Diisobutyl aluminium hydride

The higjily water-soluble dienophiles 2.4f and2.4g have been synthesised as outlined in Scheme 2.5. Both compounds were prepared from p-(bromomethyl)benzaldehyde (2.8) which was synthesised by reducing p-(bromomethyl)benzonitrile (2.7) with diisobutyl aluminium hydride following a literature procedure2.4f was obtained in two steps by conversion of 2.8 to the corresponding sodium sulfonate (2.9), followed by an aldol reaction with 2-acetylpyridine. In the preparation of 2.4g the sequence of steps had to be reversed Here, the aldol condensation of 2.8 with 2-acetylpyridine was followed by nucleophilic substitution of the bromide of 2.10 by trimethylamine. Attempts to prepare 2.4f from 2.10 by treatment with sodium sulfite failed, due to decomposition of 2.10 under the conditions required for the substitution by sulfite anion. 

The Stephen s method allows the reduction of nitriles by stannous chloride in acid medium. If the amine chlorhydrate initially formed is hydrolyzed, the corresponding aldehyde is obtained (37, 91). Harington and Moggridge (37) have reduced 4-methyl-5-cyanothiazole by this method (Scheme 23). However, Robba and Le Guen (91) did not obtain the expected products with 4.5-dicyanothiazole and 2-methyl-4,5-dicyanothiazole. These compounds have been reduced with diisobutyl-aluminium hydride with very low yields (3 to 6%) (Scheme 24). In other conditions the reaction gives a thiazole nitrile aldehyde with the same yield as that of the dialdehyde. 

Detty published the first example of the titled approach in his pioneering work on teluropyrans (88MI1). The hexafluorophosphate 76 was reduced with diisobutyl aluminium hydride (DIBAL-H) to a 93 7 mixture of isomeric teluropyrans 77 and 78 accompanied by traces (ca. 1%) of the dimeric product 80. The latter was also obtained after the electrochemical reduction of 76 via radicals 79 or by a modification of the reduction with DIBAL-H (Scheme 5). 

Since sulphones 204 are easily available compounds one would expect that they could be used as starting materials for the preparation of sulphoxides via the selective removal of one oxygen atom from the sulphonyl group (equation 112). Up to now, there is only one example reported of a direct reduction of a sulphone to a sulphoxide. The bicyclic dideuterio sulphone 205 after 24 h treatment with three-fold excess of diisobutyl aluminium hydride in boiling dichloromethane gave the corresponding sulphoxide 206 in 36% yield (equation 113). A two-step procedure for the selective reduction of sulphones to sulphoxides, which involves an initial reaction of sulphone 204 with aryldiazonium tetrafluoroborate 207 to form aryloxysulphoxonium salt 208 and its subsequent reduction (equation 114), was alluded to by Shimagaki and coworkers and... 

Di-tert-butyl-4H-tellurin A solution of 1.60 g (5.0 mmol) of 2,6-di-ferf-butyl-4-oxo /7-tellurin in 15 mL dry tetrahydrofuran is placed into a flame-dried, 50 mL, two-necked flask equipped with a rubber septum cap and a dry-argon inlet. The flask is cooled to 0°C 7.5 mL of a 1.5 M solution (10.5 mmol) of diisobutyl aluminium hydride in toluene are dropped to the cold solution with the help of a syringe. The reaction is quenched by addition of 10 mL of moist diethyl ether. The resulting solution is poured into 100 mL diethyl ether. The organic phase is washed with three 25 mL portions of 5% hydrochloric acid and then with two 50 mL portions of brine, dried with anhydrous sodium sulphate, filtered and the filtrate concentrated. Cold pentane (5 mL) is added to the residual oil and the mixture is cooled to -20°C. The pentane is decanted from the yellow aystals. The decantate is chromatographed on sihca gel with dichloromethane as the mobile phase to give a yellow oil. Yield 62%. 

Oxidation of the hydroxyl group in 186 with pyridinium chlorochromate (PCC) in CH2CI2 affords the aldehyde 197. The reduction of 197 back to 186 is possible in EtOH in the presence of TiCl4, whereas upon treatment of 197 with diisobutyl-aluminium hydride a competitive reaction with the fullerene core was observed. 

Stronger hydrides can reduce carbonyl groups of dihydropyrimidinediones, and thus both L1A1H4 and diisobutyl-aluminium hydride regioselectively gave the 4-hydroxy derivative 540 on reduction of the 5,6-dihydro-2,4-pyrimidi-nedione 539 <2001TL8629>. 

The aldehyde moiety of 50 can be condensed with either amines or active methylene compounds. In the case of reactions with amines, the aldehyde 50 (presumably obtained by reduction of the cyano group with diisobutyl-aluminium hydride (DIBAL-H)) forms simple Schiff bases 51 (Equation 20) <1998J(P1)3557>. 

The reaction of 6-methylpyridine-3-carboxylic acid methyl ester with N,0-dimethylhydroxylamine and isopropyl-magnesium chloride in toluene gives the N-methoxyamide derivative (x), which is reduced with diisobutyl aluminium hydride (DIBAL) to afford 6-methylpyridine-3-carbaldehyde (xi). The reaction of the aldehyde (xi) with a phosphite provides the diphenyl phosphonate derivative, which is condensed with 4-(methylsulfonyl)benzaldehyde in the presence of potassium fe/f-butoxide in HF to yield the enimine (xii). Finally, this compound is hydrolyzed with HCI to yield the ketosulfone (ix). 

The prepolymer was synthesized from AIBN and polyethylene glycol (M = 300) b Diisobutyl aluminium hydride... 

Two pseudo-sugars of P-L-allo and a-D-manno have been prepared from the preceding intermediate 143 as follows. Reduction of 143 with diisobutyl aluminium hydride afforded the 3-hydroxyl derivative (155), which gave the 3-O-acetyl derivative (156) on acetylation. Hydroxylation of 156 with osmium tetroxide and hydrogen peroxide gave the compound (157), m.p. 154-155 °C, [a] 1 +71.5° (chloroform), as a main component (53% yield) and an unidentified compound, m.p. 191-193 °C, [a.] —7.9° (chloroform), as a minor component (6% yield). On acetylation, 157 was converted into the tri-0-acetyl derivative (158), m.p. 66-67 °C, [a]23 +41.8° (chloroform). 

Fig. 6. Nicolaou s total synthesis construction of the maleic anhydride moiety. KHMDS = potassium hexamethyldisilazide, DIBAL = diisobutyl-aluminium hydride, acac = acetylacetonate, Ms = methanesulfonyl.

With a milder reducing agent like DIB AH (diisobutyl-aluminium hydride), the reaction stops after the addition of one hydride ion, and an aldehyde is obtained instead (RCHO). 

Two isobutyl groups are present in the reducing agent diisobutyl aluminium hydride (DIBAL). 

Like the silyl ethers, the stability of the silyl esters parallels the steric bulk of the substituents on the silicon atom. Tris(2,6-diphenylbenzyl)siiy1 esters confer extraordinary steric protection upon the carboxyl group.234 For example, the tris(2,6-diphenylbenzyl)silyl ester of 4-phenylbutanoic acid 104.1 [Scheme 6.104] does not react with butyllithium (2.5 equiv) after 5 h at -78 °C or methylmag-nesium bromide (2,5 equiv) at room temperature. Nor did it react with lithium aluminium hydride after 30 min at 0 °C l M HC1 in THF at 40 °C, or aqueous sodium hydroxide at 50 °C after 5 h. Ester 104.1 was reduced with diisobutyl-aluminium hydride in 99% yield to give the 4-phenyl-l-butanol (99%) and HF pyridine in THF (1 2) at 50 aC cleaved it back to the acid after 5 h. Unfortunately, the penalty for such unusual stability is high the tris(2 6-diphenyl-... 

SYNS AL-ALCHILI (ITALIAN) AL-DIISOBUTYL BIS(ISOBUTYL)HYDROALUMINUM DIISOBUTYL-ALUMINIUM HYDRIDE DIISOBUTYLALUMINUM HYDRIDE HYDROBIS(2-METHYLPROPYL)-ALUMINUM HYDRODIISOBUTYLALUMINUM... 

Vinyloxiranes are reduced very selectively by diisobutyl-aluminium hydride (Eq. 168). Without regard to the configuration (exo,endo), the reduction of norborn-ane diepoxides with LiAlH proceeds in such a manner that the norbornane moiety remains intact in the reaction. (Eq. 168). ... 

Zakharkin, L.L, and Khorlina, I.M., Preparation of aldehydes by reduction of nitriles with diisobutyl-aluminium hydride, Dokl. Akad. Nauk SSSR, Ser. Khim., 116,422,1957 Chem. Abstr, 52, 8040f. 1958. 

Alken-(l)-yl-oxirane liefern bei der Reduktion mit Alkalimetall/fl. Ammoniak vor-zugsweise die (E)-Allylalkohole, wahrend bei Reduktion mit Diisobutyl-aluminium-hydrid als Hauptprodukt das (Z)-Isomere entsteht8 so erhalt man z.B. aus... 

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