Organoaluminum compounds with alcohols

Early attempts by Asinger to enlarge the scope of hydroalumination by the use of transition metal catalysts included the conversion of mixtures of isomeric linear alkenes into linear alcohols by hydroalumination with BU3AI or BU2AIH at temperatures as high as 110°C and subsequent oxidation of the formed organoaluminum compounds [12]. Simple transition metal salts were used as catalysts, including tita-nium(IV) and zirconium(IV) chlorides and oxochlorides. The role of the transition metal in these reactions is likely limited to the isomerization of internal alkenes to terminal ones since no catalyst is required for the hydroalumination of a terminal alkene under these reaction conditions. 

Nickel catalysts are well-known to promote hydroalumination of olefins, and the resulting organoaluminum compounds can be converted to the corresponding alcohols through oxidation with molecular oxygen [97J. 

Reaction with epoxy aiochols-3 Epoxides formed from (E)-allylic alcohols react regioselectively with organoaluminum compounds to provide 1,2-diols with inversion at C j in high yield. 

If organoaluminum compounds contact skin, they cause persistent bums. Their 40% solutions cause heavy bums (5-10% solutions do not). If an organoaluminum compound contacts skin, it should be washed away with petrol or kerosene (not water ) within the first 5-8 seconds of contact later washing is not so effective. The affected area is wiped with alcohol and bandaged. 

With other reactive donors such as alcohols, aldehydes, ketones, and carboxylic acids, organoaluminum compounds also form 1 1 adducts. Generally, however, these are not isolable, since the functional groups react further (cf. Section V,D). In a few cases, such 1 1 adducts can be identified, e.g., between triphenylalane and benzophenone (176) or benzonitrile (175a, 204) at room temperature or between diethylaluminum bromide and alcohols, aldehydes, ketones, or carboxylic acids at —80°C (217). 

In general all A1—H and A1—C bonds in organoaluminum compounds react quantitatively at or below room temperature with water and alcohols to form compounds with A1—O bonds. Thus trialkyl alanes with alcohols produce aluminum alcoholates and alkanes. Reaction between water or most of the lower alcohols (methanol, ethanol) and trialkyl alanes with small alkyl groups is usually explosive if the undiluted components are mixed at room temperature. If certain safety precautions are observed, however, it is possible to carry out the hydrolysis (or deuterolysis for analytical purposes) so as to obtain the corresponding hydrocarbons. Ether solutions are particularly advantageous as the etherates of trialkyl alanes react less vigorously than the free compounds. 

First they treat such an olefin with an organoaluminum compound, obtaining the primary alkylaluminum then oxidation with air or oxygen leads to an aluminum alkoxide which on hydrolysis gives the primary alcohol, e.g. ... 

Asymmetric Ene Reaction Catalyzed by Chiral Organoaluminum ReagentP The asymmetric ene reaction of carbonyl compounds with alkenes provides a valuable access to optically active homoallylic alcohols. Using the same chiral catalyst, an asymmetric ene reaction of prochiral aldehydes and alkenes was achieved as shown below ... 

C-3 attack predominantly takes place in the reaction of 2,3-epoxy alcohols with organoaluminum compounds such as MesAl, PhC CAlEta, Me3SiC < AlEt2, Bu 2AlH and Bu aAl. The yield and stereochemical outcome depend on the substrates and organoaluminum reagents used. ... 

As reported earlier for porphyrin salts, protic reversible chain transfer agents, generally alcohols, can be used in association with aluminum porphyrin/bulky organoaluminum compound systems, reducing significantly the amount of aluminum in the polymer. Coordination of the Lewis acid to the alcohol increases alcohol acidity and accelerates exchange... 

Practical applications of organoaluminum derivatives of alcohols with -NR2 donor termini have begun to be exploited in recent years. Thus, [R2Al(n-0, R )]2 compounds have proven to be useful reagents for C-C bond formation [130, 131, 288]. More recently, new chiral Al(IIl) complexes derived from readily accessible Cinchona alkaloids have been used as unprecedented building blocks for the... 

Alkylation of enolizable carbonyl compounds. fi-Oxo amides react with organoaluminum chlorides stereoselectively to give alcohol products ... 

Polar compounds (water, oxygen-, nitrogen-, and sulfur-containing compoimds). They react with the organoaluminum co-catalyst (water, alcohols, amines, thiols), complex the aluminum center in a Lewis acid/base interaction (ketones, ethers, thioefhers), or coordinate strongly to the nickel catalytic center (amines, sulfur compounds). They reduce the concentration of the active species and may be responsible of the formation of sludges in the reaction section. 

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