Dilithium Reagent Research Articles

ChemInform Abstract: Control of Site of Lithiation of 3‐(Aminomethyl)pyridine Derivatives.

Lithiation of N-(pyridin-3-ylmethyl)pivalamide, tert-butyl N-(pyridin-3-ylmethyl)carbamate, and N,N-dimethyl-N′-(pyridin-3-ylmethyl)urea with tert-butyllithium (3 equiv) in anhydrous tetrahydrofuran at –78 °C takes place on the nitrogen and on the ring at the 4-position. The dilithium reagents thus obtained react with various electrophiles to give the corresponding substituted derivatives in high yields. On the other hand, regioselective side-chain lithiation occurs with lithium diisopropylamide (3.3 equiv) at –20 to 0 °C. A mixture of ring and side-chain substitution products is obtained with n-butyllithium as the lithium reagent. Treatment of one of the ring-substituted products with trifluoroacetic anhydride in dichloromethane under reflux conditions led to formation of the corresponding 1H-pyrrolo[3,4-c]pyridine in high yield.

Directed Lithiation of N′-[2-(4-Methoxyphenyl)ethyl]-N,N-dimethylurea and tert-Butyl [2-(4-Methoxyphenyl)ethyl]carbamate

N ′-[2-(4-Methoxyphenyl)ethyl]- N , N -dimethylurea and tert -butyl [2-(4-methoxyphenyl)ethyl]carbamate are doubly lithiated on the nitrogen and ortho to the directing metalating group at –20 to 0 °C with three mole equivalents of n -BuLi in anhydrous THF. Reactions of the dilithium reagents produced in situ with various electrophiles give high yields of the corresponding substituted products. In the case of the urea, side-products due to lithiation and substitution on one of the methyl groups of the urea unit are obtained in low yields (0–17%).

Control of Site of Lithiation of 3-(Aminomethyl)pyridine Derivatives

Lithiation of N-(pyridin-3-ylmethyl)pivalamide, tert-butyl N-(pyridin-3-ylmethyl)carbamate, and N,N-dimethyl-N′-(pyridin-3-ylmethyl)urea with tert-butyllithium (3 equiv) in anhydrous tetrahydrofuran at –78 °C takes place on the nitrogen and on the ring at the 4-position. The dilithium reagents thus obtained react with various electrophiles to give the corresponding substituted derivatives in high yields. On the other hand, regioselective side-chain lithiation occurs with lithium diisopropylamide (3.3 equiv) at –20 to 0 °C. A mixture of ring and side-chain substitution products is obtained with n-butyllithium as the lithium reagent. Treatment of one of the ring-substituted products with trifluoroacetic anhydride in dichloromethane under reflux conditions led to formation of the corresponding 1H-pyrrolo[3,4-c]pyridine in high yield.

Two Versatile and Parallel Approaches to Highly Symmetrical Open and Closed Natural Product‐Based Structures

Two parallel approaches for preparing diverse and highly symmetrical homohybrids derived from a series of mono- and diterpenes, steroids, and alkaloids are reported. Both procedures are based on the mono-addition of bis(alkynyl) dilithium reagents to natural products having a carbonyl group to produce the corresponding alkynyl derivatives. The Glaser-Hay Cu-promoted homocoupling of these alkynyl natural product mono-adducts as well as the Huisgen Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction resulted in the synthesis of steroid-, terpene-, and alkaloid-based homohybrid derivatives incorporating diverse spacers to join the natural product scaffolds. Straightforward entries to novel closed highly symmetrical and complex estrone-based macrocyclic and cage architectures by means of the Glaser-Eglinton homocoupling and the CuAAC reaction have been devised.

Homologues of N-heterocyclic carbenes: Detection and electronic structure of N-bridgehead pyrido[ a]-anellated 1,3,2-diazagermol-2-ylidenes

Novel N-bridgehead pyrido[ a]-anellated 1,3,2-diazagermol-2-ylidenes 1a, b were obtained from GeCl 2 · dioxane and dilithium reagents formed from N- tert-butyl pyridine-2-aldimines and excess lithium in THF whereas attempts to generate the analogous silylene by reduction of the dichloro-pyrido[ a]-1,3,2-diazasilole 4a, synthesized from SiCl 4 and the new dilithium reagent, failed. Characteristic chemical shifts of the pyrido 1H and 13C nuclei between those of pyridine compounds and the not fully cyclodelocalized electron-rich 4a with dihydropyridine substructure hint to a cyclodelocalized 10π electron system in 1a, b. Quantum chemical investigations of a series of pyrido[ a]- and benzo-anellated imidazol-2-ylidenes and their silylene and germylene homologues show for all compounds cyclodelocalized 10π-systems but for pyrido[ a]-anellation an increase of the energy of the π-MO’s relative to those of element(II) lone electron pairs which leads to destabilization compared to the benzo-anellated isomers.

Synthetic and Structural Investigations on Double- and Single-Butterfly Fe/E (E = S, Se) Cluster Complexes Containing Diselenolate Ligands

The first examples of diselenolate ligand-containing butterfly Fe/E (E = S, Se) complexes are now reported. When ca. 1 equiv of dilithium reagent 4-LiC6H4C6H4Li-4‘ containing n-BuBr (prepared from ...

Partially fluorinated naphthalene derivatives from 1,4-dilithio-1,3-dienes and C 6F 6

Multi-substituted partially fluorinated aromatic compounds, such as naphthalene derivatives could be readily prepared by the reaction of 1,4-dilithio-1,3-dienes with hexafluorobenzene via double nucleophilic substitution. When these dilithium reagents were treated with hexachlorobenzene, chloropentafluorobenzene or bromopentafluorobenzene, chlorine–lithium or bromine–lithium exchange reactions, instead of nucleophilic substitution, took place.

A Simple Procedure for the Side-Chain Substitution of 2-Alkyl-3 H -quinazo­line-4-thiones: Application in Synthesis

Double lithiation of 2-alkyl-3H-quinazoline-4-thiones at nitrogen and at the α-hydrogen of the 2-alkyl group (Me, Et, Pr) has been achieved with n-butyllithium at -78 °C in anhydrous THF under nitrogen. Reactions of the dilithium reagents obtained with various electrophiles (iodomethane, iodoethane, 1-bromobutane, D2O, benzaldehyde, 4-anisaldehyde, butan-2-one, cyclohexanone, benzophenone, phenyl isothiocyanate, tetraisopropylthiuram disulfide) gave the corresponding modified 2-substituted 3H-quinazoline-4-thiones 4-22 in excellent yields.

A Convenient Procedure for the Synthesis of Novel Modified 3-Substituted 1H-Quinoxaline-2-thiones via Side-Chain Lithiation of 3-Alkyl-1H-quinoxa­line-2-thiones

3-Methyl-1H-quinoxaline-2-thione (1) has been doubly lithiated, at nitrogen and at the 3-methyl group, with n-butyllithium at –78 °C in THF. The resulting dilithium reagent obtained reacts with a variety of electrophiles (iodomethane, iodoethane, 1-bromobutane, D2O, benzaldehyde, anisaldehyde, 2-hexanone, cyclohexanone, benzophenone, phenyl isothiocyanate) to give the corresponding modified 3-substituted 1H-quinoxaline-2-thiones 4–13 in high yields. Similarly, double lithiation of 3-ethyl- (4) and 3-propyl-1H-quinoxaline-2-thiones (5), followed by reaction with some electrophiles gave the corresponding modified 3-substituted derivatives 15–19 in high yields. Treatment of some of the products with trifluoroacetic acid in dichloromethane at room temperature led to formation of substituted 2,3-dihydrothieno[2,3-b]quinoxalines in good yields.

Lithiophenylalkyllithiums: new dilithium reagents having both sp 2- and sp 3-hybridised remote carbanionic centres

The reaction of chloro-(2-chloroethyl)benzenes ( 1), 4-chloro-(3-chloropropyl)benzene ( 3) or 4-chlorophenyl chloromethyl ether ( 5) with lithium power using naphthalene as the electron shuttle (8 mol%) in the presence of different carbonyl compounds [Bu t CHO, PhCHO, Me 2CO, Et 2CO, (CH 2) 5CO, PhCOMe] in THF at −78 to 20 °C gives, after hydrolysis with water, the expected diols 2, 4 or 6, respectively. Bromo-2-(chloroethyl)benzenes ( 7) are treated with n-BuLi in THF at −100 °C, so the corresponding bromine–lithium exchanges takes place giving an intermediate, which is trapped by treatment with benzaldehyde or cyclohexanone, affording intermediates 9, which are submitted to a naphthalene-catalysed (8 mol%) lithiation with lithium power as above, followed by reaction with 3-pentanone and final hydrolysis with water, to give differently substituted diols 10. Some diols 2 are transformed into either the corresponding oxepane 11 or dienes 12 under Mitsunobu type conditions or by acidic treatment, respectively.

High oxidation state imido metallasiloxanes: synthesis and structural characterisation of novel bis-imido chromium(VI) and molybdenum(VI) compounds †

For reactions between [M(NBut)2Cl2] (M = Cr or Mo) or [Mo(NAr)2Cl2]·dme, Ar = 2,6-Pri2C6H3, dme = 1,2-dimethoxyethane, and tetraphenyldisiloxanediol, [O(Ph2SiOH)2] (2∶1), in the presence of a nitrogen donor base, changing the nitrogen donor from pyridine, py, to triethylamine, NEt3, inhibited the protonation of imido groups and facilitated the formation of bis-imido compounds. Thus the compounds [Cr(NBut)2(O(Ph2SiO)2)]21, [Mo(NBut)2(O(Ph2SiO)2)2] 2 and [Mo(NAr)2(O(Ph2SiO)2)]23 were isolated when NEt3 was used as base. Compound 3 was also formed when the dilithium reagent [O(Ph2SiOLi)2] was used. The pyridine adduct [Mo(NAr)2Cl2]·2py 4 was isolated from the reaction between [Mo(NAr)2Cl2] and O(Ph2SiOH)2 and py (1∶1∶2 molar ratio). Compounds 2, 3·C6H6 and 4·0.5C6H5Me have been characterised by X-ray crystallography. The dimeric composition of 1 in the gas phase and in benzene was confirmed by mass spectroscopy and cryoscopic molecular weight determination respectively. All compounds were characterised by NMR spectroscopy.

Synthesis and Application of Ring‐Substituted Analogues of the [4‐(η‐Cyclopentadienylidene)‐4,7,7‐trimethyl‐4,5,6,7‐tetrahydro‐η5‐indenyl]‐ZrCl2 Ansa‐Metallocene System

AbstractReaction of the 2,5‐hexanedione‐derived bisfulvene 1 with RLi reagents (R = phenyl or n‐butyl) yields the ring‐closed [4‐(cyclopentadienylidene)‐7‐R‐4,7‐dimethyl‐4,5,6,7‐tetrahydroindenyl]dilithium reagents 3. Their reaction with MCl4 (M = Ti, Zr, Hf) gives the corresponding ansa‐group‐4‐metallocene dichloride complexes 4, 6, or 7. In a similar way the [7‐allyl‐4‐(η‐cyclopentadienylidene)‐4,7‐dimethyl‐4,5,6,7‐tetrahydro‐η5‐indenyl]metal dihalides (M = Ti, Zr) (6d, 4d) are prepared. Two diastereomers are formed in most cases, some of which could be separated. The five representative examples cis‐ and trans‐4c, trans‐4d, cis‐6c, and trans‐7c of these complexes were characterized by X‐ray diffraction. All these six‐membered ring‐annulated C1‐bridged ansa‐metallocene dichlorides exhibit extremely small D1ZrD2 angles (D1 and D2 denote the centroids of the cyclopentadienyl rings) of 116.5°, i.e., they are characterized by a very open bite of the bent metallocene wedge. The homogeneous Ziegler‐type catalysts derived from these ansa‐zirconocenes by activation with methylalumoxane have high activities and all produce low‐molecular mass atactic polypropylenes or propene oligomers.

Organometallic chemistry of chromium(VI): synthesis of chromium(VI) alkyls and their precursors. X-ray crystal structure of the metallacycle Cr(NBu-tert)2{o-(CHSiMe3)2C6H4}

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOrganometallic chemistry of chromium(VI): synthesis of chromium(VI) alkyls and their precursors. X-ray crystal structure of the metallacycle Cr(NBu-tert)2{o-(CHSiMe3)2C6H4}Nicolaas Meijboom, Colin J. Schaverien, and A. Guy OrpenCite this: Organometallics 1990, 9, 3, 774–782Publication Date (Print):March 1, 1990Publication History Published online1 May 2002Published inissue 1 March 1990https://doi.org/10.1021/om00117a037RIGHTS & PERMISSIONSArticle Views503Altmetric-Citations80LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Some reactions of the ethylenebis(phenylphosphido)dilithium reagent [{Li(THF) 2} 2(PhPCH 2CH 2PPh)] 2, and its X-ray Structure

Some reactions of the ethylenebis(phenylphosphido)dilithium reagent [{Li(THF) 2} 2(PhPCH 2CH 2PPh)] 2, and its X-ray Structure

Lithium pentaalkyl/aryl stannate complexes as intermediates in the lithium-tin exchange reaction

Abstract

ChemInform Abstract: The Synthesis of Metallaindene and Metallafluorene Compounds.

AbstractAusgehend von Diphenylacetylen (I) bzw. Dibromdiphenyl (XIII) werden gemäß Schema die Metallaindene (III)‐(V) sowie (XII) bzw. die Metalla?uorene (XIV) und (XV) synthetisiert.

The Synthesis of Metallaindene and Metallafluorene Compounds

Abstract The synthesis, spectra and properties of a series of metallaindenes (benzometalloles) and metallafluorenes (dibenzometalloles) have been investigated. Improved procedures for the formation of 1-lithio-1-phenyl-2-n-butyl-2-(2′-lithiophenyl)ethene from a reaction between n-butyllithium and diphenylacetylene have been achieved. Reactions of this dilithium intermediate with dimethyl- and diphenyldichlorosilane have afforded the respective benzosiloles in good yield. Reactions of the dilithium reagent with either dimethyltin dichloride or phenyldichlorophosphine produce the respective benzostannole and benzophosphole, whereas reactions with MCl4 (M = Si, Ge, Sn) result in formation of the corresponding metallacycles. Treatment of the benzophosphole with (n5-C5H5)Co(CO)2 or Fe3(CO)12 affords new organocobalt and -iron complexes which contain the benzophosphole ligand. The dilithium intermediate 1-lithio-1,2-diphenyl-2-(2′-lithiophenyl)ethene, prepared from phenyllithium and diphenylacetylene, reacts wi...

Die oxidative Addition von NickeI(0)-KompIexen an Kohlenstoff-Kohlenstoff-Bindungen im Cyclobutadien. Zur Frage der Überführbarkeit von Cyclobutadien-Nickel(O)-Komplexen in Nickelaringe / Oxidative Addition of Nickel(O) Complexes to Carbon-Carbon Bonds in Cyclobutadiene. The Question of the Interconvertibility of Cyclobutadiene-nickel(O) Complexes and the Nickelaring Systems

Abstract Bis(triethylphosphine)(η4-tetraphenylcyclobutadiene)nickel (4) was synthesized by the reduction of (η4-tetraphenylcyclobutadiene)nickel(II)bromide (3) with t-butyllithium in the presence of Et3P, and its structure was determined by X-ray crystallography. Furthermore, its reactivity towards CO, CH3CO2H, PhC≡CPh, LiAlH4 and O2 were investigated. 1,1-Bis(triethylphos-phine)-2,3,4,5-tetraphenylnickelole (14) was synthesized from (E,E)-1,4-dilithio-1,2,3,4-tetraphenyl-1,3-butadiene (15) and bis(triethylphosphine)nickel(II)bromide. Since the resulting crystals of the nickelole were not suitable for X-ray structure determination, the compound was characterized by elemental analyses, spectral data and carbonylation to yield tetraphenylcyclo-pentadienone (6). Analogous reductions of (η4 -tetraphenylcyclobutadiene)nickel(II)bromide (3) in the presence of Ph3P or Ph2PCH2CH2PPh2 , followed by carbonylation, led to 6 in 40% yield, demonstrating that about half of the cyclobutadiene rings in 3 undergo cleavage upon reduction to give the nickelole. Reactions of the dilithium reagent 15 with NiBr2 complexed with Me2PCH2CH2PMe2 ,Ph3P or Et2PCH2CH2PEt2 , led to the formation of thermolabile nickeloles, as demonstrated by carbonylàtion which yielded 6. Warming of the nickeloles and subsequent treatment with CH3CO2H led to the formation of 1,2,3,4,5,6,7,8-octaphenyl-1,3,5,7-octatetraene (8) and, in one case, octaphenyl-cyclooctatetraene (5). The relevance of these findings to the mechanism of the Reppe nickel-catalyzed oligomerization of alkynes is discussed.

Macrocycles containing tin. Syntheses of symmetrical macrocycles containing two or four diphenylstanna units

Abstract : The syntheses of macrocycles containing two diphenylstanna moieties, cyclo-(Ph2Sn(CH2)n-)2 (1, n = 4, 5, 6, 8, 10, 12), and four diphenylstanna moieties, cyclo-(Ph2Sn(CH2)n (-)4 (2, same n), are reported. Alpha, omega-bis (Bromomagnnesio)al-kanes reacted with Ph3SnC1 to give alpha, omega-bis(triphenylstannyl)alkanes which upon treatment with HBr gave alpha, omega-bis (bromodiphenylstannyl)alkanes (4). Compounds 4 reacted with the corresponding chain length alpha, omega-bis(bromomagnesio)alkanes to give 1 and 2. Alternatively, good yields of 1 (n = 4, 5, 6, 8) were obtained by converting 4 to dilithium reagents (7) which were allowed to react with alpha, omega-dibromoalkanes. Good yields of 2 (n = 4, 5, 6) were obtained by first treating 4 with C1(CH2) MgBr to give dichlorides which were then allowed to react with 7 in a second step. Purifications of the macrocyles and several synthetic intermediates were effected by preparative reverse phase chromatography. The macrocyclic products were characterized by NMR spectroscopy, molecular weight determinations and elemental analyses.

ChemInform Abstract: PREPARATION AND PROPERTIES OF METALLACYCLOPENTANE AND DINEOPENTYL DERIVATIVES OF MOLYBDENOCENE AND TUNGSTENOCENE. X‐RAY CRYSTAL AND MOLECULAR STRUCTURE OF BIS(η‐CYCLOPENTADIENYL)MOLYBDENACYCLOPENTANE

AbstractWährend die Reaktion der Molybdocendihalogenide (I) (beste Ausb. mit Iodiden) mit (II) die Derivate (III) liefern, können W‐Analoge nicht auf diese Art dargestellt werden.