0-Diketones dicarboxylic acid ester

Cyclic 2-acyl-j -diketones from dicarboxylic acid esters... 

Reaction of a-diketones with lead tetraacetate Dicarboxylic acid esters from cyclic a-diketones... 

This reaction consists of the condensation of two molecular equivalents of a 1,3 diketone (or a J3-keto-ester) with one equivalent of an aldehyde and one of ammonia. Thus the interaction of ethyl acetoacetate and acetaldehyde and ammonia affords the 1,4-dihy dro-pyridine derivative (1), which when boiled with dilute nitric acid readily undergoes dehydrogenation and aromatisation" to gb e the diethyl ester of collidine (or 2,4,6-trimethyl-pyridine-3,5 dicarboxylic acid (II)). For the initial condensation the solid aldehyde-ammonia can conveniently be used in place of the separate reagents. 

Diethyl 4-hydroxyisoxazole-3,5-dicarboxylate (334) was prepared by the reaction of acetonedicarboxylic acid ester with nitrosyl chloride (78JHC1519). Other 4-hydroxyisoxazoles have been prepared by the reaction of 2-hydroxy (or acetoxy)-1,3-diketones with hydroxylamine (34JA2190, 62HC(i7)i, p. 149), and by hydrolysis of 4-isoxazolediazonium salts (62HC(17)1, p. 149). The parent 4-hydroxyisoxazole has not yet been reported. 

The first in this series to be reported was 4-oxoisoxazoline-3,5-dicarboxylic acid diethyl ester, which was formed by the reaction of nitrous acid on diethyl acetonedicarboxylate in 1891. Quilico described a number of syntheses in his 1962 review and the most general include the reaction of hydroxylamine and a-hydroxy-(or acetoxy)- 3-diketones and the conversion of 4-isoxazolediazonium salts to the hydroxy moiety (62HC(17)1, p. 3). Additional syntheses reported were the oxygenation of a 4-boric acid derivative (67JOM(9)l9) and peroxide oxidation of a 4-nitro-2-isoxazoline (Scheme 151) (79ZOR2436). 

The Hinsberg synthesis of thiophene derivatives describes the original condensation of diethyl thiodiglycolate and a-diketones under basic conditions which provides 3,4-disubstituted-thiophene-2,5-dicarboxylic acids upon hydrolysis of the crude ester product with aqueous acid. ... 

Several examples of conjugate addition of carbanions carried out under aprotic conditions are given in Scheme 2.24. The reactions are typically quenched by addition of a proton source to neutralize the enolate. It is also possible to trap the adduct by silylation or, as we will see in Section 2.6.2, to carry out a tandem alkylation. Lithium enolates preformed by reaction with LDA in THF react with enones to give 1,4-diketones (Entries 1 and 2). Entries 3 and 4 involve addition of ester enolates to enones. The reaction in Entry 3 gives the 1,2-addition product at —78°C but isomerizes to the 1,4-product at 25° C. Esters of 1,5-dicarboxylic acids are obtained by addition of ester enolates to a,(3-unsaturated esters (Entry 5). Entries 6 to 8 show cases of... 

Conjugate addition can also be carried out by completely forming the nucleophilic enolate under kinetic conditions. Ketone enolates formed by reaction with LDA in THF react with enones to give 1,5-diketones (entries 1 and 2, Scheme 1.12). Esters of 1,5-dicarboxylic acids are obtained by addition of ester enolates to a,/J-unsaturated esters (entry 5, Scheme 1.12). 

Among many classes of organic compounds the best results were obtained with the following combination a dihydrojg -dicarboxylic acid as modifier and a fteto-ketocarboxylic acid ester (or Z>era-diketone) as substrate. 

This reaction was initially reported by Franchimont in 1872. It is a condensation of two a-bromocarboxylic acids in absolute alcohol in the presence of sodium cyanide to give 1,2-dicarboxylic acids after hydrolysis and decarboxylation. In the case of a-bromoketones, 1,4-diketones are produced similarly after hydrolysis with phosphoric acid. It was found that the bulky group at the ester end prevents condensation, as in the case of phenyl and naphthyl esters. Although the substituent at j0-position does not prevent such condensation, it reduces the overall yield. In addition, a compound with two ester groups at proper position will form cyclic diacid under such reaction conditions and cyclobutane, " cyclopentane and cyclohexane dicarboxylic acid have been prepared in such a way. In the case of l,4-dibromo-l,4-dibenzoylbutane, a derivative of cyclopentanone is produced after acidic hydrolysis. It should be pointed out that other common solvents—including acetone, ether, and acetonitrile- are not good for this reaction. ... 

Hyperflorin, an antibiotic isolated from St. John s wort Hypericum perforatum L.), has been found on the basis of chemical and spectroscopic evidence to possess structure (639). ° A review on the conformational analysis of bicyclo[3,3,l]nonanes has appeared,and the conformations of l,5-disubstituted-3,7-dimethyIenebicyclo-[3,3,l]nonane derivatives have been shown, on the basis of lanthanide-induced n.m.r. shifts, to be predominantly in the double-chair form. In a notable paper that contains a wealth of information pertinent to adamantane synthesis, it has been reported that bicyclo[3,3,l]nonane-3,7-dicarboxylic acid, its dimethyl ester, and various derivatives exist mainly in the chair-boat conformation. The synthetic entry to these systems is illustrated for the above diester (643) in which the starting point is adamantanone (640) thus, ring expansion with diazomethane followed by SeOj oxidation gave the a-diketone (641) which was cleaved with periodate to give the diacid (642). Esterification using diazomethane gave (643) which exists, as does the diacid, as... 

Another dicarboxylic peroxy acid, peroxyphthalic acid, is used for the Baeyer-Villiger reaction of p-diketones and a-keto esters [334]. Besides peroxy acids, ceric ammonium nitrate oxidizes 2-adamantanone to 2-oxa-homoadamantanone in aqueous acetonitrile in 73% yield at 60 °C after 3 h [422]. Tetracyclone (2,3,4,5-tetraphenyl-2,4-cyclopentadien-l-one) is oxidized by ceric ammonium nitrate in aqueous acetonitrile to tetraphenyl-2-pyrone in 77% yield [422]. 

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