Acids Organoaluminum reagents

Although aliphatic Claisen rearrangements normally requires high temperatures, in the presence of Lewis acidic organoaluminum reagents, the rearrangement has been accomplished under very mild conditions, as discussed in the previous section. 

This chapter presents the concentrated overview concerning the recent advances of such organic reactions induced by Lewis acidic organoaluminum reagents. 

Other than listed above, new entries of oxygen-containing electrophiles were reported to react with Lewis acidic organoaluminum reagent in this decade. Demir... 

The 3.8-nonadienoate 91, obtained by dimerization-carbonylation, has been converted into several natural products. The synthesis of brevicomin is described in Chapter 3, Section 2.3. Another royal jelly acid [2-decenedioic acid (149)] was prepared by cobalt carbonyl-catalyzed carbonylation of the terminal double bond, followed by isomerization of the double bond to the conjugated position to afford 149[122], Hexadecane-2,15-dione (150) can be prepared by Pd-catalyzed oxidation of the terminal double bond, hydrogenation of the internal double bond, and coupling by Kolbe electrolysis. Aldol condensation mediated by an organoaluminum reagent gave the unsaturated cyclic ketone 151 in 65% yield. Finally, the reduction of 151 afforded muscone (152)[123]. n-Octanol is produced commercially as described beforc[32]. 

Group 14 metal halides also undergo metathesis reactions. For instance, organotin compounds are prepared on an industrial scale using organoaluminum reagents. These reactions take place because tin is a softer Lewis acid than aluminum, and carbon (in an alkyl group, represented by R) is a softer Lewis base than chlorine ... 

The asymmetric synthesis of / -branched carboxylic acid derivatives was accomplished by conjugate addition of mixed organoaluminum reagents to optically active Arabinose-derived c -unsaturated A-acyloxazolidinones (Scheme 47). Efficient stereocontrol was achieved using different optically active bicyclic oxazolidinones, yielding (.R)- or ( -configured / -branched carboxylic acid derivatives.136a... 

Substitution of sulfonesJ Organoaluminum reagents, particularly vinyl- or alkynylalanes, undergo Lewis acid catalyzed substitution reactions with sulfones. Thus the vinylalane 2 reacts with the allylic sulfone 1 in the presence of A1C13 to... 

An even greater steric effect of the Lewis acid catalyst is observed with the organoaluminum reagents 4-6 in the Diels-Alder reactions of an aldehyde with a diene (equation III). 

In all of the above processes, the organoaluminum compounds serve as cocatalysts that activate a transition metal for the desired organic transformations. There are several important processes that do not involve transition metals and in which the organoaluminum reagents acts as a catalyst or stoichiometric reagent. The two most important of these are the formation of fatty alcohols and terminal alkenes from ethylene. These capitalize on the Aufbau reaction for formation of alkyl chains that can reach to C200, but the commercially important alkyls are those from C14 to C20 Oxidation of the aluminum alkyl followed by acidic hydrolysis yields predominately C14 to C20 alcohols and alumina (equation 36). The alcohols are converted to... 

Yamamoto and Maruoka investigated the reaction of chiral acetals with organoaluminum reagents. Unprecedented regio- and stereochemical control was observed in the addition of trialkylaluminums to chiral a,/3-unsaturated acetals derived from optically pure tartaric acid diamide [83]. The course of the reaction seemed to be highly influenced by the nature of substrates, solvents, and temperature. These findings provide easy access to optically active a-substituted aldehydes (84), /3-substituted aldehydes (85), a-substituted carboxylic acids (86), or allylic alcohols (87). Because optically pure RJi)- and (5,5)-tartaric acid diamides are both readily available, this method enables the predictable synthesis of both enantiomers of substituted aldehydes, carboxylic acids, and allylic alcohols from a,/3-unsaturated aldehydes (Sch. 54). 

Yamamoto et al. recently reported that the exceptionally bulky organoaluminum reagents MAD and MABR, which had been developed for selective transformations and as Lewis acid-type receptors with molecular recognition capacity, seemed to have... 

REACTIONS OF ORGANOALUMINUM REAGENTS WITH ACID DERIVATIVES... 

Lewis acid, This organoaluminum reagent (MeA10) , a partial hydrolysis product of trimethylaluminum, is more efficient than conventional Lewis acids such as MCjAl, as catalyst for inducing Diels-Alder reactions and aminolysis of esters. 

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