Reducing agents diisobutylaluminum hydride

The aldehyde intermediate can he isolated if 1 equivalent of the less reactive reducing agent diisobutylaluminum hydride (DIBAH) is used instead of LiAlH4. The reaction is carried out at 78 °C to avoid further reduction to the alcohol. Such partial reductions of carboxylic acid derivatives to aldehydes also occur in numerous biological pathways, although the substrate is either a thioester or an acyl phosphate rather than an ester. We ll see an example in Section 16.8. 

Esters are reduced to aldehydes using the mild reducing agent diisobutylaluminum hydride (DIBAL). To avoid subsequent reduction of the aldehyde, exactly one equivalent of the reagent is used, and the reaction is carried out at —78 °C. 

Reducing agents Aluminum hydride. Bis-3-methyl-2-butylborane. n-Butyllithium-Pyridine. Calcium borohydride. Chloroiridic acid. Chromous acetate. Chromous chloride. Chromous sulfate. Copper chromite. Diborane. Diborane-Boron trifluoride. Diborane-Sodium borohydride. Diethyl phosphonate. Diimide. Diisobutylaluminum hydride. Dimethyl sulfide. Hexamethylphosphorous triamide. Iridium tetrachloride. Lead. Lithium alkyla-mines. Lithium aluminum hydride. Lithium aluminum hydride-Aluminum chloride. Lithium-Ammonia. Lithium diisobutylmethylaluminum hydride. Lithium-Diphenyl. Lithium ethylenediamine. Lithium-Hexamethylphosphoric triamide. Lithium hydride. Lithium triethoxyaluminum hydride. Lithium tri-/-butoxyaluminum hydride. Nickel-aluminum alloy. Pyridine-n-Butyllithium. Sodium amalgam. Sodium-Ammonia. Sodium borohydride. Sodium borohydride-BFs, see DDQ. Sodium dihydrobis-(2-methoxyethoxy) aluminate. Sodium hydrosulflte. Sodium telluride. Stannous chloride. Tin-HBr. Tri-n-butyltin hydride. Trimethyl phosphite, see Dinitrogen tetroxide. 

Alkyl derivatives of borane and alane can function as reducing agents in a similar fashion. Two reagents of this group, disiamylborane and diisobutylaluminum hydride (DIBA1H), are included in Table 5.3. The latter is an especially useful reagent. 

Support-bound aldehydes or ketones can be reduced to alcohols under mild reaction conditions that are compatible with most supports and linkers. Typical reducing agents are sodium borohydride or diisobutylaluminum hydride, which can penetrate cross-linked polystyrene provided that a solvent with sufficient swelling ability is... 

The isoquinoline ring has been shown to be selectively reduced to the dihydro- or tetrahydroisoquinoline by diisobutylaluminum hydride, depending upon the ratio of reducing agent employed. The reaction has been employed to prepare 1,2-dihydroisoquinoline or... 

Acid chlorides are more reactive than other acid derivatives, and they are reduced to aldehydes by mild reducing agents such as lithium tri-ferf-butoxyaluminum hydride. Diisobutylaluminum hydride (DIBAL-H) reduces esters to aldehydes at low temperatures, and it also reduces nitriles to aldehydes. These reductions were covered in Sections 18-9,18-10, and 20-13. 

Hydride reductions of (7) can be controlled to give either the (R) or (5) secondary hydroxy compound with good selectivity by choice of the reducing agent. Lithium Tri-s-butylborohydride (L-Selectride ) provided the (5)-alcohol (according to Cram s chelate rule) and Diisobutylaluminum Hydride (DIBAL) gave the (R)-carbinol in excess (eq 7). The DIBAL results were rationalized in terms of the open-chain Comforth dipole model. ... 

Efficient conjugate reduction of several a,/8-unsaturated carbonyl substrates was similarly realized by combining ATPH with diisobutylaluminum hydride-BuLi ate complex (DIBAH-BuLi) as a reducing agent [144]. Diisobutylaluminum hydride-t-BuLi was more effective for the 1,4 reduction of a,/ -unsaturated aldehydes, as illustrated in Sch. 105. 

Diisobutylaluminum hydride (DIBAH) is undoubtedly one of the most common reducing agents in organic synthesis and recent interest in the synthetic utility of DIBAH has been directed toward diastereoselective reduction of carbonyl substrates. High, i-syn diastereoselectivity has been achieved in the chelation-controlled reduction of P-hydroxy ketones with DIBAH in THF [49], The choice of solvents strongly affects the selectivity. Use of CH2CI2 or toluene in place of THF did not show any diastereoselectivity. 

The complex is obtained from tri-n-butylphosphine and copper(I) hydride, prepared by reduction of copper(I) bromide with diisobutylaluminum hydride at —50°. The complex is a useful reducing agent it reduces iodobenzene to benzene (80% yield) and benzoyl chloride to benzaldehyde (50% yield). In addition the complex reduces primary, secondary, and tertiary alkyl-, vinyl-, and arylcopper(l) compounds to the corresponding hydrocarbons in high yields, under mild conditions and with no rearrangements.1... 

While most reducing agents lead to the expected bornylamines as products of the reduction of camphor oxime (see above), diisobutylaluminum hydride is a notable exception, as a ring-enlarged amine, (1/ ,47 )-1.8,8-trimethyl-2-azabicyclo[3.2.1]octane (67) is obtained in high yield when starting with the oxime of (+ )-camphor16, It has been used as the lithium salt in enantioselective deprotonation and elimination reactions (Section C.). 

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