Lithium aluminum hydride—Cuprous

Lithium aluminum hydride—Cuprous iodide Examples ... 

Cuprous bromide-Sodium bis(2-methoxyethoxyl)aluminum hydride. Lithium aluminum hydride-Cuprous iodide. Potassium tri-sec-butylborohydride. 

Tetrahydrofuran freshly distilled from lithium aluminum hydride should be used. A commercial product with a peroxide content giving a positive iodine test must be treated with about 0.3% of cuprous chloride (boiling for 30 minutes and distillation) before the addition of the hydride. 

Another hydride, magnesium hydride prepared in situ from lithium aluminum hydride and diethylmagnesium, reduced terminal alkynes to 1-alkenes in 78-98% yields in the presence of cuprous iodide or cuprous r rt-butoxide, and 2-hexyne to pure cij-2-hexene in 80-81% yields [///]. Reduction of alkynes by lithium aluminum hydride in the presence of transition metals gave alkenes with small amounts of alkanes. Internal acetylenes were reduced predominantly but not exclusively to cis alkenes [377,378]. 

Alkyl bromides and especially alkyl iodides are reduced faster than chlorides. Catalytic hydrogenation was accomplished in good yields using Raney nickel in the presence of potassium hydroxide [63] Procedure 5, p. 205). More frequently, bromides and iodides are reduced by hydrides [505] and complex hydrides in good to excellent yields [501, 504]. Most powerful are lithium triethylborohydride and lithium aluminum hydride [506]. Sodium borohydride reacts much more slowly. Since the complex hydrides are believed to react by an S 2 mechanism [505, 511], it is not surprising that secondary bromides and iodides react more slowly than the primary ones [506]. The reagent prepared from trimethoxylithium aluminum deuteride and cuprous iodide... 

Triphenylstannane reduced the double bond in dehydro-)J-ionone in 84% yield [872], Complex copper hydrides prepared in situ from lithium aluminum hydride and cuprous iodide in tetrahydrofuran at 0° [873], or from lithium trimethoxyaluminum hydride or sodium bis(methoxy-ethoxy)aluminum hydride and cuprous bromide [874] in tetrahydrofuran at 0° reduced the a,p double bonds selectively in yields from 40 to 100%. Similar selectivity was found with a complex sodium bis(iron tetracarbonyl)hydride NaHFe2(CO)g [875]. 

Since sodium borohydride usually does not reduce the nitrile function it may be used for selective reductions of conjugated double bonds in oc,/l-un-saturated nitriles in fair to good yields [7069,1070]. In addition some special reagents were found effective for reducing carbon-carbon double bonds preferentially copper hydride prepared from cuprous bromide and sodium bis(2-methoxyethoxy)aluminum hydride [7766], magnesium in methanol [7767], zinc and zinc chloride in ethanol or isopropyl alcohol [7765], and triethylam-monium formate in dimethyl formamide [317]. Lithium aluminum hydride reduced 1-cyanocyclohexene at —15° to cyclohexanecarboxaldehyde and under normal conditions to aminomethylcyclohexane, both in 60% yields [777]. 

Tetrahydrofuran was distilled successively from cuprous chloride and sodium wire,5 and further purified by distillation from sodium ben-zophenone ketyl in a recycling still. The checkers used product obtained from Fisher Chemical Company that was distilled from lithium aluminum hydride prior to use. 

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