Addition of Other Organometallics

Potassium trifluoro(organo)borates such as ArBF3K couple with benzaldehydes to give carbinols using the catalytic combination of Rh(H2C=CH2)2Cl2 and Bu P, in toluene-water mixtures at 60 °C.248 The reaction tolerates a wide range of functionality and works well for hindered benzaldehydes, and even for aliphatic aldehydes. 

Aldehydes, R CIIO, have been alkylated to give secondary alcohols, R1CH(OH)R2, using boranes, R2B, and a nickel(II) catalyst.250 

Formation of secondary alcohols, RCH(OH)Ar, from aldehydes and arylboronic acids, ArB(OH)2, is catalysed by a range of palladium(O) complexes, but chloroform is required.251 Palladium-chloroform complexes are equally effective, and evidence for (Ph3P)2Pd being converted to palladium(II) intermediates, (Ph3P)2Pd(X)-CHCl2, is presented (X = Cl, then OH). 

An enantioselective addition of trialkylaluminium to aldehydes uses chiral a-hydroxy acids as ligands.252 

Molecular dynamics simulations have been used to predict solvent and temperature effects in the nucleophilic addition of a-chiral carbonyl compounds.253 Prediction of diastereoselectivity break temperatures (i.e. inversion points) has been achieved with fair accuracy by comparison with experimental data on n-BuLi addition. Dramatic differences are seen for additions to 2-phenylpropanol in pentane solvent, compared with octane. 

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Besides 1,3-oxathianes, the 1,3-dithiane 1-oxide moiety can be used for directing the nucleophilic addition of an organometallic reagent to a carbonyl group in a diastereoselective manner. The addition of methylmagnesium iodide to the 2-acyl-l,3-dithiane 1-oxide 23A leads exclusively to the diastereomer which is formed by Re-side attack. On the other hand, addition... 

Nucleophilic addition of zinc organometallic reagents to other C=N bond-containing... 

The stereoselectivity of reduction of carbonyl groups is effected by the same combination of steric and stereoelectronic factors which control the addition of other nucleophiles, such as enolates and organometallic reagents to carbonyl groups. A general discussion of these factors on addition of hydride is given in Section 3.10 of Part A. 

There is three times as much of one of the two diaslereoisomeric products as there is of the other, and the major (anti) diastereoisomer is the one in which the nucleophile has added to the front face of the carbonyl group as drawn here. We can make these same two diastereo isomers by addition of an organometallic to an aldehyde. For example, this Grignard reagent gives three times as much of the syn diastereoisomer as the anli diastereoisomer. The major product has changed, but the product still arises from attack on the front face of the carbonyl as shown. 

The method was made considerably more general by inclusion of a catalytic amount of a palladium(O) complex during addition of the organometallic. Alkenylcopper reagents actually react relatively slowly with acid halides but, in a fashion analogous to other alkenyl metal species (see Section 1.13.4), they may be readily transmetallated to form an acylpalladium(II) complex which then undergoes reductive elimination to the product (Scheme 29)." A further discussion of acylation mediated by palladium complexes is included in Section 1.13.4. Interestingly, a,P-unsaturated acid chlorides react under these conditions to form divinyl ketones. 

Among the other hydride donors [S91], organometallic reagents bearing a C-H bond in the 0-position can be used for reduction of carbonyl compounds. In such reactions, direct addition of the organometallic substituents to the caibonyl group must be avoided. Meerwein-Verley-Pondorf reductions [624b] have also been studied, as have reductions based on models of NADH [625],... 

The largest consumption of sodium worldwide, as of the mid-1990s, is the production of tetraethyllead and tetramethyllead antiknock compounds for gasoline. This production is outside of North America. Sodium is also used for the production of other organometallic compounds such as methylcyclopentadienylmanganese tricarbonyl (MMT), another gasoline additive. 

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