JS-Diketones

Finally, 4-aminopyrimidine-5-carbaldehydes with cyclic jS-diketones, such as cyclo-hexane-l,3-dione, give partially reduced pyrimido[4,5-f>]quinolones (239) (76JOC1058). 

Mixed Claisen-like reactions can also be carried out between an ester and a ketone, resulting in the synthesis of a jS-diketone. The reaction works best when the ester component has no a hydrogens and thus can t act as the nucleophilic donor. For example, ethyl formate gives high yields in mixed Claisen condensations with ketones. 

Problem 23.22 How would you prepare the following compound using a Robinson annulation reaction between a jS-diketone and an, /3-unsaturated ketone Draw the structures of both reactants and the intermediate Michael addition product. 

There are also reactions in which electrophilic radicals react with relatively nucleophilic alkenes. These reactions are exemplified by a group of procedures in which a radical intermediate is formed by oxidation of readily enolizable compounds. This reaction was initially developed for /3-ketoacids,311 and the method has been extended to jS-diketones, malonic acids, and cyanoacetic acid.312 The radicals formed by the addition step are rapidly oxidized to cations, which give rise to the final product by intramolecular capture of a carboxylate group. 

More advanced semiempirical molecular orbital methods have also been used in this respect in modeling, e.g., the structure of a diphosphonium extractant in the gas phase, and then the percentage extraction of zinc ion-pair complexes was correlated with the calculated energy of association of the ion pairs [29]. Semiempirical SCF calculations, used to study structure, conformational changes and hydration of hydroxyoximes as extractants of copper, appeared helpful in interpreting their interfacial activity and the rate of extraction [30]. Similar (PM3, ZINDO) methods were also used to model the structure of some commercial extractants (pyridine dicarboxylates, pyridyloctanoates, jS-diketones, hydroxyoximes), as well as the effects of their hydration and association with modifiers (alcohols, )S-diketones) on their thermodynamic and interfacial activity [31 33]. In addition, the structure of copper complexes with these extractants was calculated [32]. 

Four different products (38-41) are involved in the reaction of jS-diketones and pyrroledicarboxaldehyde 37 [Scheme 10 89H(29)273]. Regarding a,iS-unsaturated ketones 41, it seems that the cleavage of... 

Alkali metals may also form stable complexes for which parent ions are observed in the mass spectra species such as NaHo(C8Hjo02F3)4+ (m/e = 968) (108) and metal jS-diketones (109) have been observed. In the latter case, the 1 1 complexes have spectra complicated by polymeric... 

Recent studies have involved some fluorinated monothio-jS-diketones with zinc and nickel (195) and palladium and platinum (196). Both nickel and zinc show valence change of the metal. 

Alternative furan ring fusion involves the reactions of phenyliodonium ylides of cyclic seven-membered jS-diketones with alkynes. These processes lead under mild conditions to cyclization products 152. The high regioselectivity can be explained by the formation of dipolar intermediate 151 favored by the predominant enolization of the carbonyl adjacent to phenyl ring. Terminal alkynes react in the similar fashion, although, in this case, mixtures of regioisomers have been reported due to steric hindrance in the intermediate enol (Scheme 30 (1993JOC4885)). 

Nach dem gleichen Chemismus verlauft die Kondensation eines Fettsaureesters bzw. Carbonsaureesters mit einem Keton zu einem jS-Diketon, wobei das Keton als Methylenkomponente reagiert. 

Up to now no reversible photorearrangement of a nonenolizable jS-diketone to an endocyclic enol lactone is known, but several examples of photo-stationary equilibria between j8-diketones and exocyclic enol lactones have been established. After irradiation of either 175 or 176 in benzene a photoequilibrium mixture containing 175 + 176 + 177 is formed with a product ratio 3 95 2.109 With 2-mono- or disubstituted 1.3-indanediones and cis- and frans-alkylidenenaphthalides 43 44,16 it was shown that the ratio of enol... 

Thompson, D. W. Structure and Bonding in Inorganic Derivatives of jS-Diketones. Vol. 9,... 

The Cotton effects in mixed amino acidate/acetylacetonate complexes [Cr(acac)2L] (L = l-alanine, L-valine or L-phenylalanine) have been studied 774 absolute configurations were assigned by reference to the parent tris(acetylacetonate) complexes. Synthesis was achieved by the photolysis of mixtures of the amino acid and [Cr(acac)3]. The partial photoresolution of both cis- and irans-(l,l,l-trifluoro-2,4-pentanedionato)chromium has been accomplished by irradiation with circularly polarized light (5461 A) in chlorobenzene solution.775 The results indicated that both bond rupture and twist mechanisms were important. A number of other jS-diketonates have also been investigated.776... 

There has been some work on interactions between LSRs and transition metal complexes, both NMR shifts and relaxation rates being studied. Presumably the mode of interaction is by means of bridges formed by the donor atoms of one complex which bond in a labile manner to the metal ion of the second complex. Interactions examined include those between [Eu(fod-d[Pg.1104]

Zinc chelates of the stoichiometry Z11L2 have been prepared from various substituted monothio-jS-diketones RC(SH)=CHCOCF3(HL).756 The mass spectra of Znl complexes of the monothio-/ -diketones RC(SH)=CHCOPh (R = Me or Ph) have been reported.757 The most interesting feature is the loss of H2S, which does not occur with the free ligands, or with metal complexes of fhiorinated /3-ketones.758... 

The methine proton in the keto form and the hydroxyl proton in the enol form of jS-diketones are acidic and their removal generates 1,3-diketonate anions (2), which are the source of an extremely broad class of coordination compounds referred to generically as diketonates or acetylacetonates. The synthesis, structure and properties of these compounds form the focus of this chapter. Di-ketonate anions are powerful chelating species and form complexes with virtually every transition and main group element. The scope of this chemistry is very large and it has been assessed earlier in several excellent reviews.9-14... 

The lanthanide elements, in their complexes with jS-diketones, tend to adopt interesting, higher coordination geometries. These compounds frequently crystallize as hydrates from which water removal without decomposition of the compound is difficult. Some structural information is summarized in Table 1. 2,2,6,6-Tetramethylheptanedionate chelates of the lighter lanthanides (La to Dy) can be obtained in nonsolvated form, crystallize in the monoclinic system and contain dimer units whereas the heavier analogues (Ho to Lu) tend to be orthorhombic with isolated six-coordinate monomers.128... 

While complexes in which the metal is coordinatively unsaturated frequently oligomerize utilizing bridging jS-diketonate ligands, a different mode of aggregation is believed to occur in M(CO)2-(MeCOCHCOMe) (M = Rh, Ir), The near planarity of the acetylacetonate permits these flat molecules to stack so that short (3.20 A for Ir) metal-metal contacts are formed. This leads to highly anisotropic DC electrical transport properties and these compounds are semiconductors. 

Rare earth chelates derived from alkyl- and fiuoroalkyi-substituted jS-diketones are useful, even as mixtures, as anti-knock additives in gasoline.354,355... 

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