Acetylacetonate derivatives

Very few examples of bridging non-cyclic methanides of gold are known. Among them the complex 79 has been reported as the result of the reaction of phosphine-phosphonium derivatives with acetylacetonate derivatives of gold(I) [103,104]. The complexes 80 [89,98], already seen in previous paragraphs, cor-... 

Other metal complexes also have promising anticancer activity. Two Ti(IV) complexes are on clinical trial, an acetylacetonate derivative (budotitane) and titanocene dichloride, and the antimetastic activity of octahedral Ru(III) complexes is attracting attention, one of which is now on clinical trial. Ru(III), like several other metal ions, can be delivered to cells via the iron transport protein transferrin. 

Acetylacetone derivatives of bis-dithiolobenzoquinone 232 show remarkable reactivity (95M615) with cyanoacetic acid derivatives 27 in ethanol with piperidine. They proceed via symmetrical elimination of two acetyl groups and subsequent cyclization to bis-pyrano derivatives 233 (Scheme 89). 

Zirconium acetylacetonate can react in a similar way and as noted previously, surface analysis of zirconium acetylacetonate derivatives on corona-discharged polypropylene has shown bonding to the surface carboxyl groups [6]. 

Moreover, 3-benzoyl-2,4-pentanedione (215) is obtained when benzoylchloride is employed to the acetylacetone derivate i94143) whereas the reaction with benzaldehyde results a mixture of 3-benzylidene-2,4-pentanedione (213) and 3-[a-hydro-xy-benzyl]-2,4-pentanedione (214)143 ... 

The M4L6 tetrahedral capsule motif was first exploited by Saalfrank and co-workers [14] who produced tetrahedral species from bis(acetylacetonate) derivatives, with binding sites that diverged by 60°, and Mg2+ cations. Salts formed... 

During this study, the authors noted that aging of the catalyst in the absence of substrate resulted in a decrease in the enantioselectivity in the Diels-Alder reaction. Aging the catalyst in the presence of the substrate, however, provided the most enantioselective catalyst. These results suggested that the substrate stabilized the catalyst. The authors then examined the abihty of various substrate-like additives to stabilize the catalyst. It was found that some additives not only stabilized the catalyst, but also impacted the catalyst enantioselectivity. When 3-acetyl-l,3-oxazolidin-2-one was used as additive the endo (25,3f )-product was formed with 93% ee. In contrast, acetylacetone derivatives led to a reversal of the facial selectivity. Using the additive 3-phenylacetylacetone as the additive resulted in formation of the (27 ,3i9)-product in 81% enantioselectivity. In both instances, the configuration of the chiral hgand was the same (f )-BINOL. A similar reversal of enantioselectivity with these additives was observed when other substrates were employed. 

Figure 2.2 Keto-enol tantomerism eqnUibrimn of acetylacetone derivatives.

Several routes to benzaldehydes have been elaborated from 1,3-diketones, a,/f-unsaturated diketones or from polyenes. Thus, acetylacetone derivatives (51) are useful precursors of 2,4-dichlorobenzaldehydes (52) by way of di-formyiation and cyclization.44 The best yields are obtained when R1 is... 

Rhodium(I) acetylacetonate derivatives form allyl complexes when reacted with allene ss- ... 

Diketones exist.in solution as mixtures of keto (la) and enol (lb) forms, related by a 1,3 hydrogen shift. Keto-enol equilibria have been measured by NMR techniques and the residence time for hydrogen atoms in the two-weU potentials of unsymmetrical O—H O hydrogen bonds in unsymmetrically substituted acetylacetone derivatives has been obtained from NMR spectra. ... 

By far the most frequently occurring acetylacetonate derivatives are those in which the enolate anion is coordinated to a central metal atom through both oxygen atoms. A classic example of this is the well-known tris(acetylacetonato)iron(III) complex (Fig. IB) whose structure has been determined by single crystal X-ray structure analysis (7). Crystallographic data show that the two chelate ring C—C bond distances are... 

Exemplificative of a third type of oxygen-bonded acetylacetonate derivative is the compound formed from the reaction trimethylchloro-silane and acetylacetone (77). The product from this reaction is 2-tri-methylsiloxy-2-pentene-4-one. It is to be noticed that this silicon compound contains a dangling ligand even though several chelated acetyl-acetonates of silicon are known. Dangling complexation of potential... 

Far less numerous than oxygen-chelated acetylacetonate derivatives are those in which the metal atom is bonded directly to the unique (J) carbon atom rather than to the enolate oxygens. Although metal complexes of this t5q>e have all been characterized recently (since 1962), the first carbon-bonded acetylacetonate complex, potassium chlorobis(acetyl-acetonato)platinate(II),... 

The third and final class of acetylacetonate derivatives to be discussed are those containing bridging enolate ligands giving rise to oligomeric or... 

Experimental The three catalyst precursors were synthesized using Pt- and Ru-chlorides as the starting material for the co-reduction with N(oct)4Bet3H (Cat.1), LiBet3H (Cat2), respectively and the acetylacetonate derivatives for Al(me)3 coreduction (Cat 3). The as-prepared colloidal catalyst precursors were supported on Vulcan XC72, as exempUfied for (Cat 1) in Fig. 2.21, and activated via conditioning at 300°C (cf Section 2.4.2.1). 

The methyl carbons in H(acac), Be(acac)a, and Al(acac)s move upfield on substituting Cl at the 3-position, while the methyl protons are shifted down-field. The carbonyl carbon resonances for 3-substituted acetylacetonate derivatives, acac-X, increase in the order X = Br[Pg.395]

The enantiomeric purity was determined by conversion into the acetylacetonate derivative COP-acac (see below) and the enantiopurity was shown to be >99% by HPLC piacel Chiralpak AD-H (0.46cm x 25cm) column, withl.Oml/minute flow rate and eluted with 95 5 hexanes wo-PrOH]. The retention time for S-COP-acac is 5.1 minutes whereas that of 7 -COP-acac would have been -3.1 minutes [Anderson, Kirsch and Overman Org Synth 84 148 2007.]... 

The optimum pH for reaction is around 5 for CHD, whereas formaldehyde reacts with dimedone best at about pH 7. CHD and dimedone derivatives have much higher fluorescence quantum yields than those of acetylacetone derivatives [432]. 

---