Structure 3-diketonate//3-diketones

Compounds A and B are isomenc diketones of molecular formula CgHjQ02 The H NMR spectrum of compound A contains two signals both singlets at 8 2 2 (six protons) and 2 8 (four protons) The H NMR spectrum of compound B contains two signals one at 8 1 3 (triplet six protons) and the other at 8 2 8 (quartet four protons) What are the structures of compounds A and B" ... 

Diketones and tetraketones derived from aromatic compounds by conversion of two or four SCH groups into keto groups, with any necessary rearrangement of double bonds to a quinonoid structure, are named by adding the suffix -quinone and any necessary affixes. 

The alkylation reactions of enolate anions of both ketones and esters have been extensively utilized in synthesis. Both very stable enolates, such as those derived from (i-ketoesters, / -diketones, and malonate esters, as well as less stable enolates of monofunctional ketones, esters, nitriles, etc., are reactive. Many aspects of the relationships between reactivity, stereochemistry, and mechanism have been clarified. A starting point for the discussion of these reactions is the structure of the enolates. Because of the delocalized nature of enolates, an electrophile can attack either at oxygen or at carbon. 

Kurath described the conversion of 3a,17y5-diacetoxy-5)9-androstan-12-one (partial structure 78) to diketone (79) by bromination of (78) and hydrolysis of the C-11 epimeric bromo ketones... 

Several carboxylates, both simple salts and complex anions, have been prepared often as a means of precipitating the An ion from solution or, as in the case of simple oxalates, in order to prepare the dioxides by thermal decomposition. In K4[Th(C204)4].4Fl20 the anion is known to have a 10-coordinate, bicapped square antipris-matic structure (Fig. 31.8b). -diketonates are precipitated from aqueous solutions of An and the ligand by addition of alkali, and nearly all are sublimable under vacuum. [An(acac)4], (An = Th, U, Np, Pu) are apparently dimorphic but both structures are based on an 8-coordinate, distorted square antiprism. 

Structure-activity studies of 5,6,7,8-tetrahdyro-5,5,8,8-tetramethyl-2-quinoxaline derivatives necessitated the preparation of thiophene-containing compound 17. Stetter conditions using thiazolium salt 20 as catalyst resulted in the preparation of 1,4-diketone 21 from 18 and 19. Condensation of 21 with phosphorus pentasulfide followed by saponification resulted in 17. In this fashion, the authors replaced the amide linker of parent compound 22 with the rigid thiophene moiety. 

Krohnke observed that phenacylpyridinium betaines could be compared to 3-diketones based on their structure and reactivity, in particular, their ability to undergo Michael additions. Since 3-dicarbonyls are important components in the Hantzsch pyridine synthesis, application of these 3-dicarbonyl surrogates in a synthetic route to pyridine was investigated. Krohnke found that glacial acetic acid and ammonium acetate were the ideal conditions to promote the desired Michael addition. For example, N-phenacylpyridinium bromide 50 cleanly participates in a Michael addition with benzalacetophenone 51 to afford 2,4,6-triphenylpyridine 52 in 90% yield. 

In 1898, Lowry observed that a-nitrocamphor (81) under Nef conditions did not give the expected a-diketone, but instead a compound to which he assigned, with little evidence, the oximino anhydride structure (85). This structure was recently corrected by Larson and Wat to the W-hydroxyimide (84). 

In addition to the intermolecular Paterno-Buchi reaction, the intramolecular variant has also been studied the latter allows for the construction of bicyclic structures in one step. For example the diketone 8 reacts quantitatively to the bicyclic ketone 9 ... 

As we have mentioned previously, 1,3-diketone and anilide were very effective reducing agents for vinyl polymerization initiated by ceric ion, respectively. Acetoacet-anilide (AAA), a compound having a 1,3-diketone and an anilide structure as well ... 

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. 

Diels-Alder reaction of, 575 electrostatic potential map of, 576 evidence for, 575 structure of, 576 Bergman, Torbern, 2 Bergstrom, Sune K., 1068 Beta anomer, 984 Beta-carotene, structure of, 172 industrial synthesis of, 722 UV spectrum of, 504 Beta-diketone, 851... 

Cyclopentenones. from 1.4-diketones. 886-887 Cyclopropane, angle strain in, 115 bent bonds in. 115 from alkenes. 227-229 molecular model of, 111. 115 strain energy of, 114 torsional strain in, 115 Cystathionine, cysteine from. 1177 Cysteine, biosynthesis of, 1177 disulfide bridges from, 1029 structure and properties of, 1018 Cytosine, electrostatic potential map of, 1104... 

Digitoxigenin, structure of, 1097 Digitoxin, structure of, 989 Dihalide, alkynes from, 261 Dihedral angle, 94 Diiodomelhane. Simmons-Smith reaction with, 228-229 Diisobutylaluminum hydride, reaction with esters, 812 structure of, 699 Diisopropylamine, pK.d of, 923 1,3-Diketone, pfCa of, 852 Dimethyl disulfide, bond angles in, 20 structure of, 20 Dimethyl ether, electrostatic... 

The potential of such reaction sequences for the generation of molecular diversity was also demonstrated by the synthesis of a library of heterocycles. Epoxide ring-opening with hydrazine and subsequent condensation with (3-diketones or other bifunctional electrophiles gave rise to a variety of functionalized heterocyclic structures in high purity [34]. A selection based on the substrate derived from cyclohexene oxide is shown in Scheme 12.12. 

Barbituric acid can be considered as a cyclized malonic acid diamide (malonyl-urea). It is therefore a cyclic diketone that may be classified, in the sense of the compounds discussed in Section 12.6, as a coupling component with a methylene group activated by two carbonyl groups in the a- and a -positions. The reaction with arenediazonium salts was studied by Nesynov and Besprozvannaya (1971). These authors obtained coupling products (in good yield) that they considered to be arylhydrazones. Coupling with 4-(phenylazo)benzenediazonium chloride was studied by Chandra and Thosh (1991). The lH NMR spectra of these compounds are consistent with the arylhydrazone structure 12.68. 

Structure and bonding in inorganic derivatives of (l-diketones. D. W. Thompson, Struct. Bonding (Berlin), 1971,9,27-47 (69). 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

Tris(bipyridyl) complexes structure, 1, 63 Tris(diketonate) complexes structure, 1,65 Trisdithiolencs metal complexes synthesis, 2, 597... 

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