Aluminium isopropoxide

In the following preparation to illustrate the Meen.vein-Pormdorf-Verley reduc tion, a solution of benzophenone in isopropanol is rapidly reduced in the presence of aluminium isopropoxide to benzhydrol (CaHs)2CO (C Hj)jCH OH. It is clear that the aluminium isopropoxide must take some essential part in this reaction, for benzophenone when dissolved even in cold isopropanol with a trace of acetic acid is reduced to tetraphenylethyleneglycol (p. 150). 

The mechanism of the reduction remains uncertain. The work of E. D. Williams, K. A. Krieger and A. R. Day (1953) using deuterium-labelled aluminium isopropoxide, shows that hydrogen atoms are transferred predominantly from the central carbon atom of an isopropoxide group to the carbon atom of the carbonyl group undergoing reduction, the process probably involving a cyclic complex ... 

Aluminium isopropoxide can be obtained as a fine powder from technical sources. When the bottle has once been opened however, the stopper should be firmly replaced and covered with wax more conveniently, the stoppered bottle can be kept in an atmospheric desiccator over calcium chloride or sodium hydroxide, preferably in the dark. 

It is advisable in any case before an experiment to place the weighed aluminium isopropoxide overnight in a shallow dish in a vacuum desiccator over sodium hydroxide. The isopropanol should be dried over anhydrous sodium sulphate, and the clear liquid decanted off before use. 

Place in the flask 2 g. of benzophenone, 15 ml. of isopropanol and 2 5 g. of aluminium isopropoxide. This mixture has now to be heated gently under reflux so that the temperature registered by the thermometer in the column does not exceed 80°, i.e., so that only acetone distils. For this purpose, the flask should preferably be heated in an oil-bath direct heating, even over an asbestos sheet, may cause local overheating and decomposition the use of a water-bath on the other hand may make the column undesirably damp. 

The reagent is conveniently stored as a solution in isopropyl alcohol. The molten (or solid) alkoxide is weighed out after distillation into a glass-stoppered bottle or flask and is dissolved in sufficient dry isopropyl alcohol to give a one molar solution. This solution may be kept without appreciable deterioration provided the glass stopper is sealed with paraffin wax or cellophane tape. Crystals of aluminium isopropoxide separate on standing, but these may be redissolved by warming the mixture to 65-70°. 

Prepare a solution of aluminium isopropoxide from 23 -5 g. of aluminium, 0-5 g. of mercuric chloride and 250 ml. of dry isopropyl alcohol ... 

It is possible to reduce thiazole carbonyl derivatives with aluminium isopropoxide (56, 57). For example, 4-methyl-5-acetylthiazole gives 4-methyl-5-(a-hydroxyethyl)thiazole. With aluminium amalgam one obtains a duplication like to the pinacol reaction, and the yield is genaally poor... 

The reduction of thiazole carboxaldehydes with isopropanol and aluminium isopropoxide gives the corresponding alcohols (37, 107, 108). 

Reduction with aluminium isopropoxide by the Meerwein-Pondorf procedure yields the alcohol (56, 57, 112). 

Hydroxy-1,2,3,4-tetrahydrocrysene (2) A mixture of 4-keto-1,2 3 4-tetrahydrocrysene 1 (2 75 g, 11 mmol) and aluminium isopropoxide (8 2 g, 40 mmol) in PhMe (25 mL) was refluxed for 1 h After cooling, iPrOH (25 mL) was added and the formed acetone was distilled slowly maintaining the volume constant by addition of iPrOH After all acelone was distilled, the solution was acidified with 0% H2SO4 The separated toluene solution was evaporated to gwe 2 1 g of 2 (76%), mp 156-158 C... 

Meerwein-Pondorff reduction is the synthesis of alcohols by heating carbonyl compounds with aluminium isopropoxide in isopropanol and distilling off acetone by-product... 

Oxathiine derivatives lb 301,304 Oxathizine fungicides la 44 Oxazepam la 364 Oxazolidinthione derivatives lb 301 Oxeladine citrate lb 327 Oxidation, aluminium isopropoxide la 59 -, atmospheric oxygen la 60 -, chromic acid la 59, 60 -, hydrogen peroxide la 59 -, iodine la 60... 

Two kinds of solution were prepared in advance. Solution A was a water solution containing an Si source, which was obtained by hydrolyzing metal alkoxide (tetraethylorthosilicate, TEOS) with a dilute tetrapropylammoniumhydroxide (TPA-OH)/water solution at room temperature. The molar ratio of Si to the template was 3. In peparation of ZSM-S zeolite nanoerystals, aluminium isopropoxide as an A1 source and sodium chloride were added into solution A. Solution B was an oi mic solution containing surfectant Nonionie surfactants, poljraxyethylene (15) cxslylether (C-15), polyoxyethylene (15) nonylphenylether (NP-15), and polyoxyethylene (15) oleylether (O-15), and ionic surfoctnnts, sodium bis(2-ethylhexyl) sulfosucdnate (AOT) and... 

In order to prepare ZSM-5 zeolite nanocrystals, an A1 source of aluminium isopropoxide was added into solution A, and hydrothermal synthesis of the solution A containing Si and A1 sources was carried out in an 0-15/cyclohexane solution at 120 degree C for 50 h. Figures 4 show ac-NHj-TPD spectra and a SEM photograph of the ZSM-5 zeolite nanocrystals. Nanocrystals with a diameter of approximately 150 nm were observed, and the NH3-TPD spectrum showed desorption of NHj above 600 K, indicating that the nanocrystals possessed strong acid sites. 

Aluminium isopropoxide, Crotonaldehyde Wagner-Jauregg, T., Angew. Chem., 1939, 53, 710... 

Dining distillation of 2-propanol recovered from the reduction of crotonaldehyde with isopropanol/aluminium isopropoxide, a violent explosion occurred. This was attributed to peroxidised diisopropyl ether (a possible by-product) or to peroxidised crotonaldehyde. An alternative or additional possibility is that the isopropanol may have contained traces of a higher secondary alcohol (e.g. 2-butanol) which would be oxidised during the Meerwein-Ponndorf reduction procedure to 2-butanone. The latter would then effectively sensitise the isopropanol or other peroxidisable species to peroxidation. 

Aluminium isopropoxide, Heavy metal salts Ward, D. S., unpublished information, 1974... 

Aluminium isopropoxide is a specific reagent for the reduction of carbonyl group to hydroxyl group. Since it reduces the carbonyl group in presence of other reducible groups like nitro or a double bond which remain unaffected, aluminium isopropoxide is largely employed for the reduction of unsaturated aldehydes and ketones. 

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