Amides alane

Although hydrogenation of the 2 1 alanate-amide dehydrogenation products was not attempted, there is no reason to believe this reaction will not also stop at the formation of LiH and LiNH2 like those for the 1 1 and 1 2 ratios. 

Niobium, tris(diethyldilhiocarbamato)oxy-stereochemistry, 1,82 structure, 1, 83 Niobium, tris(oxa ato)oxy-stereochcmistry, 1, 82 Niobium, tris(phcnylcncdirhio)-structure, 1, 63 Niobium alanate, 3, 685 Niobium complexes alkyl alkoxy reactions, 2, 358 amides, 2,164 properties, 2, 168 synthesis, 2, 165 applications, 6,1014 carbamicacid, 2, 450 clusters, 3, 672,673,675 hexamethylbenzene ligands, 3, 669 cyanides synthesis, 2, 9 p-dinitrogen, 3, 418 fluoro... 

Alane is also a useful group for reducing amides and it, too, can be used to reduce amides to amines in the presence of ester groups. 

The electrophilicity of alane is the basis for its selective reaction with the amide group. Alane is also useful for reducing azetidinones to azetidines. Most nucleophilic hydride reducing agents lead to ring-opened products. DiBAlH, A1H2C1, and A1HC12 can also reduce azetinones to azetidines.100... 

The reason why the carbonyl group in -santonin remained intact may be that, after the reduction of the less hindered double bond, the ketone was enolized by lithium amide and was thus protected from further reduction. Indeed, treatment of ethyl l-methyl-2-cyclopentanone-l-carboxylate with lithium diisopropylamide in tetrahydrofuran at — 78° enolized the ketone and prevented its reduction with lithium aluminum hydride and with diisobutyl-alane (DIBAL ). Reduction by these two reagents in tetrahydrofuran at — 78° to —40° or —78° to —20°, respectively, afforded keto alcohols from several keto esters in 46-95% yields. Ketones whose enols are unstable failed to give keto alcohols [1092]. 

High yields of amines have also been obtained by reduction of amides with an excess of magnesium aluminum hydride (yield 100%) [577], with lithium trimethoxyaluminohydride at 25° (yield 83%) [94] with sodium bis(2-methoxy-ethoxy)aluminum hydride at 80° (yield 84.5%) [544], with alane in tetra-hydrofuran at 0-25° (isolated yields 46-93%) [994, 1117], with sodium boro-hydride and triethoxyoxonium fluoroborates at room temperature (yields 81-94%) [1121], with sodium borohydride in the presence of acetic or trifluoroacetic acid on refluxing (yields 20-92.5%) [1118], with borane in tetrahydrofuran on refluxing (isolated yields 79-84%) [1119], with borane-dimethyl sulflde complex (5 mol) in tetrahydrofuran on refluxing (isolated yields 37-89%) [1064], and by electrolysis in dilute sulfuric acid at 5° using a lead cathode (yields 63-76%) [1120]. 

Amides containing nitro groups are reduced to diamino compounds with alane. A, A -Dimethyl-p-nitrobenzamide, on reduction with lithium aluminum hydride in the presence of sulfuric acid in tetrahydrofuran, gave 98% yield of dimethyl-p-aminobenzylamine [1117]. 

There are several reports of methods that will selectively reduce a tertiary amide in the presence of a secondary amide[59]. The secondary lactam of 101 was protected as the lactim ether 107 and treated with diborane however, the spectral characteristics of the major products isolated were consistent with reduction of both the tertiary amide and the lactim ether. In 1991 Martin et al. [60] successfully used alane to reduce a tertiary amide in the presence of an oxindole (secondary amide) relying on the known rate difference for reduction between these two groups [61]. 

However, initial experiments with this reagent gave poor results, with the secondary amide undergoing reduction along with the tertiary amide. Compound 101 [and 107, Fig. (29)] is sufficiently twisted such that the gem-dimethyl groups effectively block the (j-face of the tertiary amide, leaving the a-face relatively unencumbered. However, a modification of the alane procedure [60], proved satisfactory for this transformation. The piperazinedione 101 was pretreated with AlEt3, with the expectation that this Lewis acid would form a complex with the more exposed secondary lactam [106, Fig.(29).] and leave the tertiary lactam accessible for reduction. 

Most stable solids in this category of materials are generally metal amides containing the NH2 radical. With a lower hydrogen stoichiometry than the alanates or borohydrides, their overall capacities are somewhat lower. However, they readily form with lightweight elements and are generally reacted with other hydrides. Thus, they have the potential to contain comparable amounts of recoverable hydrogen. 

Other combinations of hydrides with amides have been considered. Nakamori et al 80 83 others have looked at mixtures of Li amide with Li alanate and with Li borohydride. DFT calculations suggest that these systems will behave in a fashion similar to that of the destabilized borohydrides described above that is, the reaction products in the dehydrogenated state should have lower enthalpies than the borohydride or the alanate alone. The potential yields are higher than with LiH. For the borohydride case, the expected reaction pathway is... 

The discussion above was limited to alanates, borohydrides, amides, and combinations of these materials. Other hydrides or alternative approaches have also been proposed for storage applications. Zaluska et al. ° studied lightweight lithium-beryllium hydride and showed a reversible hydrogen capacity of over 8 wt%. They also showed that the hydride may be usable down to 150°C. Although these results are rather promising, it is unlikely that any beryllium-containing compound would be considered for vehicular use because of the toxicity of this element, even though the hydride may be quite stable. 

Within the past year, a few papers have been published describing MAS-NMR experiments to evaluate transitions between the amide/imide phases [18] and also for amide-alanate mixtures [16, 17, 26]. Nearly aU of these studies have used either the Li isotopes or A1 when the alanates were involved. As shown in Figure 4, the Li MAS and CPMAS specda are especially useful to discriminate... 

Alane (AIH3) and its derivatives have also been utilized in the reduction of carboxylic acids to primary alcohols. It rapidly reduces aldehydes, ketones, acid chlorides, lactones, esters, carboxylic acids and salts, tertiary amides, nitriles and epoxides. In contrast, nitro compounds and alkenes are slow to react. AIH3 is particularly useful for the chemoselective reduction of carboxylic acids containing halogen or nitro substituents, to produce the corresponding primary alcohols. DIBAL-H reduces aliphatic or aromatic carboxylic acids to produce either aldehydes (-75 °C) or primary alcohols (25 C) Aminoalu-minum hydrides are less reactive reagents and are superior for aldehyde synthesis. ... 

Complex alkenyl-copper and -cuprate derivatives, and also alanates, have been generated with high stereochemical purity, and upon treatment with iV-chloromethyl-iV-methylformamide or iV-chloromethyl-phthalimide provide access to highly functionalized allylic amides (entries 1 and 2, Table 7). Addition to acyliminomalonic esters or acyliminophosphonates provides acylaminomalonates and acylamino-alkylphosphonates in modest yield (entries 3 and 4, Table 7). 

Alkynoic esters, 493-494 Alkynyldiethyl alanes, 144 Allene cyclo-oligomerization, 41 Allenes, 161,315-316,438 Allenic adds, 149-150 Allenic amides, 255... 

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