Diethylaluminium alcoholate

When using the aluminium isopropoxide catalyst to promote the polymerisation of lactide, all three isopropoxide groups have been found to initiate the polymerisation [137,139]. Ring cleavage in the polymerisation with aluminium isopropoxide and diethylaluminium isopropoxide occurred at the C(0)-0 bond, leading to aluminium alcoholate propagating species [139], Lactide polymerisation with other catalysts containing multinuclear species proceeded similarly [138-140]. Analysis of stereosequences of lactide polymers obtained with catalysts such as aluminium isopropoxide, diethylaluminium alcoholate and methylaluminoxane indicates that none of these catalysts favours the formation of isotactic blocks [139]. 

At the same time the conversion of 11/54 — 11/59 (Scheme II/9) was published, an alternative way was found, which is summarized in Scheme II/9. The lithium derivative of (phenylthio)methyl phenyl sulfone adds nearly quantitative into ketones, in the presence of diethylaluminium chloride. The rearrangement (e.g. 11/61—> 11/62) proceeds smoothly on treatment of the tertiary alcohol, 11/61, with an approximately sixfold excess of diethylaluminium chloride [46]. An alternate reagent, the lithium salt of methoxy methyl phenyl sulfone, in a similar reaction yielded, enlarged a-methoxy cycloalkanones. The latter reaction sequence is restricted to the expansion of four- and five-membered rings [46]. 

The enantioselective addition of dialkylzinc reagents to alkynyl aldehydes catalysed by ( )-(+)-(l-methylpyrrolidin-2-yl)diphenylmethanol has been described. Thus the laevorotatory alcohol 102 was obtained in 78% enantiomeric excess (equation 15). The action of diethylaluminium chloride on alkynyllithium compounds yields ether-free diethylalkynylalanes 103, which undergo conjugate addition to nitroalkenes (equation 16). Conjugate addition also occurs in the reactions of (l-alkynyl)diisopropoxyboranes 104 (R = Bu, t-Bu or Ph) with a,j5-unsaturated ketones 105 (R = H, Me or Ph R = Me, hexyl or Ph) (equation 17). ... 

Isomerization of epoxides to allylic alcohols can be carried out under mild conditions using diethylaluminium dialkylamides (usually prepared in situ). A useful conversion of olefins into allylic acetates or ethers involves treatment of the olefin with phenyl selenyl bromide or chloride, addition of an alcohol or acid to give a P-substituted selenide (139), and selective oxidative elimination e.g. truns-cyclodode-cene gave 3-acetoxy-trans-cyclododecene in 85% yield. 

Diethylaluminium amides R2NAlEt2 add to epoxides to give, after hydrolysis, rans-l,2-amino-alcohols ° and Scheme 13 shows the result of addition of dialkylaluminium benzenethiolates to a,/3-unsaturated epoxides the major product is that in which the R groups have cw-stereochemistry. ... 

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