Lithium aluminum hydride, reaction

Lithium aluminum hydride, reaction with aldehydes, 610 reaction with carboxylic acids. 611-612... 

Oxymercuration of simple alkyl- and acyl-substituted cyclopropenes generally results in ring opening.Addition of mercury(II) acetate to 3-methyl-3-phenylcyclopropene, however, gave a low yield of a cyclopropane containing organomercury compound (15-20%), which was converted into an isomeric mixture of 1 -methoxy-2-methyl-2-phenylcyclopropanes by reduction with lithium aluminum hydride. Reaction of 5 with mercury trifluoroacetate in methanol and then sodium hydroxide led predominantly to one cylopropane. ... 

Synthesis by high-dilution techniques requires slow admixture of reagents ( 8-24 hrs) or very large volumes of solvents 100 1/mmol). Fast reactions can also be carried out in suitable flow cells (J.L. Dye, 1973). High dilution conditions have been used in the dilactam formation from l,8-diamino-3,6-dioxaoctane and 3,6-dioxaoctanedioyl dichloride in benzene. The amide groups were reduced with lithium aluminum hydride, and a second cyclization with the same dichloride was then carried out. The new bicyclic compound was reduced with diborane. This ligand envelops metal ions completely and is therefore called a cryptand (B. Dietrich, 1969). 

Carboxylic acids are exceedingly difficult to reduce Acetic acid for example is often used as a solvent in catalytic hydrogenations because it is inert under the reaction con ditions A very powerful reducing agent is required to convert a carboxylic acid to a pri mary alcohol Lithium aluminum hydride is that reducing agent... 

In contrast to alcohols with their nch chemical reactivity ethers (compounds contain mg a C—O—C unit) undergo relatively few chemical reactions As you saw when we discussed Grignard reagents m Chapter 14 and lithium aluminum hydride reduc tions m Chapter 15 this lack of reactivity of ethers makes them valuable as solvents m a number of synthetically important transformations In the present chapter you will learn of the conditions m which an ether linkage acts as a functional group as well as the methods by which ethers are prepared... 

The reaction of esters with Gngnard reagents and with lithium aluminum hydride both useful m the synthesis of alcohols were described earlier They are reviewed m Table 20 4 on page 848... 

Reactions. Although lithium aluminum hydride is best known as a nucleophilic reagent for organic reductions, it converts many metal haUdes to the corresponding hydride, eg, Ge, As, Sn, Sb, and Si (45). 

Hydroisoquinolines. In addition to the ring-closure reactions previously cited, a variety of reduction methods are available for the synthesis of these important ring systems. Lithium aluminum hydride or sodium in Hquid ammonia convert isoquinoline to 1,2-dihydroisoquinoline (175). Further reduction of this intermediate or reduction of isoquinoline with tin and hydrochloric acid, sodium and alcohol, or catalyticaHy using platinum produces... 

The reductions of chlorosilanes by lithium aluminum hydride, lithium hydride, and other metal hydrides, MH, offers the advantages of higher yield and purity as well as dexibiUty in producing a range of siUcon hydrides comparable to the range of siUcon haUdes (59). The general reaction is as follows ... 

Good yields of phenylarsine [822-65-17, C H As, have been obtained by the reaction of phenylarsenic tetrachloride [29181-03-17, C H AsCl, or phenyldichloroarsine [696-28-6], C3H3ASCI25 with lithium aluminum hydride or lithium borohydride (41). Electrolytic reduction has also been used to convert arsonic acids to primary arsines (42). Another method for preparing primary arsines involves the reaction of arsine with calcium and subsequent addition of an alkyl haUde. Thus methylarsine [593-52-2], CH As, is obtained in 80% yield (43) ... 

Reduction. Coumarin is reduced to o-hydroxycinnamyl alcohol by reaction with lithium aluminum hydride (21). By reaction with diborane coumarin gives o-aUylphenol [1745-81 -9] (22). 

An 80% yield of tetraphenylfuran is obtained by treatment of benzoyl chloride with active titanium generated by lithium aluminum hydride reduction of titanium trichloride (Scheme 84e) (8UOC2407). The reaction nroceeds via benzil and tetraphenylbut-2-ene-l,4-dione, both of which are minor products of the reaction. 

In most other reactions the azolecarboxylic acids and their derivatives behave as expected (cf. Scheme 52) (37CB2309), although some acid chlorides can be obtained only as hydrochlorides. Thus imidazolecarboxylic acids show the normal reactions they can be converted into hydrazides, acid halides, amides and esters, and reduced by lithium aluminum hydride to alcohols (70AHC(12)103). Again, thiazole- and isothiazole-carboxylic acid derivatives show the normal range of reactions. 

Besides the salts (458) and (459) previously described, aminopyrazolium salts can be obtained from the reaction between amines and chloropyrazolium salts (Section 4.04.2.3.7(ii)) or by quaternization of iminopyrazplines as in (461)—> (462) (72BSF2807). The lithium aluminum hydride reduction of the salt (462) affords mixtures of reduced and open-chain pyrazoles (Figure 23 Section 4.04.2.1.6(i)). 

Lithium aluminum hydride reduction of 2,3,4-triphenylisoxazolin-5-one yielded 1,2,3-triphenylaziridine and dibenzylaniline. The reaction was considered to proceed by a concerted [l,3]-sigmatropic migration of the N to a C atom. HOMO-LUMO calculations show this type of concerted reaction is possible (Scheme 68) (80JA1372). 

Reductive cleavage of oxiranes to alcohols by lithium aluminum hydride is an important reaction (64HC(19-1)199), but the most powerful hydride donor for this purpose is lithium triethylborohydride (73JA8486). 

Treatment of thiiranes with lithium aluminum hydride gives a thiolate ion formed by attack of hydride ion on the least hindered carbon atoms (76RCR25), The mechanism is 5n2, inversion occurring at the site of attack. Polymerization initiated by the thiolate ion is a side reaction and may even be the predominant reaction, e.g. with 2-phenoxymethylthiirane. Use of THF instead of ether as solvent is said to favor polymerization. Tetrahydroborates do not reduce the thiirane ring under mild conditions and can be used to reduce other functional groups in the presence of the episulfide. Sodium in ammonia reduces norbornene episulfide to the exo thiol. 

An aiyl methane- or toluenesulfonate ester is stable to reduction with lithium aluminum hydride, to the acidic conditions used for nitration of an aromatic ring (HNO3/HOAC), and to the high temperatures (200-250°) of an Ullman reaction. Aiyl sulfonate esters, formed by reaction of a phenol with a sulfonyl chloride in pyridine or aqueous sodium hydroxide, are cleaved by warming in aqueous sodium hydroxide. ... 

The excess lithium aluminum hydride and the metallic complexes are decomposed by the careful addition of 82 ml. of distilled water, from a dropping funnel, to the well-stirred mixture. The reaction mixture is stirred for an additional 30 minutes, filtered with suction, and the solid is washed with several 100-ml. portions of ether. After the ether is removed from the filtrates, the residual oil is distilled under reduced pressure. The yield of laurylmethylamine, a colorless liquid boiling at 110-115°/1.2-1.5 mm., is 121-142 g. (81-95%) (Note 6). 

Ethoxy-2-cyclohexenone is a useful intermediate in the synthesis of certain cyclohexenones. The reduction of 3-ethoxy-2-cyclohexenone with lithium aluminum hydride followed by hydrolysis and dehydration of the reduction product yields 2-cyclo-hexenone. Similarly, the reaction of 3-ethoxy-2-cyclohexenone with Grignard reagents followed by hydrolysis and dehydration of the addition product affords a variety of 3-substituted 2-cyclo-hexenones. ... 

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