Lithium In THF Research Articles

ChemInform Abstract: Synthesis and Some Reactions of a 2,2′‐Biphospholyl.

AbstractThe biphospholene (I) is converted to the biphosphole (III) by bromination and subsequent dehydrobromination.

Synthesis and some reactions of a 2,2′-biphospholyl

1,1′-Diphenyl-3,3′,4,4′-tetramethyl-2,2′,5,5′-tetrahydro-2,2′-biphosphole obtained by reductive dimerization of the appropriate phosphole has been converted into the corresponding 2,2′-biphosphole by P-bromination followed by dehydrobromination of the resulting P,P′-tetrabromo compound with α-picoline. This 2,2′-biphosphole gives two isomeric P-sulfides upon reaction with sulfur, and a Mo(CO) 4 chelate upon reaction with Mo(CO) 6. Cleavage of the two P-phenyl bonds by lithium in THF yields the corresponding biphospholyl anion, which is converted into a mixture of two isomeric bis(η 5,η 5-2,2′-diphosphafulvalene)diirons by treatment with FeCl 2. The reaction of Mn 2(CO) 10 in boiling xylene affords a mixture of three complexes, including a (η 5,η 5-2,2′-diphosphafulvalene)hexacarbonyldimanganese produced by thermal cleavage of the two PPh bonds. Under CO pressure there is a [1,5] P → C shift of the two phenyl groups, leading to formation of (η 5,η 5-3,3′-diphenyl-2,2′-diphosphafulvalene)hexacarbonyldimanganese.

A monodisperse Si-containing photoresist for a bilayer system

A monodisperse negative Si-containing photoresist (MAS) has been developed for use as the top imaging layer for a bilayer system. MAS is a formulation of poly(allyldimethylsilyl-α-methylstyrene) (PMA Si) and a bisazide. PMA Si was synthesized by anionic polymerization of the monomer with n-butyl lithium in THF at −78 °C. The polymer has a high softening point (Ts=164–166 °C) and a narrow molecular weight distribution (Mw=41 400, Mw/Mn=1.05). Near-UV-exposure has been carried out using a Kasper 2001 P contact printer. The Dig of MAS (0.2 μm in thickness) is 4.5 mJ/cm2 on a Si wafer and the γ value is over 2.0. The thickness reductions of MAS and MP-1300 have been measured under various O2-RIE conditions. The etching ratio of MP-1300/MAS ranges from 3:1 to 10:1 depending on conditions and is decreased with an increase in rf power and with a decrease in chamber pressure. Under the optimized development and O2-RIE condition, 0.75 μm line and space (L/S) patterns were accurately fabricated on the Si wafer having 0.5 μm high step. It is also noteworthy that 2.0 μm L/S patterns with a steep profile were obtained even in the MP-1300 layer of 4.0 or 6.0 μm in thickness.

An Improved Synthesis of Hexamethylphenalene

Abstract The synthesis of 1,3,4,6,7,9-hexamethylphenalene (2) has been improved from 15 steps to a four step procedure. The overall yield has been increased from an estimated 5% to 45%. Key steps in the synthesis are the reaction of 3,5-dimethylbenzylmagnesium chloride with 2,4-pentanedionato lithium in THF to make 5-(3,5-dimethyl-phenyl)-4-methyl-4-hydroxy-2-pentanone (5) and the Lewis acid acylation-alkation of 1,3,6,8-tetramethylnaphthalene using 3-chlorobutanoic chloride in hexane with sonication to make 1,3,4,6,7,9-hexamethyl-phenalane (2).

Synthesis of a stereoblock poly(methyl methacrylate)

AbstractThe sequential block copolymerization of diphenylmethyl methacrylate (DMA) and trityl methacrylate (TrMA), initiated by diphenyl methyl lithium in THF at ‐78°C followed by hydrolysis and methylation with diazomethane, leads to the formation of an isotacticsyndiotactic stereoblock poly(methylmethacrylate) (PMMA) of narrow molecular weight and block length distribution. Complete conversion of DMA is shown to be essential, since the presence of small quantities of this monomer during the polymerization of TrMA significantly lowers the isotactic content of this block. Polymerization times of at least 12 h were found to be necessary for complete polymerization of the TrMA.

Reduktive THF-spaltung durch lithiumsalze voluminöser silaethane; Intramolekulare cyclisierung CH- und NH-funktioneller verbindungen

The thermal LiHal elimination of ▪- and ▪ functional compounds provides a simple synthetic route to four-membered SiC and SiN rings. In attempts to inhibit dimerisation sterically, bulky silylmethyl and silylamino substituents were introduced (I–III). (Me 3Si) 3CSiF 2R reacts with LiNHR′, 1,3- migration of a silyl group from carbon to the nitrogen (I, R′= 2,4,6-Me 3C 6H 2) taking place. Substitution occurs for R′ = SiMe 2CMe 2, (II, III) only. Dichloro-bis(trimethylsilyl)methane reacts with halogenosilanes and lithium in THF to give bis(trimethylsilyl)-halogenosilaethanes (Me 3Si) 2CHSi(Hal)RR′; R= Me, R′ = N(SiMe 3) 2, IV, Hal = F; V, Hal = Cl. However a reductive THF cleavage accompanied by a silyl group migration to the oxygen occurs and 1-halogenosilyl-1- trimethylsilyl-5-trimethylsiloxi-pent-1-ene,(Me 3Si)(RR′SiHal)CCH(CH 2) 3OSiMe 3, Are The main products (VII–X) of these reactions. Disubstitution occurs with F 3Si-i-Pr (VI). (Me 3Si) 3CSiFNHSiMe 2CMe 3 (II) reacts with C 4H 9Li in a molar ratio 1 2 to give an 1-aza-2,3-disilacyclobutane (XI), involving substitution, LiF elimination, and nucleophilic migration of a methanide ion of the unsaturated precusor. (Me 3Si) 2CHSiFMeN (2,4,6-Me 3C 6H 2)SiMe 3 cyclizes under comparable conditions in the reaction with MeLi via a methylene group of the mesityl group (XII).

Diorganophosphinoalkyl-dimethylzinnchloride: Synthese, struktur und reaktionsverhalten

Phosphinoalkylchlorostannanes of the type Me 2Sn(Cl)(CH 2) n PR 1R 2 ( n = 2,3) (I–VIII) are synthesized by a redistribution reaction of the tetraorganostannanes Me 3Sn(CH 2) n PR 1R 2 ( n = 2,3) with trimethyltin chloride. In non-coordinating solvents the tin atom in I–IV is tetracoordinated, whereas NMR data indicate an intramolecular SnP interaction for V–VIII. In the solid state compound III exists as an 1:1 adduct with trimethyltin chloride. With methyl iodide compounds I–VIII form the phosphonium stannates Me 2S n Cl) (I) (CH 2) n P + R 1R 2Me (XI–XIII). Compounds I–VIII are suitable starting materials for the synthesis of the tin hydrides Me 2Sn(H)(CH 2) n PR 1R 2 (XIV–XVI) and the distannanes [Me 2Sn(CH 2) n PR 1R 2] 2 (XVII–XIX). The reaction of I–VIII with sodium in liquid ammonia or with lithium in THF, respectively, yields solutions of the corresponding alkali stannides Me 2Sn(M)(CH 2) n PR 1R 2 (M = Li, Na).

Comparison of the reactions of organic bromides and p-toluene sulphonates with polymeric anions

Alkyl bromides and tosylates were shown to react quantitatively with the living α-methylstyrene tetramer to yield the dialkyl adduct. Alkyl bromides also reacted with α-methylstyrene and lithium in THF to yield the dimeric adduct quantitatively, whereas only about 10% yield of this product was obtained with alkyl tosylate. This difference in behaviour was interpreted in terms of the different adsorptive powers of the two alkyl salts onto lithium metal. Aryl (phenyl) bromides and tosylates reacted with the tetramer to give only low (<5%) yields of the diaryl adduct and in both cases low molecular weight poly(α-methylstyrene) was produced. Benzene was also formed with phenyl bromide and the reaction was explained in terms of a transmetallation process. With the tosylate, the presence of phenol indicated that scission occurred at the SO 2Obond. The reactions of these reagents with α-methylstyrene and lithium in THF both yielded poly(α-methylstyrene) and phenyl bromide was quantitatively converted into biphenyl. Reactions controlled by competitive adsorption were invoked to explain these findings.

Electron spin resonance studies of spin-labelled synthetic polymers part 12. The polymerisation of methyl methacrylate initiated by butyl lithium

It is shown that poly(methyl methacrylate), polymerised at 0° or above by butyl lithium in THF or toluene, contains a number of n-butyl isopropenyl ketone units. The α-methylenic protons on the n-butyl group of these units can be abstracted by the propagating or other reactive carbanion to yield the carbanionic species ▪ This carbanion reacts with the “trap” 2-methyl-2-nitrosopropane to form, after hydrolysis and oxidation, the nitroxide label ▪ the e.s.r. spectrum of which comprises a triplet of doublets.

ORGANOLANTHANIDES AND ORGANOACTINIDES. IV. TRICYCLOPENTADIENYLPHENYLURANIUM(IV)

Abstract Tricyclopentadienylphenyluranium(IV) has been synthesized from Cp3U–Cl and phenyl lithium in THF and contains a U(IV)–carbon σ bond. Infrared and 1H NMR spectra support the presence of a phenyl group bound to uranium; proton assignments for the compound were confirmed from the spectrum obtained for tricyclopentadienyl-p-tolyluranium(IV) and a contact mechanism postulated to explain the shift of the ortho and para protons relative to the meta.

The Electron Paramagnetic Resonance Spectrum of the Phenalane Anion

The phenalane anion has been prepared by the reaction of alkali metals in ether solutions of both phenalane and phenalene. The electron paramagnetic resonance spectra of both the radical and of its ion pairs with sodium and with lithium in THF are reported. At room temperature there is an alternating linewidth involving the β protons caused by conformational interconversion of the axial and equatorial positions. At −80 °C the γ protons are not equivalent and the corresponding coupling constants are resolved.

Hexasubstituted disilanes from chlorosilanes and lithium in tetrahydrofuran

General procedures are provided for the preparation in satisfactory yields of hexamethyl-, hexaethyl- and 1,2-dibenzyl-1,1,2,2-tetramethyldisilane from the corresponding R 3SiCl compounds with lithium metal in THF. Optimal conditions for the preparation of hexamethyldisilane by this procedure were studied. Dimethylphenyl- and diethylphenylchlorosilanes gave the corresponding disilanes when treated with one equivalent of lithium in THF; no secondary cleavage of the SiSi bond occurred under these conditions. Diethylphenylsilyllithium was obtained by lithium cleavage of the corresponding disilane and characterized by reaction with chlorotriphenylsilane to give 1,1-diethyl-1,2,2,2-tetraphenyldisilane.