DIBALH diisobutylaluminum

A more general route to 4-acetoxy-l,3-dioxanes utilizes the reductive acylation of l,3-dioxane-4-ones [46] (Scheme 21). l,3-Dioxane-4-ones 126 are prepared from the corresponding -hydroxy carboxylic acids. Low temperature reduction with DIBALH generates a diisobutylaluminum hemiacetal (127) which undergoes acylation in situ with AC2O in the presence of pyridine and DMAP. This method allows for the preparation of a wide range of 4-acetoxy-l,3-dioxanes, without the problem of a-epimerization. This method also represents a general approach to acylic a-acetoxy ethers, which are themselves useful synthetic intermediates [47,48]. 

Alkyl derivatives of boron and alane can function as reducing reagents in a similar fashion. Two reagents of this type, disiamylborane and diisobutylaluminum hydride (DiBAlH) are included in Table 5.3. The latter is an especially useful reagent. 

The most widely used reagent for partial reduction of esters and lactones at the present time is diisobutylaluminum hydride (DiBAlH).83 By use of a controlled amount of the reagent at low temperature, partial reduction can be reliably achieved. The selectivity results from the relative stability of the hemiacetal intermediate that is formed. The aldehyde is not liberated until the hydrolytic workup and is therefore not... 

In aprotic solvents, such as dichloromethane and THF, potassium boro-hydride [10], lithium borohydride [8b], lithium triethylborohydride [8a, 11], and diisobutylaluminum hydride (DIBALH) [11] have been used instead of NaBH4. NaBH4 also reduces elemental selenium in alcohol or water to sodium hydrogen selenide or sodium diselenide (Na2Se2) depending on the stoichiometry of the reactants (Scheme 8) [12]. These anions are useful for the synthesis of selenides or diselenides, respectively, via nucleophilic substitution with various electrophiles. 

Diisobutylaluminum phenylselenolate (39), which is prepared in situ by the reaction between diphenyl diselenide and diisobutylaluminum hydride (DIBALH) [67], is also a useful nucleophilic selenium reagent (Scheme 37). For example, 39 reacts with oxime sulfonates to produce selenoimidic esters... 

Chemists have found that if diisobutylaluminum hydride (DIBALH) is used as the hydride donor at a low temperature, the reaction can be stopped after the addition of one equivalent of hydride ion. This reagent, therefore, makes it possible to convert esters into aldehydes, which is initially surprising, since aldehydes are more reactive than esters toward hydride ion. 

Diisobutylaluminum hydride. 13, 115-116 15, 137-138 16, 134-135 17, 123-125 Monosilyl acetals and amines. The DIBALH reduction products of esters can be converted into monosilyl acetals by treatment with TMSOTf-pyridine and those of nitriles into amines by the addition of organolithium reagents. ... 

The reduction of thiol esters to aldehydes using Raney nickel was reported to proceed in 70-80% ethanol under reflux more than five decades ago. [38] Fujita and co-workers developed a low temperature (-20 to -50 °C) reduction of thio esters by treating with diisobutylaluminum hydride (DIBALH) in hexane-dichlorometane (Eq. 17) [39]. The authors also reported that treatment of thiol esters with NaBH4 in aqueous THF at room temperature gave alcohols in high yields (Eq. 18). 

Reduction of an esfer to a primary alcohol can be viewed as two successive hydride ion transfers, as shown in the mechanism we just presented. Chemists wondered if it might be possible to modify the structure of the reducing agent to reduce an ester to an aldehyde and no further. A useful modified hydride-reducing agent developed for this purpose is diisobutylaluminum hydride (DIBALH). 

Reduction by diisobutylaluminum hydride (DIBALH) at low temperature gives an aldehyde and an alcohol. 

The reagent diisobutylaluminum hydride (DIBALH) reduces esters to aldehydes. When nitriles are treated with DIBALH followed by mild acid hydrolysis, the product is also an aldehyde. Propose a mechanism for this reduction. 

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