Lithium aluminum hydride, reducing table

Section 20 9 Esters react with Gngnard reagents and are reduced by lithium aluminum hydride (Table 20 4)... 

Alkyl azides prepared by nucleophilic substitution of alkyl halides by sodium azide as shown m the first entry of Table 22 3 are reduced to alkylammes by a variety of reagents including lithium aluminum hydride... 

Lithium borohydride is a more powerful reducing agent than sodium borohydride, but not as powerful as lithium aluminum hydride (Table 6). In contrast to sodium borohydride, the lithium salt, ia general, reduces esters to the corresponding primary alcohol ia refluxing ethers. An equimolar mixture of sodium or potassium borohydride and a lithium haUde can also be used for this purpose (21,22). 

Aldehydes and ketones have also been prepared by nucleophilic cleavage of resin-bound O-alkyl hydroxamic acids (Weinreb amides [744]) with lithium aluminum hydride [745] or Grignard reagents (Entries 1 and 2, Table 3.41). Similarly, support-bound thiol esters can be cleaved with Grignard reagents to yield ketones [272], or with reducing agents to yield aldehydes (Entry 3, Table 3.41). Polystyrene-bound sele-nol esters (RCO-Se-Pol) react with alkynyl cuprates to yield alkynyl ketones [746]. 

Polystyrene-bound carboxylic esters have been reduced with diisobutylaluminum hydride or lithium aluminum hydride. Use of the latter reagent can, however, lead to the formation of insoluble precipitates, which could readily cause problems if reactions are performed in fritted reactors. An alternative procedure for reducing carboxylic esters to alcohols involves saponification, followed by activation (e.g. as the mixed anhydride) and reduction with sodium borohydride (Entries 10 and 11, Table... 

Carbamates can be reduced by lithium aluminum hydride (Entry 3, Table 3.22 [179]) or by Red-Al (Entry 5, Table 10.11). Illustrative examples of the reduction of amides and carbamates on solid phase are listed in Table 10.11. 

Other reagents that have been used to reduce support-bound aromatic nitro compounds include phenylhydrazine at high temperatures (Entry 5, Table 10.12), sodium borohydride in the presence of copper(II) acetylacetonate [100], chromium(II) chloride [196], Mn(0)/TMSCl/CrCl2 [197], lithium aluminum hydride (Entry 3, Table... 

Substituted cyclohexanols containing a 1-perfluorophenyl substituent are surprisingly, when compared with 1-alkylpentafluorobenzenes (vide supra), reduced at the ortho C F bond in the aromatic ring by lithium aluminum hydride.87 Substituted phenols with a trifluoromethyl group in the ortho or para positions are reduced with lithium aluminum hydride66 (Table 3), in contrast to 3-(trifluoromethyl)phenol. 

Different hydrogenolytic reactivity of trifluoromethyl groups with respect to their position on the quinoline ring is observed. All C-F bonds in 2-, 4- and 6-(trifluoromethyl)quinoline are hydrogenolyzed by lithium aluminum hydride (Table 4), but the 3-trifluoromethyl isomer gave 3-(difluoromethyl)-l,2-dihydroquinoline (10) under the same experimental conditions in contrast to these results, sodium borohydride surprisingly reduces 3-(trifluoromethyl)quinoline to the corresponding 3-methylquinoline (Table 4).149... 

Metal hydrides, such as lithium aluminum hydride, also can be used to reduce derivatives of carboxylic acids (such as amides and nitriles see Table 16-6) to aldehydes. An example follows ... 

Several purine esters have been prepared, especially 6- and 8-derivatives. They readily aminate to amides and may be reduced with lithium aluminum hydride to the corresponding alcohols. Table 30 lists several reactions of typical esters. 

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