Lithium compounds amides

SAFETY PROFILE A powerful irritant to skin, eyes, and mucous membranes. Flammable when exposed to heat or flame. Ammonia is liberated and Uthium hydroxide is formed when this compound is exposed to moisture. Reacts violently with water or steam to produce toxic and flammable vapors. Vigorous reaction with oxidizing materials. Exothermic reaction with acid or acid fumes. When heated to decomposition it emits very toxic fumes of LiO, NH3, and NOx. Used in synthesis of drugs, vitamins, steroids, and other organics. See also LITHIUM COMPOUNDS, AMIDES, AMMONIA, and LITHIUM HYDROXIDE. 

When the enamine is in conjugation with a carbonyl function, as in a-aminomethylene aldehydes (528,529), ketones (530), or esters (531), a Michael addition is found in vinylogous analogy to the reactions of amides. An application to syntheses in the vitamin A series employed a vinyl lithium compound (532). 

In the carbonylation reactions, further reaction of the acyl lithium compounds with carbon monoxide can occur, but clean reaction can be achieved if the lithium amide is first converted to a copper derivative (Scheme 130) (79JOC3734). In the case of morpholine, reaction with allyl bromide gave a 93% overall yield of the amide product. 

Deprotonation of a dihydrothiazine ring, followed by a reaction with an electrophile, is most straightforward in benzothiazin-3-ones (general structure 35), which are deprotonated at the 2-position by lithium diisopropyl amide (LDA). The enolate can then react with a variety of electrophiles including deuterium oxide, methyl iodide, and aldehydes <1982T3059>. Compound 70 was prepared in this manner from 2,4-dimethyldihydro-l,4-benzothiazin-3-one (Equation 27) <1985T569>. 

Homologues of ethoxyacetylene can be obtained by reaction of the metallated ethynyl ether in liquid ammonia with primary alkyl bromides and iodides 167]. Because of their better solubiliiy, the lithium compounds are preferred over their sodium and potassium analogues, lithium ethoxyacetylide is generated from the readily accessible 2-bromovinyl ethyl ether and two equivalents of lithium amide. This starting compound is obtained as a mixture of the E-and Z-isomer. When this mixture is heated with powdered KOH, only the Z-isomer is converted into ethoxyethyne. Alkali amides are able to conven both isomers into ethoxyethyne and its alkali compounds. A possible explanation for this violation of the "rule of... 

Lithium diethylamide has been shown to be an effective initiator for the homopolymerization of dienes and styrene llr2). It is also known that such a polymerization process is markedly affected by the presence of polar compounds, such as ethers and amines (2,3). However, there has been no report of the use of a lithium amide containing a built-in polar modifier as a diene polymerization initiator. This paper describes the preparation and use of such an initiator, lithium morpholinide. A comparison between polymerization with this initiator and lithium diethyl amide, with and without polar modifiers, is included. Furthermore, we have examined the effects of lithium-nitrogen initiators on the copolymerization of butadiene and styrene. 

A very large number of mixed metal aluminium amides has been reported. The majority are lithium-aluminium amide salts that exhibit a variety of different structures. Only a small number of ese compounds are discussed here.39,52,57,72,118-138 simplest is LiAl-(NH2)4 produced from the reaction of lithium and aluminium in liquid ammonia at 80 to 100 °C. The atomic arrangement of LiAl(NH2)4 has been studied by IR-spectroscopy and single crystal X-ray crystallography and was found to be a new variant of the GaPS4-type structure. 

Organonitrogen-lithium compounds, and particularly lithium amides (R2NLi), are widely used both in organic and in organometallic syntheses. For the former, these strong bases are employed as proton abstractors (5-8), to generate new organolithiums. These can then be derivatized with so-called electrophiles, e.g., alkyl and acyl halides (E+ = R+ and R—C+=0) and trimethylsilylchloride (E+ = MeaSi+) [Eq. (1)]. 

The unique feature of the alkyllithium compounds that makes them useful as diene initiators is their character as exceedingly powerful bases yet they are soluble in organic solvents and quite thermally stable. Alkyllithium compounds are sufficiently basic to add to hydrocarbon monomers. However, lithium salts of stabilized anions, such as acetylide and fluorenyl anions, are too weakly basic to add to such double bonds. Similarly, alkoxides and mercaptides fail to react with hydrocarbon monomers, but lithium alkyl amides react analogously to alkyllithium compounds. 

Table 13.4 allows for a comparison of the basicities of the strongest lithium-containing bases. The basicities are measured by the heats of deprotonation liberated upon mixing the reference acid isopropanol with these bases. These heats of deprotonation reveal that organo-lithium compounds are even stronger bases than lithium amides. Their basicities decrease from te/7-BuLi via. sec-BuLi and w-BuLi to PhLi. 

When 2,2-difluoro-3,3-dimethyl-1 -phenylsulfonylmethylcyclopropane is treated with lithium diisopropyl amide (LDA) or potassium hydroxide, a compound of empirical formula C12H13FO 2S is obtained. What is its structure, and how is it formed ... 

As most organometallic compounds, lithium enolates are highly polar entities susceptible to combine in various types of (eventually solvated) aggregates that undergo dynamic equilibria in solution. This phenomenon explains why enolate solutions are difficult to describe by the classical spectroscopic, physicochemical or theoretical methods, a difficulty enhanced by the sensitivity of these equilibria to many physicochemical factors such as the concentration, the temperature or the presence of complexing additives (lithium halides, amides, amines, HMPA,. ..). The problems due to dynamics are avoided in the solid state where many clusters of lithium enolates, alone or co-crystallized with exogenous partners, have been identified by X-ray crystallography. 

In the reaction of the lithium salt of 62 with acetone after a short lithiation time of 30 min, a 10% or 25% E Z mixture of 63 was obtained together with the addition product 64 in 65% yield (equation 42)65. The formation of only one addition product, and the quick disappearance of the -isomer, are due to a fast deprotonation process the -isomer compared with the Z-isomer, and the high rate of equilibration between the lithium compounds that greatly favors the syn anion, which reacts with acetone to give 64. These results point out that the formation of the syn lithium compounds is favored in oxime ethers for kinetic as well as for thermodynamic reasons. The kinetic preference, according to Ensley and Lohr65, is due to coordination between the lithium amide and the oxime oxygen. 

Conversion of phosphonium salts to salt-free solutions of ylides can also be effected with sodium bis(trimethylsilyl)amide. As it is soluble in many solvents, and easy to handle and to weigh out, sodium bis(trimethylsilyl)amide is preferred to sodamide in liquid ammonia in many cases (equation 11). The corresponding potassium and lithium compounds can also be used. ... 

With some very strong bases, such as alkyl-sodium or -lithium compounds or sodium amide, ethers can be converted to alkenes (Scheme 23). The reaction is supported by electron-withdrawing groups in the p-position thus, Et0CH2CH(C02R)2 can be converted to H2C==C(C02R)2 (retro-Michael-type reaction). 

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