Equivalents Of Butyllithium Research Articles

Zirconocene-promoted synthesis of substituted tetrahydropyrans

Zirconocene reagents derived from zirconocene dichloride and two equivalents of butyllithium react with allylic, homoallylic diene ethers. Hydrolysis of the reaction products yields substituted tetrahydropyrans. The reaction is postulated to occur via cyclization of the diene to form a zirconacyclopentane. This cyclization occurs without allylic rearrangement.

Lithium complexes of tri- and hexaanionic cyclophosphazenates, the impact of metal coordination on the ring conformation

Cyclophosphazenes (RNH) 6P 3N 3 1 react with three and six equivalents of butyllithium in thf to give lithium complexes of tri- ( 2) and hexaanionic ( 3) phosphazenate ligands, respectively. A variety of lithium complexes 2 and 3 were prepared and structurally characterised. The degree of puckering of the (PN) 3 ring systems correlates with increasing ligand charge. The trianions solely exhibit the chair conformation; their deprotonated side groups are positioned at equatorial sites. This conformation ensures that the charge of the ligand is most effectively distributed and it also provides three distinct coordination sites for the three lithium ions. Complexes of the trianion can be monomeric or dimeric. Aryl-N(exo) derivatives tend to form monomers, while alkyl derivatives form dimeric sandwich complexes. Complexes of the hexaanion fall into two categories. Binary complexes, which contain the ligand and lithium ions, form dimers; the (PN) 3 ring in these complexes exhibit a chair conformation. Complexes which, in addition, contain small monodentate ions, such as chloride, fall into the second category; their ring systems adopt a boat conformation.

ChemInform Abstract: Olefin Hydrosilation Catalyzed by Zirconocene Complexes.

Abstract The hydrosilation of olefins such as styrene, 1-hexene, and 2-pentene with diphenylsilane can be carried out with catalysts generated from zirconocene dichloride and two equivalents of butyllithium. Complete regioselectivity is observed as only terminal organosilicon products are produced (∼ 90%). In the case of styrene, three major products are formed: diphenylphenethylsilane (77%), trans -1-diphenylsilyl-2-phenylethene (16%), and ethylbenzene (7%). The product distribution was found to be dependent on reagent concentrations: reactions run with excess diphenylsilane favored diphenylphenethylsilane; excess styrene favored trans -1-diphenylsilyl-2-phenylethene. Extensive H/D exchange is observed in the hydrosilation of styrene with Ph 2 SiD 2 .

ChemInform Abstract: N-Vinyl-, N-Allyl-, N-Propenyl- and N-Propargyl-benzotriazoles: Reactions of Their Lithium Derivatives.

1-Vinylbenzotriazole undergoes lithiation at the α-carbon and subsequent reactions with electrophiles to afford 1-(1-substituted vinyl)benzotriazoles (3a–d). Similarly, 1-(1-substituted propenyl)- (9a–c, 9e, 10a–c, 10e) and 2-(1-methylpropenyl)-benzotriazoles (14 and 15) were prepared by lithiation of the corresponding 1- and 2-propenyl-benzotriazoles followed by alkylation. 1- and 2-Allylbenzotriazoles 4 and 5 are also lithiated at the α-carbon and the intermediates react with electrophiles at this position. The structures of the propenyl derivatives were supported by an alternative synthetic route via rearrangements of the corresponding allyl isomers. 1-Propargylbenzotriazole (16) undergoes lithiation first at the acetylenic CH and then at the CH2 group. The dilithiated species, produced by treatment of 16 with two equivalents of butyllithium, reacts with an electrophile first at the carbon atom adjacent to the nitrogen atom, and then at the terminal carbon atom. Hence lithiation of 16 and subsequent reactions with electrophiles afford alkylated products 17a–d, 18a–d, 19a–b and 20a–c depending upon the amount of butyllithium and of the electrophile(s) used. The structures of each class of product were supported by spectral and analytical data.

1-Bromo-2-trifluoroacetylcyclobutenes as novel building blocks for the construction of trifluoromethyl substituted heterocycles. Part 1: Synthesis of 5-(trifluoromethyl)-2(5 H)-furanones condensed with substituted cyclobutenes

The regioselective reduction of substituted 1-bromo-2-trifluoroacetylcyclobutenes by lithium aluminium hydride affords corresponding brominated alcohols, which, under the treatment of two equivalents of butyllithium, give new lithiated cyclobutenes. Their carboxylation followed by lactonization induced by trifluoroacetic anhydride appeared to be an effective approach towards 5-trifluoromethylated furanones condensed with substituted cyclobutene rings.

Novel Generation of 3,3,3-Trifluoropropynyllithium and Transformation of the Carbonyl Adducts to Trifluoromethyl-Substituted Allenes

A novel method for the generation of 3,3,3-trifluoro­propynyllithium is reported, which involves treatment of trifluoromethyl-substituted enol tosylate, prepared from 1,1-dichloro-3,3,3-trifluoroacetone, with two equivalents of butyllithium. ­Palladium-catalyzed coupling reaction of sulfonates of the carbonyl adducts with organozinc reagents gave trifluoromethyl-containing tri- and tetrasubstituted allenes.

Direct Epimetallation of π‐Bonded Organic Substrates with Titanium(II) Isopropoxide: Intermediacy of Biradical, Oligomeric Titanium(II) Reagents

AbstractExtensive EPR experiments show that a titanium‐containing molecular triplet state is formed in solution by the reaction of two equivalents of butyllithium with one equivalent of titanium(IV) isopropoxide. At higher concentrations this product, titanium(II) isopropoxide, admixed with two equivalents of lithium isopropoxide, is accompanied by the formation of a variety of nontitanium‐containing side products. The powder EPR spectrum of the molecular triplet state in frozen solution is consistent with an asymmetric molecular chain of three Ti centers on which the unpaired electron centers are three metal atoms apart. Dilution experiments show that at lower concentrations, where the nontitanium‐containing side products have dissipated, the intensity of the molecular triplet spectrum varies approximately linearly with concentration. Thus there is no evidence that the observed triplet molecule is one component in a series of concentration‐dependent oligomerization steps. The bulky isopropoxy substituents and the coordination of the isopropoxide anions from the LiOiPr present appear to prevent closure of the Ti3 centers into an equilateral triangular diamagnetic structure. This steric hindrance, operative at the terminal diisopropoxytitanium centers and preventing closure to a ring, seems not to be observed with TiCl2·2THF, which is diamagnetic and may thus be expected to exist as an equilateral triangular cluster of three units of TiCl2·2THF, a structural model currently under further investigation. The smaller steric demand of the chloro and THF units would seem to permit octahedral coordination about each Ti center in such an equilateral trigonal array of Ti3 atoms. Chemical reactions carried out individually with diphenylacetylene, cis‐stilbene or cis‐stilbene oxide and titanium(II) diisopropoxide provide stoichiometric and stereochemical evidence that the attacking titanium(II) reagent is in fact the trimeric biradical. The role of the lithium isopropoxide byproduct in fostering the course of the previously reported SET reactions of titanium(II) isopropoxide and in determining the detailed structure of the open‐chain Ti trimer biradical has been explicated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Tert‐BuOK/BuLi‐Induced Facile Cyclodehydrogenation of Diphenyl Sulfide to Dibenzothiophene.

Attempted double ortho-lithiation of diphenyl sulfide using two equivalents of butyllithium in the presence of potassium tert-butoxide in diethyl ether-THF at room temperature under argon resulted in facile cyclodehydrogenation to afford dibenzothiophene in moderate yield.

Tert-BuOK/BuLi-Induced Facile Cyclodehydrogenation of Diphenyl Sulfide to Dibenzothiophene

Attempted double ortho-lithiation of diphenyl sulfide using two equivalents of butyllithium in the presence of potassium tert-butoxide in diethyl ether-THF at room temperature under argon resulted in facile cyclodehydrogenation to afford dibenzothiophene in moderate yield.

Asymmetric deprotonation—substitution of arenetricarbonylchromium(0) complexes: substituent controlled lithiation with the butyllithium–sparteine system

Attempted enantioselective deprotonation of fluorobenzenetricarbonylchromium(0) with ca. 1 equivalent of butyllithium/(−)-sparteine in ether–hexane at −78°C followed by a chlorotrimethylsilane quench gave the racemic ortho-substituted product. Analogous enantioselective deprotonation of anisoletricarbonylchromium(0), followed by electrophilic quench, gave the 1-(Rp)-substituted complexes in up to 77% yield with 27% e.e., but with methoxymethoxybenzenetricarbonylchromium(0), (4-triisopropylsilyloxymethyl)methoxymethoxybenzenetricarbonylchromium(0) and (N-t-butoxycarbonylaniline)tricarbonylchromium(0), the 1-(Sp)-products were formed in up to 58% yield with 92% e.e. The results are explained in terms of coordinative and non-coordinative enantioselective lithiation.

Organometallic Chemistry sans Organometallic Reagents: Modulated Electron‐Transfer Reactions of Subvalent Early Transition Metal Salts

AbstractThe potential of low‐valent, early transition‐metal reagents as selective reductants in organic chemistry has been foreshadowed by intensive research on the ill‐defined and heterogeneous subvalent titanium intermediates generated in the McMurry reaction and its numerous variants. As part of the long‐term research effort to develop soluble, well‐defined transition‐metal reductants of modulated and selective activity toward organic substrates, the THF‐soluble reductant, titanium dichloride, has been throughly examined, as well as the analogous ZrCl2 and HfCl2 reagents, all of which are readily obtainable by the alkylative reduction of the Group tetrachloride by butyllithium in THF. Noteworthy is that such interactions of MCl4 with butyllithium in hydrocarbon media lead, in contrast, to M(III) or M(IV) halide hydrides. Analogous alkylative reductions in THF applied to VCl4, CrCl3, and MoCl5 have yielded reducing agents similar to those obtained from Mcl4 but gradated in their reactivity. Such reductants have proved capable of coupling carbonyl derivatives, benzylic halides, acetylenes and certain olefins in a manner consistent with an oxidative addition involving a two‐electron transfer (TET). Such a reaction pathway is consistent with the observed stereochemistry of pinacol formation from ketones and for the reductive dimerization of alkynes. In contrast of the reaction of CrCl3 with two equivalents of butyllithium, which leads to a CrCl intermediate, the interaction of CrCl3 in THF with four equivalents of butyllithium at –78°C yields a reagent of the empirical formulation, LiCrH4.2LiCl.2 THF, as supported by elemental and gasometric analysis of its protolysis. This hydridic reductant cleaves a wide gamut of s̀ carbon–heteroatom bonds (C–X, C–O, C–S and C–N), towards which the CrCl reductant is unreactive. The type of cleavage and/or coupled products resulting from the action of “LiCrH4” on these substrates in best understood as arising from single‐electron transfer (SET). In light of the aforementioned findings, the gradated reducing action noted among TiCl2, HfCl2 and CrCl, as well as the contrasting reducing behavior between CrCl and LiCrH4, there is no doubt that future research with early transition metals will continue to yield novel reductants of modulated and site‐selective reactivity.

γ-Regioselective reaction of metaloxysilyl-substituted allyllithium derived from allyldiphenylsilanol

Treatment of allyldiphenylsilanol ( 1) with two equivalents of butyllithium in the presence of HMPA at −45°C afforded silylallyllithium 2a bearing an oxide anion on the silicon atom. The reaction of 2a with various electrophiles gave γ-products selectively in good yields. Higher regio- and stereoselectivities were achieved in the reaction of silyl-substituted allyllithium derived from potassium allylsilanolate with butyllithium.

A Straightforward Synthesis of Silylated and Stannylated Ynamines and Ynehydrazines

Metallated ynamines 5a-f and ynehydrazines 5g,h were prepared in a very short reaction sequence by consecutive treatment of trichloroethylene (1) with the lithium salt of secondary amines or of trimethylhydrazine, 2 equivalents of butyllithium and chlorotriorganosilanes or -stannanes.

New ethylene bridged monofluorenyl-amido group 4 complexes

9-[(2- t-Butylamino)ethyl] fluorene ( 1) was synthesized by the use of (1-chloro-2- t-butylamino)ethane ( 3) which provided convenient routes to 1 as well as 3-[(2- t-butylamino)ethyl] indene ( 7). Deprotonation of 1 with 2 equivalents of butyllithium followed by addition of ZrCl 4 or HfCl 4 led to [1-( η 1- t-butylamido)-2-( η 5-9-fluorenyl)ethane] zirconium ( 8) and hafnium ( 9) dichloride, respectively. Complexes 8 and 9 when activated with methylaluminoxane (MAO) are active catalysts for the polymerization of ethylene.

Butyllithium Mediated Cyclization of Substituted cis-1-(Alk-4-ynyl)-2-hydroxymethyl-1-iodocyclopropanes: Synthesis of Functionalized Spiro[2.4]heptanes

Upon treatment with 2.2 equivalents of butyllithium in diethyl ether (-78°C to r.t.), the substituted iodocyclopropanes 4-6 and 8 are transformed into the functionalized spiro[2.4]heptanes 9-11 and 13, respectively.

Übergangsmetall-Silyl-Komplexe: IL. Darstellung eines Cyclopentadienylrhodium-bis(carben)-Komplexes aus Li[Cp★Rh(H)(SiMe 3) 2

Zusammenfassung Reaction of Cp★Rh(H)2(SiMe3)2 with two equivalents of butyllithium in THF, followed by addition of N-methyl- 2-chlorpyridinium tetrafluoroborat gives the bis(carbene) complex Cp★Rh(CNMeCHCH)2. A mechanism is proposed involving a sequence of deprotonation, substitution and Me3SiCI elimination steps, starting with the known anionic complex Li[Cp★Rh(H)(SiMe3)2].

N‐Vinyl‐, N‐Allyl‐, N‐Propenyl‐ and N‐Propargyl‐benzotriazoles: Reactions of Their Lithium Derivatives

Abstract1‐Vinylbenzotriazole undergoes lithiation at the α‐carbon and subsequent reactions with electrophiles to afford 1‐(1‐substituted vinyl)benzotriazoles (3a–d). Similarly, 1‐(1‐substituted propenyl)‐ (9a–c, 9e, 10a–c, 10e) and 2‐(1‐methylpropenyl)‐benzotriazoles (14 and 15) were prepared by lithiation of the corresponding 1‐ and 2‐propenyl‐benzotriazoles followed by alkylation. 1‐ and 2‐Allylbenzotriazoles 4 and 5 are also lithiated at the α‐carbon and the intermediates react with electrophiles at this position. The structures of the propenyl derivatives were supported by an alternative synthetic route via rearrangements of the corresponding allyl isomers. 1‐Propargylbenzotriazole (16) undergoes lithiation first at the acetylenic CH and then at the CH2 group. The dilithiated species, produced by treatment of 16 with two equivalents of butyllithium, reacts with an electrophile first at the carbon atom adjacent to the nitrogen atom, and then at the terminal carbon atom. Hence lithiation of 16 and subsequent reactions with electrophiles afford alkylated products 17a–d, 18a–d, 19a–b and 20a–c depending upon the amount of butyllithium and of the electrophile(s) used. The structures of each class of product were supported by spectral and analytical data.

Olefin hydrosilation catalyzed by zirconocene complexes

The hydrosilation of olefins such as styrene, 1-hexene, and 2-pentene with diphenylsilane can be carried out with catalysts generated from zirconocene dichloride and two equivalents of butyllithium. Complete regioselectivity is observed as only terminal organosilicon products are produced (∼ 90%). In the case of styrene, three major products are formed: diphenylphenethylsilane (77%), trans-1-diphenylsilyl-2-phenylethene (16%), and ethylbenzene (7%). The product distribution was found to be dependent on reagent concentrations: reactions run with excess diphenylsilane favored diphenylphenethylsilane; excess styrene favored trans-1-diphenylsilyl-2-phenylethene. Extensive H/D exchange is observed in the hydrosilation of styrene with Ph 2SiD 2.

Butyllithium-induced dimerization of pent-3-en-1-yne and related additions

The enynes HCCCHCHCH 2R (R  H, Me, OMe, NMe 2 SMe), are converted into dimers by treatment with slightly more than two equivalent of butyllithium. The Zconfiguration predominates in the dimers obtained after aqueous workup. The lithiated enynes (R  H, Me, SMe) and acetylenic compounds LiCCCH 2R (R  SMe, C 6H 5) add in an analogous way to the double bond of LiCCCHCH 2.

Palladium-Catalyzed Coupling of (1,3-Butadiynyl)amines with Aryl and Vinyl Iodides

4-Aryl, 4-heteroaryl- and 4-vinyl substituted (1,3-butadiynyl)-amines 7 and 8 are prepared in a one-pot synthesis by the successive treatment of the (3,4,4-trichloro-3-buten-1-ynyl)amines 1 with two equivalents of butyllithium and zinc chloride and by the palladium- catalyzed cross-coupling of the resulting aminobutadiynylzinc chlorides 4 with alkenyl, aryl and heteroaryl iodides, respectively