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Lithium tri-t-butoxyaluminum hydride

A cold (0°) solution of 15 g (0.039 mole) of cholest-4-en-3-one, mp 79-80°, in 200 ml of ether-benzene (8 1) is added dropwise to 0.05 mole of lithium tri-t-butoxyaluminum hydride in ether-diglyme at —40° to —50°. The mixture is allowed to stand overnight at 0° and then hydrolyzed by treatment with ice, 5 N sodium hydroxide and Rochelle salt. Evaporation of the washed and dried ether extracts and crystallization of the residue from ethyl acetate affords 13 g (87 % yield) of nearly pure cholest-4-en-3j9-ol, mp 126-129°. One recrystallization from the same solvent gives the pure product as large needles mp 131-132°, [a]o 46° reported mp 132° [a]c, 44° (benzene). [Pg.99]

The introduction of the l/, 2j5-methylene function into cortical hormones is best carried out by starting with the A -3)S-aIcohols (7) which are prepared by lithium aluminum hydride or lithium tri-t-butoxyaluminum hydride reduction of the corresponding A -3-ketones. [Pg.109]

Because 3-substituted 1,2-amino alcohols and even P-alkyl-y-hydroxy-5-amino esters are potentially precursors to pharmacologically interesting materials, further investigations have been carried out to extend the methodology in this direction. Thus, the reduction of the ketone moiety of 56 by applying L-selectride or lithium tri-t-butoxyaluminum hydride opened access to the cis-amino lactones 58 (45-54% yield de = 90-94%) and the trans-amino lactones 58 (67-76% yield de > 98%), respectively (Scheme 1.1.16). Monodebenzylation with cerium ammoni-... [Pg.15]

Acid chlorides, R(Ar)COCl, are reduced to R(Ar)CHO by Hj/Pd(S), a moderate catalyst that does not reduce RCHO to RCHjOH (Rosenmund reduction). Acid chlorides, esters (R(Ar)COOR), and nitriles (RC N) are reduced with lithium tri-t-butoxyaluminum hydride, LiAlH[OC(CH3)3]j, at very low temperatures, followed by HjO. The net reaction is a displacement of X by H",... [Pg.319]

Lithium tri-t-butoxyaluminum deuteride, 162 Lithium tri-t-butoxyaluminum hydride, 80, 84, 100... [Pg.262]

Acylthiazolidine-2-thiones (593), easily prepared from carboxylic acids and thiazolidine-2-thione, can be reduced to the corresponding aldehydes with diisobutyl-aluminum hydride in toluene at -78 to -40 °C in 70-90% yield or with lithium tri-t-butoxyaluminum hydride in THF at -20 to 0 °C in 80-90% yield (Scheme 130) (79BCJ555). The formation of the aluminum-containing six-membered chelate (594) in this reaction process is probable and is supported by the fact that no decrease in yield is observed on changing the mole ratio of DIBAL from 1.2 to 2.1 equivalents. [Pg.469]

Lithium tri-t-butoxyaluminum hydride readily reduces aldehydes and ketones to the corresponding alcohols and reduces acid chlorides to aldehydes. Epoxides, esters, carboxylic acids, tert-amides, and nitriles are not, or only slowly, reduced. Thus, the reagent may be used for chemoselective reductions. ... [Pg.105]

Reduction of N-(3-bromopropyl)isoquinolinium bromide (4) with lithium tri-t-butoxyaluminum hydride (1, 620-625 2, 251-252 3, 188) gives the 1,2-dihydroiso-quinoline (5), which on treatment with ethanolic methylamine yielded (6), the N-methyl analog of (3, n = 2). [Pg.150]

Lithium tri-t-butoxyaluminum hydride, LiAlH[OC(CHj)3]3. Mol. wt. 254.30, sublimes at 280° under vacuum, solubility at 25° in g./lOO g. diglyme, 41 tetrahydrofurane 36, ether, 2 1,2-dimethoxyethane, 4 t-BuOH, 0. Supplier Ventron Corp. The reagent currently costs 1.5 as much as LiAlH and the active hydrogen per gram is only 3.7% that for LiAlHa. [Pg.313]

One of the more difficult selective reductions to accomplish is the conversion of a carboxylic acid derivative to an aldehyde without overreduction to the alcohol. Several approaches have been used to achieve this selectivity. One is to replace some of the hydrides by bulky groups, thus modifying reactivity by steric factors. Lithium tri-t-butoxyaluminum hydride is an example of this approach. This reagent is prepared by addition of an appropriate quantity of t-butanol to LiAlFL. As noted in... [Pg.131]

Table 4.1, lithium tri-t-butoxyaluminum hydride can be used to reduce acid chlorides to the aldehyde stage without extensive overreduction to the alcohol. Other trialkoxyaluminum hydrides prepared from less bulky primary alcohols have been prepared and their reactivity studied. In many instances, they show selectivity superior to that of the simple hydrides. [Pg.132]


See other pages where Lithium tri-t-butoxyaluminum hydride is mentioned: [Pg.149]    [Pg.655]    [Pg.51]    [Pg.268]    [Pg.197]    [Pg.156]    [Pg.286]    [Pg.586]    [Pg.261]    [Pg.263]    [Pg.265]    [Pg.160]    [Pg.631]    [Pg.314]    [Pg.314]    [Pg.384]    [Pg.97]    [Pg.243]    [Pg.235]    [Pg.276]   
See also in sourсe #XX -- [ Pg.15 ]

See also in sourсe #XX -- [ Pg.292 , Pg.312 , Pg.399 ]




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