Lithium with aluminum

Metallurgy. Lithium forms alloys with numerous metals. Early uses of lithium alloys were made in Germany with the production of the lead alloy, BahnmetaH (0.04% Li), which was used for bearings for railroad cars, and the aluminum alloy, Scleron. In the United States, the aluminum alloy X-2020 (4.5% Cu, 1.1% Li, 0.5% Mn, 0.2% Cd, balance Al) was introduced in 1957 for stmctural components of naval aircraft. The lower density and stmctural strength enhancement of aluminum lithium alloys compared to normal aluminum alloys make it attractive for uses in airframes. A distinct lithium—aluminum phase (Al Li) forms in the alloy which bonds tightly to the host aluminum matrix to yield about a 10% increase in the modules of elasticity of the aluminum lithium alloys produced by the main aluminum producers. The density of the alloys is about 10% less than that of other stmctural aluminum alloys. 

The extent of olefin formation depends on the position of the functional group, " on the degree of a-substitution and on the concentration of the hydride (or deuteride). Usually olefin formation can be largely suppressed by increasing the concentration of lithium aluminum deuteride. With certain tosylhydrazones, however, such as the C-17 derivative (103), olefin (104) is a major product irrespective of the quantity of the reagent used. ... 

Reduction of l-methyl-2-alkyl-.d -pyrroline and l-methyl-2-alkyl-.d -piperideine perchlorates with complex hydrides prepared in situ by partial decomposition of lithium aluminum hydride with the optically active alcohols (—)-menthol and (—)-borneol affords partially optically active l-methyl-2-alkyl pyrrolidines (153, n = 1) and 1-methy 1-2-alkyl piperideines (153, n = 2), respectively (241,242). 

The reaction of lithium aluminum hydride with l//-l,4-benzodiazepine-2,5(3//,4//)-dione (3) gives 2,3,4,5-tetrahydro-l//-l,4-benzodiazepinc (12).209... 

The concentration of this solution was established by decomposing the lithium aluminum hydride with excess iodine according to the following equation ... 

Shibasaki showed that an aluminum-lithium-BINOL complex (ALB) also catalyzes the asymmetric addition of dialkyl phosphites to aldehydes, with ees ranging from 55 to 90% for aryl or unsaturated aldehydes (Scheme 5-37). 

Olsen, L., and R. T. Sanderson The Reaction of Aluminum Chloride with Lithium Borohydride. J. Inorg. Nucl. Chem. 7, 228 (1958). 

R)-aluminum-lithium-BINOL complex (0.024 g, 0.04 mmol) was dissolved in toluene (0.4 ml), and to this solution was added dimethyl phosphite (0.044 g, 0.4 mmol) at room temperature the mixture was stirred for 30 min. Benzaldehyde (0.042 g, 0.4 mmol) was then added at -40°C. After having been stirred for 51 h at -40°C, the reaction mixture was treated with 1 N hydrochloric acid (1.0 ml) and extracted with ethyl acetate (3 x 10 ml). The combined organic extracts were washed with brine, dried over sodium sulfate, and concentrated under reduced pressure. The residue was purified by flash chromatography (silica, 20% acetone/hexane) to give the diethyl (S)-a-hydroxybenzylphosphonate (78 mg, 90%) with 85% enantiomeric excess as a colorless solid of mp 86 to 87°C. 

Lithium aluminum hydride, with aluminum chloride, for reduction of 4-f-butylcydohexanone, 47,17 in reduction of 1,4-dioxaspiro[4.5J-decane, 47, 38... 

Moreover, these rare earth heterobimetallic complexes can be utilized for a variety of efficient catalytic asymmetric reactions as shown in Scheme 7 Next we began with the development of an amphoteric asymmetric catalyst assembled from aluminum and an alkali metal.1171 The new asymmetric catalyst could be prepared efficiently from LiAlH4 and 2 mol equiv of (R)-BINOL, and the structure was unequivocally determined by X-ray crystallographic analysis (Scheme 8). This aluminum-lithium-BINOL complex (ALB) was highly effective in the Michael reaction of cyclohexenone 75 with dibenzyl malonate 77, giving 82 with 99% ee and 88 % yield at room temperature. Although LLB and... 

Reduction of a-methyl-fi-hydroxy ketones,2 The r-butyldimethylsilyl ethers of these ketones, in which chelation is difficult, are reduced by lithium aluminum hydride with a high degree of 1,2-anri-selectivity. This reaction can therefore afford either aM ,a/iri-l,3-diols or anti,syn- 1,3-diols with high selectivity. 

The modification of lithium aluminum hydride with chiral auxiliary reagents has resulted in several highly effective reagents, particularly for the reduction of aryl alkyl ketones and a,0-acetylenic ketones. Applications of several of these reagents to key reduction steps in more complex syntheses have been highly successful. Chiral tricoordinate aluminum reagents have given lower enantiomeric excesses of alcohols. 

E.C. Ashby, R.D. Schwartz, B.D. James, Concerning the preparation of magnesium aluminum hydride. A study of the reactions of lithium and sodium aluminum hydrides with magnesium halides in ether solvents , Inorg. Chem. 9 (1970) 325-332. 

Contact of lithium aluminum hydride with water may cause fire or explosion. 

From the equation showing the mechanism it is evident that 1 mol of lithium aluminum hydride can reduce as many as four molecules of a carbonyl compound, aldehyde or ketone. The stoichiometric equivalent of lithium aluminum hydride is therefore one fourth of its molecule, i.e. 9.5 g/mol, as much as 2 g or 22.4 liters of hydrogen. Decomposition of 1 mol of lithium aluminum hydride with water generates four molecules of hydrogen, four hydrogens from the hydride and four from water. 

Opening of a bottle where some particles of lithium aluminum hydride were squeezed between the neck and the stopper caused a fire [68]. Lithium aluminum hydride must not be crushed in a porcelain mortar with a pestle. Fire and even explosion may result from contact of lithium aluminum hydride with small amounts of water or moisture. Sodium bis(2-methoxy-ethoxy)aluminum hydride (Vitride, Red-Al ) delivered in benzene or toluene solutions also may ignite in contact with water. Borane (diborane) ignites in contact with air and is therefore kept in solutions in tetrahydrofuran or in complexes with amines and sulfides. Powdered lithium borohydride may ignite in moist air. Sodium borohydride and sodium cyanoborohydride, on the other hand, are considered safe. ... 

Reaction of the products of reduction with lithium aluminum hydride with water is very exothermic. This is especially true of reductions in which an excess of lithium aluminum hydride has been used. In such cases it is advisable to decompose the unreacted hydride by addition of ethyl acetate (provided its reduction product - ethanol - does not interfere with the isolation of the products). Then normal decomposition with water is carried out followed by acids [5i] or bases [121]. 

Lithium aluminum hydride reduces preferentially the carbonyl function (p. 98) but alanes prepared by reactions of aluminum hydride with two equivalents of isopropyl or /er/-butyl alcohol or of diisopropylamine reduce the conjugated double bonds with high regioselectivity in quantitative yields [871] (p. 121). 

Heteroaromatics are subdivided, according to the electron influence of the heteroatom, into w-electron-deficient compounds and compounds with an excess of it electrons on the ring carbon atoms. The typical ff-electron-delicient compound pyridine has so far been made to react only in one case the reaction of lithium tetrakis(A-dihydropyridyl)-aluminate (LDPA) [112-114), obtainable from pyridine and lithium aluminum hydride, with trifluoromethanesulfenyl chloride in an excess of pyridine affords 3-trifluoromethylmercaptopyridine in low yield (13%) (60). This reaction probably occurs through sulfenylation of the l,2-dihydrop5T idyl moiety of the LDPA with the formation of a 2,5-... 

Another type of adducts [8, Eq. (3)] was formed by the reaction of di(fert-butyl)aluminum chloride with dilithium bis(trimethylsilyl)hydrazide in low yields below 30% [19]. The structure of 8 consists of a distorted heterocubane with four vertices occupied by nitrogen atoms, two of which are connected by an intact N—N bond across one face of the cube. The cation positions are occupied by two aluminum and two lithium atoms, of which the last ones bridge the N—bond. Part of the hydrazide molecules was cleaved, and the aluminum atoms are bonded to one ferf-butyl group only. On the basis of the NMR spectroscopic characterization many unknown by-products were formed in the course of that reaction, and no information is available concerning the reaction mechanism. Compound 8 may be described as an adduct of dilithium bis(trimethylsilyl)hydrazide to a dimeric iminoalane containing a four-membered AI2N2 heterocycle. Further... 

As part of the structure proof iV-f- butyl-1,2-oxazetidine was treated with lithium aluminum hydride with cleavage at the O—N bond (Scheme 32) (7UA4082). 

The submitters used benzene distilled from lithium aluminum hydride, but the checkers used ACS-grade benzene as well as benzene distilled from lithium aluminum hydride, with no significant change in yield. 

Lithium r-butylUs(2-Diethylpropyl)aluminate, t.i[(/-C4H9) ,Al(/-C4H/>)H] (1). Mol. wt. 206.26. The lithium trialkylaluminate is prepared by reaction of diisobutyl-aluminum hydride with r-hutyllithium. Related hydrides can be prepared with n-butyllithium and. wc-butyllithium. 

The main methods of reducing ketones to alcohols are (a) use of complex metal hydrides (b) use of alkali metals in alcohols or liquid ammonia or amines 221 (c) catalytic hydrogenation 14,217 (d) Meerwein-Ponndorf reduction.169,249 The reduction of organic compounds by complex metal hydrides, first reported in 1947,174 is a widely used technique. This chapter reviews first the main metal hydride reagents, their reactivities towards various functional groups and the conditions under which they are used to reduce ketones. The reduction of ketones by hydrides is then discussed under the headings of mechanism and stereochemistry, reduction of unsaturated ketones, and stereochemistry and selectivity of reduction of steroidal ketones. Finally reductions with the mixed hydride reagent of lithium aluminum hydride and aluminum chloride, with diborane and with iridium complexes, are briefly described. 

In this context, a chiral hydride reagent, BINAL-H, prepared by modification of lithium aluminum hydride with equimolar amounts of optically pure binaphthol and a simple alcohol, is extremely useful (9b, 18a, 35) Scheme 15 shows the utility of the three-component coupling synthesis. The < > side-chain unit and the hydroxycyclopentenone can be prepared with very high enantioselectivity by reduction of the corresponding enone precursors (35-38). 

Henbest and co-worker 70 -702 used controlled amounts of lithium aluminum hydride -with success in the syntheda of steroid epoxides-Thue, 5j8t60-epoxides (Eq. 208), 90,110-epoxides (Eq. 207), and 110120 epoxide (Eq. 208) were obtainable by reduction of Ca-bromo-rt-os . Qa-bromo-U-uxo, and 12a-bromo-ll-oxo steroid precursors respec-... 

Perfluoroisoquinoline, resembling isoquinoline itself, is most susceptible to hydride nucleophilic attack at Cl l//-perfluoroisoquinoline (11) results as the sole product from the reaction of lithium aluminum hydride with perfluoroisoquinoline.150... 

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