido-tetramethylcyclopentadienyl ligand. Molecular structure of Hf(η5:η1:…
1998
Abstract Zirconium and hafnium complexes M( η 5 : η 1 : η 1 -C 5 Me 4 SiMe 2 NCH 2 CH 2 OMe)Cl 2 (M=Zr, Hf) containing the tridentate 2-methoxyethylamido-functionalized tetramethylcyclopentadienyl ligand C 5 Me 4 SiMe 2 NCH 2 CH 2 OMe have been synthesized by the reaction of the dilithium derivative Li 2 [C 5 Me 4 SiMe 2 NCH 2 CH 2 OMe] with MCl 4 (THF) 2 . Selective monoalkylation of the dichloro complexes gave complexes of the type M( η 5 : η 1 : η 1 -C 5 Me 4 SiMe 2 NCH 2 CH 2 OMe)(R)Cl (R=CH 2 Ph, o -C 6 H 4 CH 2 NMe 2 ). The crystal structure of the hafnium dichloro complex Hf( η 5 : η 1 : η 1 -C 5 Me 4 SiMe 2 NCH 2 CH 2 OMe)Cl 2 has been determined by X-ray crystal diffraction and sho…
C−C versus C−N Annulation Reactions of 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines: A Simple Synthesis of Novel 3-Aminoindene, Phthalimidine, Pyrr…
2001
The effect of various aromatic and aliphatic dielectrophiles on the lithium azaenolates of 2-alkyl-2-oxazolines and 2-alkyl-2-thiazolines has been examined. This effect varies greatly, depending on the nature of the dielectrophile used. 3-Aminoindene (3) and 3-alkylidenephthalimidine (4−5) derivatives were formed as a result of the reactions with dielectrophiles derived from ortho-substituted benzonitriles. Similarly, 2-alkylidenepyrrolidine (7) and 2-alkylidenepiperidine (8) derivatives were obtained in high yields from 2-alkyl-2-oxazolines or 2-alkyl-2-thiazolines and aliphatic dielectrophiles derived from ω-haloalkyldiphenylacetonitrile. C−C versus C−N annulation reactions are discussed.
ChemInform Abstract: C-C versus C-N Annulation Reactions of 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines: A Simple Synthesis of Novel 3-Aminoindene…
2010
The effect of various aromatic and aliphatic dielectrophiles on the lithium azaenolates of 2-alkyl-2-oxazolines and 2-alkyl-2-thiazolines has been examined. This effect varies greatly, depending on the nature of the dielectrophile used. 3-Aminoindene (3) and 3-alkylidenephthalimidine (4−5) derivatives were formed as a result of the reactions with dielectrophiles derived from ortho-substituted benzonitriles. Similarly, 2-alkylidenepyrrolidine (7) and 2-alkylidenepiperidine (8) derivatives were obtained in high yields from 2-alkyl-2-oxazolines or 2-alkyl-2-thiazolines and aliphatic dielectrophiles derived from ω-haloalkyldiphenylacetonitrile. C−C versus C−N annulation reactions are discussed.
Polyenolates of unsaturated carboxylic acids in synthesis. A straightforward synthesis of retinoic acids.
1990
Abstract Retinoic acids are prepared in a two step procedure by addition of lithium trienediolates of sorbic acid and 3-methyl-sorbic acid to β-ionone.
Polyenolates of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Unsaturated α-Amino Acids and β-Hydrazing Acids
1991
Abstract Regioselective reaction of lithium diene-and triene-diolates 1 and 2 with O-diphenylphosphinyl hydroxylamine affords unsaturated α-amino acids 3 and 4. Addition to DEAD leads selectively to γ-hydrazino unsaturated acids 5 and 6.
Lithium Ion Recognition with Nanofluidic Diodes through Host-Guest Complexation in Confined Geometries
2018
[EN] The lithium ion recognition is receiving significant attention because of its application in pharmaceuticals, lubricants and, especially, in energy technology. We present a nanofluidic device for specific lithium ion recognition via host guest complexation in a confined environment. A lithium-selective receptor molecule, the aminoethyl-benzo-12-crown-4 (BC12C4-NH2), is designed and functionalized on single conical nanopores in polyethylene terephthalate (PET) membranes. The native carboxylic acid groups on the pore walls are covalently linked with the crown ether moieties and the process is monitored from the changes in the current voltage (I-V) curves. The B12-crown-4 moieties are kno…