Ethylene lithium hydride

A synthesis of comblike organoboron polymer/boron stabilized imidoanion hybrids was examined via reactions of poly(organoboron halides) with 1-hexylamine and oligo(ethylene oxide) monomethyl ether and subsequent neutralization with lithium hydride (scheme 8). The obtained polymers (10) were amorphous soft solids soluble in common organic solvents such as methanol, THF, and chloroform. In the nB-NMR spectra (Fig. 11), neutralization of the iminoborane unit with lithium hydride... 

Starting with l,l-bis(trimethylsilyl)ethylene (5) in hexane or diethyl ether as the solvent we obtained another dimeric product, a monolithiumorganic compound 8 which was shown not to be formed by lithium hydride elimination from the 1,4-dilithiobutane derivative 6, the only product in THF as the solvent. Obviously the vinyllithium derivative 7, primarily formed in the same manner as vinyllithium from ethylene [4], in contrast to vinyllithium [4] does not add further lithium atoms but adds itself to the starting material 5 yielding 8 ... 

Lead(II,IV) oxide Lithium hydride Magnesium Same as for lead dioxide Nitrous oxide, oxygen Air, beryllium fluoride, ethylene oxide, halogens, halocarbons, HI, metal cyanides, metal oxides, metal oxosalts, methanol, oxidants, peroxides, sulfur, tellurium... 

During my time in Heidelberg, that is, earlier than 1936, we found, in the course of experiments to distill butyllithium under high vacuum, that the lithium alkyl smoothly decomposed into lithium hydride and 1-butene. In carrying out similar experiments with ethyllithium immediately after the war, Gellert and I (41) found firstly that the lower lithium alkyls were distillable under suitable conditions, and secondly that 1-butene was formed from ethylene in contact with ethyllithium. From this observation it was a very short step to discover the stepwise organometallic synthesis (42)... 

These experimental measurements have prompted ab initio MO calculations of model additions of lithium hydride (Houk et al., 1985). With ethylene, monomeric lithium hydride initially forms a stable rc-complex [7], which passes through a four-centre cyclic transition structure [8] to yield the ethyllithium [9], with energies relative to reactants of-50.0, 28.5, and... 

The course of these additions of lithium hydride resembles that found for the addition of borane (Nagase et al., 1980 Graham et al., 1981). With ethylene, the initial step is exothermic formation of a Jt-complex without barrier, then rate-determining transformation to the borane via a four-centre transition structure. In both the borane and lithium hydride additions, there is relatively little development of the new C—H bond with distances of 1.692 and 1.736 A respectively in the transition structures. When a carbanionic product is not formed, for example in the reaction of lithium hydride with cyclopropenyl cation yielding cyclopropene and lithium cation (Tapia et al., 1985), reaction again occurs via a hydride-bridged complex, but the C- H- -Li array remains nearly linear throughout the reaction. 

Whereas pure lithium hydride prepared from lithium and H2 does not add to C=C double bonds, the lithium hydride bond in 22 proves to be more reactive, for example, with norbomene, propylene, or ethylene. 

With the purpose of employing a more soluble form of complexed lithium hydride in such a process, Ziegler and Gellert heated ethylene in ether under pressure at 120-140 °C with LAH, which had been prepared for the first time by Schlesinger and coworkers. To Ziegler s gratification LAH was smoothly converted into lithium tetraethylaluminate (10), which could be isolated in high yield as a crystalline adduct. As proof of structure, the same adduct was also synthesized by the admixture of the lithium and aluminum ethyl derivatives in a 1 1 ratio (Scheme 2). This study represents the first authenticated instance of hydroalumination. 

Other bases may be employed, e.g. lithium hydride, sodium hydride, sodium amide or sodium in ethylene glycol with sodium in ethylene glycol, the reaction is called the Bamford-Stevens reaction. Aldehyde tosylhydrazones (200) do not form dianions with organolithiums, but the reagent adds to the carbon-nitrogen double bond to give the dilithium derivative (201) which decomposes to the organolithium compound (202). 

Monomeric 1,2-dilithioethane 1 should thus be marginally unstable thermodynamically toward dissociation into ethylene and Li2, but stable toward the loss of lithium hydride or of hydrogen. Equation 2, however, is not in agreement with experimental results of Rautenstrauch and Bogdanovic who found that 1,2-dilithioethane 7 — if it is formed at all by the addition of lithium to ethylene — looses lithium hydride spontaneously. These findings prompted a reconsideration of the nature of 1,2-dilithioethane 7 and its tendency to eliminate lithium hydride >. Most interestingly it was found that the vinyllithium-lithium hydride complex 10 is... 

Reaction 1 appears to result solely in termination. In hydrogenolysis experiments with various chelates we have observed precipitation of lithium hydride in all cases at room temperature. Attempts to generate chelated LiH in situ by adding hydrogen during ethylene polymerization also caused a rapid, irreversible loss of activity. Since there is no evidence that lithium hydride can add to ethylene under moderate polymerization conditions, it is unlikely that any significant chain transfer occurs via this mechanism. Potassium alkyls readily eliminate olefin with the formation of metal hydride, and sodium alkyls do so at elevated temperatures (56). It was noted earlier that chelation of lithium alkyls makes them more like sodium or potassium compounds, so it is quite probable that some termination occurs by eliminating LiH. It is conceivable that this could be a chain transfer mechanism with more reactive monomers than ethylene because addition to lithium hydride would be more favorable. 

The addition of metal and metalloid hydrides to carbon-carbon double bonds is not a new reaction, having been observed from time to time with silanes of the type R3SiH under free-radical conditions (4%, 85) and with boron hydrides (68). The versatility of such hydride-olefin interactions, nevertheless, first became evident with the recent researches of Ziegler with lithium and aluminum alkyls (139). The observation that attempted distillation of ethyllithium led to decomposition into lithium hydride, ethylene, and higher olefins prompted the following formulation of the reaction course (see 18) ... 

Houk, Schleyer, and co-workers studied the nucleophilic additions of lithium hydride and methyllithium to acetylene and ethylene, respectively [135, 136]. The best estimate of the activation energy from Schleyer s study is 3 kcal/mol for the reaction of acetylene with lithium hydride. There is a negligible difference in the calculated activation energies of the acetylene-LiH and ethylene-LiH reactions, although acetylene appears to form a weaker n-complex with LiH than ethylene does. The competitive deprotonation processes were also considered by these and other workers [137]. 

Because the reaction of lithium hydride with ethylene was too slow, he substituted the more reactive lithium aluminum hydride. Subsequently, he found that triethylaluminum added to ethylene produced a higher molecular weight trialkylaluminum. This reaction which was investigated by his former student H. Gellert was appropriately called the aufbau or build up" reaction. 

Lithium hydride-lithium liq. ammonia frans-Ethylene from acetylene derivatives with retention of hydroxyl groups... 

Alkylalkali compounds readily eliminate metal hydride to give the alkene this reaction is especially pronounced with the higher alkali metals. The microscopic reverse process has been modeled by the addition of LiH to ethylene. As shown in Figure 6, the reaction first involves a r-complex between ethylene and lithium hydride in which the structures of ethylene and of LiH are changed but little from the separated reactants. In the cyclic transition structure the C-Li bond has significantly shortened towards its value in the product ethyllithium. The C-H bond is still quite long in the transition structure but is on its way to a normal C-H bond. The same type of... 

The reaction of the dimers of lithium hydride or of methyllithium with the carbonyl group involves the same general principles. The only difference is that the additional molecule stays coordinated to the directly involved lithium throughout the reaction." A different situation exists for the reaction of methyllithium with ethylene oxide to give lithium propoxide (equation 6). 

CgH BiBr2, and diphenylbromobismuthine [39248-62-9] C22H2QBiBr, respectively, with lithium aluminum hydride or sodium borohydride at low temperatures yielded only black polymeric substances of empirical formula C H Bi (33). It has been claimed (34) that dimethylbismuthine and diphenylbismuthine can be used as cocatalysts for the polymerisation of ethylene (qv), propylene (qv), and 1,3-butadiene. The source of these bismuthines, however, was not mentioned. 

Tetrahydrofuran may be purified by refluxing over solid potassium hydroxide, followed by distillation from lithium alu-miniun hydride. Tetrahydrofuran may be replaced by ethylene glycol dimethyl ether (dimethoxyethane). The submitter has indicated that either solvent may be freed conveniently from water, alcohols, and moderate amounts of peroxides by passing the commercial solvent through a column (2 in. diameter X 2-3 ft. length) of Linde Air Products Molecular Sieves (type 13A iQ- n. pellets), at a rate of approximately 100 ml. per minute. 

The synthesis of 1,10-diaza-l 8-crown-6 (9) has been an important problem because this is the key starting material in the synthesis of numerous cryptands (see Chap. 8). Although first synthesized some years ago, the process has recently been patented. Di-azacrown 9 is prepared by a high dilution condensation of 1,8-diamino-3,7-dioxaoctane with ethylene glycol diacetyl chloride. The resulting diamide is then reduced with lithium aluminum hydride to give 9 in 56% overall yield from the open-chained diamine. The synthesis is illustrated In Eq. (4.8), below. 

Some instances of incomplete debromination of 5,6-dibromo compounds may be due to the presence of 5j5,6a-isomer of wrong stereochemistry for anti-coplanar elimination. The higher temperature afforded by replacing acetone with refluxing cyclohexanone has proved advantageous in some cases. There is evidence that both the zinc and lithium aluminum hydride reductions of vicinal dihalides also proceed faster with diaxial isomers (ref. 266, cf. ref. 215, p. 136, ref. 265). The chromous reduction of vicinal dihalides appears to involve free radical intermediates produced by one electron transfer, and is not stereospecific but favors tra 5-elimination in the case of vic-di-bromides. Chromous ion complexed with ethylene diamine is more reactive than the uncomplexed ion in reduction of -substituted halides and epoxides to olefins. ... 

An ethynylation reagent obtained by decomposition of lithium aluminum hydride in ethers saturated with acetylene gives a satisfactory yield of (64), Best results are obtained with the lithium acetylide-ethylene diamine complex in dioxane-ethylenediamine-dimethylacetamide. Ethynylation of (63) with lithium acetylide in pure ethylenediamine gives (64) in 95% yield. 

Acylation of norephedrine (56) with the acid chloride from benzoylglycolic acid leads to the amide (57), Reduction with lithium aluminum hydride serves both to reduce the amide to the amine and to remove the protecting group by reduction (58), Cyclization by means of sulfuric acid (probably via the benzylic carbonium ion) affords phenmetrazine (59), In a related process, alkylation of ephedrine itself (60) with ethylene oxide gives the diol, 61, (The secondary nature of the amine in 60 eliminates the complication of dialkylation and thus the need to go through the amide.) Cyclization as above affords phendimetra-zine (62), - Both these agents show activity related to the parent acyclic molecule that is, the agents are CNS stimulants... 

Preparation of 11 -Hydroxy-6a-Methylprogesterone A mixture of 2.68 g of 11-keto-6(3-methylprogesterone 3,20-bis-(ethylene ketal), 161 ml of tetrahydrofuran (previously distilled from lithium aluminum hydride), 1.34 g of lithium aluminum hydride and 14.5 ml of absolute ether was stirred and refluxed under nitrogen for 1.5 hours, then 27 ml of water was added cautiously, to decompose excess hydride. The resulting mixture was filtered and the filter cake was washed with 135 ml of ether. The combined filtrate and wash was shaken with 135 ml of water and separated. The aqueous layer was washed with four 55-ml portions of ether, then the organic layer and the washes were combined, washed once with water, and evaporated to dryness under diminished pressure leaving a tan residue. 

Cyclohexyloxyethanol has also been prepared by reduction of cyclohexyloxyacetic acid with lithium aluminum hydride 8 and by decomposition of cyclohexanone methanesulfonylhydrazone with sodium in ethylene glycol.9... 

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