Aryl diketone

This procedure represents a novel, convenient, and fairly general method for preparing y-aryl- -diketones. By this method the submitters have phenylated the dianion of 1-phenyl-1,3-butanedione (61%), 2,4-heptanedione (98%), 2,4-nonanedione (78%), 2,4-tridecanedione (53%), and 3,5-heptanedione (50%). Substituted diaryliodonium salts have also been used to produce l-(4-chlorophenyl)-2,4-pentadione (44%), 4-(4-methyl-phenyl)-l-phenyl-l,3-butanedione (44%), and l-(4-methyl-phenyl)-2,4-nonanedione (21%). Under these conditions no more than a trace, if any, of arylation at the a-position of the )3-diketones was observed by gas chromatography analysis. 

Attempts to form the aryl diketone products from higher perfluoro-alkylene ether dicarboxylic acids by the acylation or Grignard reactions, however, were relatively unsuccessful. 

Diphenylisoindole can be conveniently prepared from o-dibenzoyl benzene, for example, by treatment with ammonium formate (Leuckart reaction).5,33 The same type of reaction is observed when the aryl diketone... 

This approach has also been utilised in an enantioselective approach to generate axially chiral diaryl phenols using bmcine as the enatiomerically pure amine base at low temperatures of -20 to -40 °C [87]. The phenols could be obtained in up to 83 % ee. Aryllead triacetates can also be used to arylate [)-diketones. Both linear and cyclic P-diketones with an a-substituent already present could be successfully arylated with a variety of aryllead triacetates. The P-diketone 2-methylcyclohexane-l,3-dione... 

Bisperfluoroalkyl Aryl Diketones. The importance of Cs-symmetric chiral auxdiaries (25), iiK luding diols as the chiml director in asymmetric synthesis persuaded us to undergo a systematic study of the convenient synthesis of such compounds by... 

The synthesis will therefore normally produce a 2,4-substituted pyrrole, with in addition an ester group or an acyl group at the 3-position, if a keto ster or a diketone respectively has been employed, and an ester group or an alkyl (aryl) group at the 5-position, according to the nature of the amino-ketone. 

Dilute sodium hydroxide solution. Carboxylic acids (RCOOH), sulphonic acids (RSO3H), phenols (ArOH), thiophenols (ArSH), mer-captans (RSH), imides (RCONHCOR), aryl sulphonamides (AxSOjNHj), arylsulphonyl derivatives of primary amines (AxSOjNHR), oximes (RCH=NOH), primary and secondary nitro compounds (RCH=NOOH and RjC=NOOH-oci forms), and some enols (e.g., of 1 3-diketones... 

The carbonylation of aryl iodides in the presence of alkyl iodides and Zn Cu couple affords aryl alkyl ketones via the formation of alkylzinc species from alkyl iodides followed by transmetallation and reductive elimination[380]. The Pd-catalyzed carbonylation of the diaryliodonium salts 516 under mild conditions in the presence of Zn affords ketones 517 via phenylzinc. The a-diketone 518 is formed as a byproduct[381],... 

No intennolecular reaction of malonate or /3-keto esters with halides has been reported, but the intramolecular reaction of /3-diketones such as 790 and malonates proceeds smoothly[652,653]. Even the simple ketone 791 can be arylated or alkenylated intramolecularly. In this reaction, slow addition of a base is important to prevent alkyne formation from the vinyl iodide by elim-ination[654]. 

In these types of 1,3-dipolar cycloaddition only one of two possible isomers is obtained and the pyrazole functions have different orientations by the two methods. Another classical synthesis of pyrazoles (Section 4.04.3.2.l(ii)), the reaction between hydrazines and )3-diketones, has been used with success to prepare high molecular weight polypyrazoles (Scheme 65) (81MI40400). A-Arylation (Section 4.04.2.1.3(ix)) of 4,4 -dipyrazolyl with 1,4-diiodobenzene also yields polymeric pyrazoles (69RRC1263). 

The reaction of appropriate 1,3-diketones (302) with hydroxylamine hydrochloride in pyridine (79MI41601) has been reported to result in a regiospecific synthesis of 3-alkyl-5-arylisoxazoles, as has the reaction of an a -bromoenone (307) with hydroxylamine hydrochloride in ethanol in the presence of potassium carbonate (81H(16)145). Regiospecific syntheses of 5-alkyl-3-phenylisoxazoles also result from the reaction of an a-bromoenone (307) with hydroxylamine in the presence of sodium ethoxide (81H(16)145). 3-Aryl-5-methylisoxazoles were prepared from phosphonium salts (304) and hydroxylamine (80CB2852). 

Sanofi-Synthelabo researchers discovered pyrazole 53 and analogs to have potent Cannabinoid receptor-1 (CB-1) antagonist/inverse agonist activity and have progressed 53 into development for treatment of obesity and alcohol dependence. The synthesis of 53 was accomplished by heating the diketone sodium salt 51 with the aryl hydrazine hydrochloride in acetic acid to provide the intermediate 52, which was further derivatized... 

Substrates can be 1,2-diketones with aryl groups as well as some aliphatic substituents, cyclic and heterocyclic diketones. However the benzilic acid rearrangement is of limited preparative importance. 

In this example, the /3-diketone 2-methyJ-l,3-cyclopentanedione is used to generate the enolate ion required for Michael reaction and an aryl-substituted a,/3-unsaturated ketone is used as the acceptor. Base-catalyzed Michael reaction between the two partners yields an intermediate triketone, which then cyclizes in an intramolecular aldol condensation to give a Robinson annulation product. Several further transformations are required to complete the synthesis of estrone. 

The condensation of dihydrazones of aryl-substituted 1,2-diketones with aryl-substituted 1,2-diketones has also been described, albeit with rather low yields (up to 15 %).20 Subsequently, it was explicitly shown that this reaction leads to the same products as the dimerization of benzil monohydrazones, i.e. the 1,2,5,6-tetrazocine system, is not produced, rather the bicyclic tetraazapentalene system is obtained,21... 

Wahrend Aryl-1,2-diketone in der Regel zu a-Hydroxy-ketonen reduziert werden, erhalt man aus Alkan-l,2-dionen auch die entsprechenden Glykole z. B. ... 

A number of microwave-assisted multicomponent methods for the synthesis of imidazoles have been reported [68-71 ]. The irradiation of a 1,2-diketone and aldehyde with ammonium acetate in acetic acid for 5 min at 180 °C in a single-mode reactor provides alkyl-, aryl-, and heteroaryl-substituted imidazoles 39 in excellent yield (Scheme 14) and this method has been used for the rapid and efficient preparation of two biologically active imidazoles, lepidiline B and trifenagrel [68]. 

In the case of a diketone (e.g., 3-tosyloxypentane-2,4-dione), the formation of 5-acetyl-4-methyl-2-aryl-l,3-thiazole derivatives can be realized in very good yields (86-89%) (Scheme 7). All these experiments where performed in a Sears Kenmore unmodified household microwave oven (990 W) equipped with a turntable. The average bulk temperature was estimated by inserting a thermometer in the alumina bath housing the reaction vessel. 

Ordinary ketones are generally much more difficult to cleave than trihalo ketones or p-diketones, because the carbanion intermediates in these cases are more stable than simple carbanions. However, nonenolizable ketones can be cleaved by treatment with a 10 3 mixture of t-BuOK—H2O in an aprotic solvent such as ether, dimethyl sulfoxide, 1,2-dimethoxyethane (glyme), and so on, or with sohd t-BuOK in the absence of a solvent. When the reaction is applied to monosubstituted diaryl ketones, that aryl group preferentially cleaves that comes off as the more stable carbanion, except that aryl groups substituted in the ortho position are more readily cleaved than otherwise because of the steric effect (relief of stain). In certain cases, cyclic ketones can be cleaved by base treatment, even if they are enolizable. " OS VI, 625. See also OS VH, 297. 

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