Lithium aluminum hydride alkyl halide reduction

A thio-substituted, quaternary ammonium salt can be synthesized by the Michael addition of an alkyl thiol to acrylamide in the presence of benzyl trimethyl ammonium hydroxide as a catalyst [793-795]. The reaction leads to the crystallization of the adducts in essentially quantitative yield. Reduction of the amides by lithium aluminum hydride in tetrahydrofuran solution produces the desired amines, which are converted to desired halide by reaction of the methyl iodide with the amines. The inhibitor is useful in controlling corrosion such as that caused by CO2 and H2S. 

Protodehalogenation.1 This hydride is the reagent of choice for hydrogenolysis of alkyl halides. Lithium aluminum hydride is somewhat less powerful, particularly for reduction of alkyl chlorides. 

Primary and secondary alkyl bromides, iodides, and sulfonates can be reduced to the corresponding alkanes with LiBHEt3 (superhydride) or with lithium aluminum hydride (LiAlH4, other names lithium tetrahydridoaluminate or lithium alanate). If such a reaction occurs at a stereocenter, the reaction proceeds with substantial or often even complete stereoselectivity via backside attack by the hydride transfer reagent. The reduction of alkyl chlorides to alkanes is much easier with superhydride than with LiAlH4. The same is true for sterically hindered halides and sulfonates ... 

Formation and Reduction of Nitriles Like the azide ion, cyanide ion (- C=N ) is a good Sn2 nucleophile it displaces leaving groups from unhindered primary and secondary alkyl halides and tosylates. The product is a nitrile (R—C=N), which has no tendency to react further. Nitriles are reduced to primary amines by lithium aluminum hydride or by catalytic hydrogenation. 

Reductive dehalogeuation of alkyl halides. Lithium aluminum hydride has commonly been used only for reductive dchalogenation of reactive substrates organotin hydrides, for example tri- -btityltin hydride (I. 1192-1193 2, 424 3, 294), have been used for reduction of inert halides. Recently JeflToid ei al. have reported that supposedly inert halides are reducible by lithium aluminum hydride. Thus the vinyl halide (I) is reduced to (2, endb-2-phenylbicyclo[3.2. l]octene-3) by lithium aluminum hydride in refluxing ether (24 hr.). 3-Bromobicyclo[3.2.l]octene-2 is reduced to the parent... 

The ability of reducing agents, such as lithium aluminum hydride, to reduce halides and sulfonates to their corresponding alkyl derivatives is well known. Lithium aluminum hydride is also selective for the reduction of primary halides and sulfonates over secondary analogs. As shown in Scheme 6.70, this reaction was applied to a bis-tosylate with the major isolated product being the mono-tosylate with deoxygenation at C-6 [109]. 

Lithium aluminum hydride (LAH) reductions are carried out in aprotic solvents and give rise to the dihydro- and tetrahydropyridine derivatives. LAH reacts with both pyridines and pyridinium salts. It has been known for some time that aged ( 24 h) pyridine and LAH solutions form complexes of lithium tetrakis(A -dihydropyridinyl)aluminate (40, LDPA), - which is believed to consist of a mixture of the 1,2- and 1,4-dihydropyridines (by NMR). Indeed, LDPA itself has been used as a selective reducing agent for ketones and affords 3-substituted pyridines (41) on reaction with alkyl halides. 2,5-Dihydropyridines have been identified as intermediates in similar reactions. Kuthan and co-workers have shown that for 3,5-dicyan-... 

Halides and tosylates. Trevoy and W. G. Brown found that lithium aluminum hydride reduces benzyl iodide and benzyl bromide in high yield at 35° in either diethyl ether or tetrahydrofurane. In tetrahydrofurane at 65°, benzyl chloride and 1 -bromodecane are reduced to toluene and to n-decane, both in 72% yield. Johnson, Blizzard, and Carhart found that lithium aluminum hydride reacts more sluggishly than in other reductions and presented experimental evidence that not all four hydrogen atoms possess adquate reactivity toward alkyl halides. Thus the reaction probably proceeds in at least two steps, the first of which is much more rapid than... 

Reduction of aikyi azides (Section 22.10) Alkyl azides, prepared by nucleophilic substitution by azide ion in primary or secondary alkyl halides, are reduced to primary alkylamines by lithium aluminum hydride or by catalytic hydrogenation. 

Reduction of halides. Primary, secondary, and certain tertiary halides and tosylates can be selectively reduced by sodium borohydride in DMSO or sulfolane. 1,2-Dibromides are reduced to hydrocarbons in moderately good yields. The method complements that of Bell and Brown,2 which uses sodium borohydride in 65% aqueous diglyme for reduction of secondary and tertiary alkyl halides which are capable of forming relatively stable carbonium ions (1, 1054). Lithium aluminum hydride reduction affords only olefins. Reduction of optically active tertiary alkyl halides proceeds with racemization, presumably by way of an elimination-addition mechanism.3... 

Good yields of phenylarsine [822-65-1], C H7As, have been obtained by the reaction of phenylarsenic tetrachloride [29181-05-1], C6H5AsC14, or phenyldichloroarsine [696-28-6], C HcAsCT, 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 halide. Thus methylarsine [595-52-2], CH5As, is obtained in 80% yield (43) ... 

C.vi. Alkyl Halides. Alkyl halides are reduced by lithium aluminum hydride to give a hydrocarbon in what is known as a hydrogenolysis reaction (R3C—X R3C—H sec. 4.8.E).6l Reduction of 1-bromobutane... 

---