Ketones diisobutylaluminum hydride

The milder metal hydnde reagents are also used in stereoselective reductions Inclusion complexes of amine-borane reagent with cyclodexnins reduce ketones to opucally active alcohols, sometimes in modest enantiomeric excess [59] (equation 48). Diisobutylaluminum hydride modified by zmc bromide-MMA. A -tetra-methylethylenediamme (TMEDA) reduces a,a-difluoro-[i-hydroxy ketones to give predominantly erythro-2,2-difluoro-l,3-diols [60] (equation 49). The three isomers are formed on reduction with aluminum isopropoxide... 

The nucleophilic attack on an acceptor-substituted allene can also take place at the acceptor itself, especially in the case of carbonyl groups of aldehydes, ketones or esters. Allenic esters are reduced to the corresponding primary alcohols by means of diisobutylaluminum hydride [18] and the synthesis of a vinylallene (allenene) by Peterson olefination of an allenyl ketone has also been reported [172]. The nucleophilic attack of allenylboranes 189 on butadienals 188 was investigated intensively by Wang and co-workers (Scheme 7.31) [184, 203, 248, 249]. The stereochemistry of the obtained secondary alcohol 190 depends on the substitution pattern. Fortunately, the synthesis of the desired Z-configured hepta-l,2,4-trien-6-ynes 191 is possible both by syn-elimination with the help of potassium hydride and by anti-elimination induced by sulfuric acid. Analogous allylboranes instead of the allenes 189 can be reacted also with the aldehydes 188 [250]. 

Scheme 18.13 Synthesis of the grasshopper ketone (34) according to Eugster and co-workers [46d] (DIBAH = diisobutylaluminum hydride).

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... 

From reduction of aldehydes and ketones Using aluminum-based reagents Diisobutylaluminum hydride-Tin(II) chloride-(S)-l-[l-Methyl-2-pyrrolidinyl] methylpiperidine, 116... 

Shibasaki made several improvements in the asymmetric Michael addition reaction using the previously developed BINOL-based (R)-ALB, (R)-6, and (R)-LPB, (R)-7 [1]. The former is prepared from (R)-BINOL, diisobutylaluminum hydride, and butyllithium, while the latter is from (R)-BINOL, La(Oz -Pr)3, and potassium f-butoxide. Only 0.1 mol % of (R)-6 and 0.09 mol % of potassium f-butoxide were needed to catalyze the addition of dimethyl malonate to 2-cy-clohexenone on a kilogram scale in >99% ee, when 4-A molecular sieves were added [15,16]. (R)-6 in the presence of sodium f-butoxide catalyzes the asymmetric 1,4-addition of the Horner-Wadsworth-Emmons reagent [17]. (R)-7 catalyzes the addition of nitromethane to chalcone [18]. Feringa prepared another aluminum complex from BINOL and lithium aluminum hydride and used this in the addition of nitroacetate to methyl vinyl ketone [19]. Later, Shibasaki developed a linked lanthanum reagent (R,R)-8 for the same asymmetric addition, in which two BINOLs were connected at the 3-positions with a 2-oxapropylene... 

This line of thinking prompted the treatment of 86 with zinc in refluxing methanol for the purpose of generating 88. When this ketone was reduced with diisobutylaluminum hydride in tetrahydrofuran at low temperature, the cis diol 89 was produced with a stereoelectivity in excess of 10 1. Monomesylation of the... 

Diisobutylaluminum benzenetellurolate, prepared from diphenyl ditellurium and diisobutylaluminum hydride, adds in a 1,4-fashion to a,/i-unsaturated aldehydes, ketones, and carboxylic acid esters to give as intermediates /i-phenyltelluro-substituted aluminum enolates that can be hydrolyzed to the carbonyl compounds or reacted with aldehydes to produce aldol adducts2. 

Acid Catalyst. Camphorsulfonic acid (CS A) has been used extensively in synthetic organic chemistry as an acid catalyst. It has particularly been used in protecting group chemistry. For example, hydroxyl groups can be protected as tetrahydropyranyl (THP) ethers using dihydropyran and a catalytic amount of CSA (eq 1). Both 1,2- and 1,3-diols can be selectively protected by reaction with orthoesters in the presence of camphorsulfonic acid to form the corresponding cyclic orthoester (eq 2) This method of protection is particularly useful in that reduction of the orthoester with Diisobutylaluminum Hydride forms the monoacetal, which allows for preferential protection of a secondary alcohol in the presence of a primary alcohol. Ketones have also been protected using catalytic CSA (eq 3). ... 

Cyclopropanation of a,jS-unsaturated AT-methoxy-AT-methylamides 5 with dimethyloxo-sulfonium methanide afforded the cyclopropanecarboxamides 6 in yields far superior to those obtained with the corresponding a,/J-unsaturated ketones. In almost all cases, the trans-isomer was exclusively obtained in analogy to the cyclopropanation of the corresponding unsaturated ketones. The oxygen atom of the methoxy group on the A -methoxy-A -methyl-amide 5 was found to facilitate the reaction. The substituted amides 6 can be converted to ketones (methylmagnesium bromide), aldehydes (diisobutylaluminum hydride) and carboxylic acids (potassium rerf-butoxide/water). It is noteworthy that cyclopropanecarbaldehydes and -carboxylic acids, which are not directly accessible from the corresponding a,)8-unsaturated systems under standard cyclopropanation reactions, can be obtained indirectly by this method. 

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