Reducing agents lithium aluminium hydride

Being a versatile reducing agent, lithium aluminium hydride reduces both alkyl and aryl halides to hydrocarbons. 

Qinghaosu can be reduced even more with sodium borohydride in the presence of boron trifluoride to deoxoqinghaosu (100). ° 100 can also be obtained by reduction of 98 with BH3NEt3 and Me3SiCl in DME. ° The more powerful reducing agent lithium aluminium hydride reduces not only lactone and peroxy group, but also acetal and ketal, to yield the exhaustively reduced product 101 and partially reduced products (Scheme 5-3). ° °°... 

The reactions are commonly initiated with AIBN at ca. 80 °C in a solvent such as benzene or toluene, but alkyl halides have also been reduced at -60 °C with tributyltin hydride under sonication conditions.133-134 Some reductions of halides have been carried out by generating the tin hydride in situ from a molar equivalent of the reducing agent [lithium aluminium hydride, sodium borohydride, or poly(methylhydrosiloxane)] and a catalytic amount of organotin hydride, halide, or oxide. Reduction of halides has also been carried out under aqueous conditions, using 4,4 -azobis(4-cyanovaleric acid) (ACVA) as a water-soluble radical initiator.60... 

Elimination from vicinal dihalides has also been accomplished with the reducing agent, lithium aluminium hydride and the nucleophilic thiophenox-ide but mechanistic details other than anti stereospecificity are lacking. 

Carbonyl compounds can be reduced back to alcohols by using the reducing agents lithium aluminium hydride (LiAlH4) or sodium borohydride (NaBH4). 

Some of the functional groups which are reduced by lithium aluminium hydride, the reduction product together with the theoretical mols of reducing agent required (in parenthesis) are listed below —... 

LiAlH4, lithium tetrahydridoaluminate ("lithium aluminium hydride . so-called) is an excellent reducing agent in ether solution for both organic and inorganic compounds it may be used to prepare covalent hydrides SiH ether, for example... 

Lithium aluminium hydride, LiAlH, is a very active reducing agent, and is used particularly for the ready reduction of carboxylic acids (or their esters) to primary alcohols R-COOH -> R CH,OH. 

Most classical reducing agents leave the pyrimidine nucleus unaffected, as does sodium borohydride lithium aluminium hydride usually gives a di- or tetra-hydro derivative, according to substituent(s) present (70HC(16-S1)322). 

A few reductions using typical hydride reducing agents have been reported for azafulvaleiies. Tlius, lithium aluminium hydride reduces A-methyl-... 

Nonmetallic systems (Chapter 11) are efficient for catalytic reduction and are complementary to the metallic catalytic methods. For example lithium aluminium hydride, sodium borohydride and borane-tetrahydrofuran have been modified with enantiomerically pure ligands161. Among those catalysts, the chirally modified boron complexes have received increased interest. Several ligands, such as amino alcohols[7], phosphino alcohols18 91 and hydroxysulfoximines[10], com-plexed with the borane, have been found to be selective reducing agents. 

Among the complex hydrides, lithium aluminium hydride is the most versatile reducing agent. 

Sodium borohydride is a much milder reducing agent than lithium aluminium hydride and like the latter is used for the reduction of carbonyl compounds like aldehydes and ketones. However, under normal conditions it does not readily reduce epoxides, esters, lactones, acids, nitriles or nitro groups. 

Lithium aluminium hydride (LiAlH4), a strong reducing agent, reduces alkyl halides to alkanes. Essentially, a hydride ion (H ) acts as a nucleophile displacing the halide. A combination of metal and acid, usually Zn with acetic acid (AcOH), can also he used to reduce alkyl halides to alkanes. 

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