Cyclopentane-l ,2-dione

This route is compatible with various functionality and by choosing the appropriate reagents amino-, halo-, and nitro-substituted furoxans can be prepared illustrative examples include the conversion of cyclopentan-l,2-dione dioxime to the thermally labile trimethylenefuroxan using aqueous sodium hypochlorite <79JCR(S)314>, and of the parent glyoxime to 3,4-dinitrofuroxan by... 

Oxalic esters added in small amounts, with ice-salt cooling, under H2, to Na-ethoxide in ether, then glutaric acid ester added, refluxed 1 hr., the ether distilled off, the mixture heated to 105°, and the resulting Na-compound decomposed in cold 20%-H2SO4 —diethyl cyclopentane-l,2-dione-3,5-dicarboxylate. Y 65 %. (G. Hesse and H. Bucking, A. 563, 31 (1949) f. e. s. G. Hesse and K. W. F. Bockmann, A. 563,37 (1949).)... 

Mean while, to a mixture of 190.0 g 2-bromo-4-fluoro-aniline (1 mol) and 0.6 L water at room temperature was added 3 mol concentrated HCI the resulting thick white slurry was cooled to 0°C. A solution of 1 mol NaN02 in 0.7 L water was added slowly over 25 min, at such a rate as not to exceed an internal temperature of 10°C, and the reaction was aged for 30 min before filtration to remove any insoluble precipitate. This filtered diazonium solution was added to the prepared sodium carboxylate solution at 0°C dropwise over a period of 40 min (Note If added to the solution of sodium carboxylate, then it was not necessary to acidify the sodium carboxylate with concentrated HCI.) The resulting thick yellow slurry was stirred to room temperature, filtered, and dried under a stream of nitrogen to give 270.9 g (4 1 ratio) l-( /Z)-cyclopentane-l,2-dione (2-bromo-4-fluorophenyl)hydrazone as a yellow solid, in a yield of 95%, m.p. 182-187°C. 

To the prepared sodium carboxylate solution at 0°C was added the filtered diazonium solution dropwise over 40 min at a temperature range of 0-4°C. The resulting thick yellow slurry was stirred to room temperature, filtered, and dried under a stream of nitrogen to give 95% (l /Z)-cyclopentane-l,2-dione (2-bromo-4-fluorophenyl) hydrazone, as a yellow solid of steric mixture in 4 1 ratio, m.p. 182-187°C. 

The MBH reactions of non-enolizable a-diketones precursors (Figure 1.4) with the activated olefins, e.g. acrolein, methyl acrylate and acrylonitrile, have been investigated systematically. The reaction of 3,3,5,5-tetramethyl-cyclopentane-l,2-dione (162) with acrolein and acrylonitrile, but not methyl acrylate, afforded the mono-a-hydroxyalkylation products in high yields. Other nonenolizable a-diketones, such as camphorquinone (159), homo-adamantane-2,3-dione (160) and bicyclo[ 3.3.2]decane-9,10-dione (161) reacted only with acrylonitrile, probably due to the hindered nature of the a-dicarbonyl compounds and the difference in steric demand between nitrile and ester. 

Dicarbonyl Compounds.—Ozonolysis of 2-cyclopentylidenecyclopentanone provides a convenient synthesis of cyclopentane-l,2-dione on the ca. 0.4 mole scale.The by-product, cyclopentanone, is recycled via an aldol condensation to regenerate the enone. The method should be applicable to other alicyclic 1,2-diones. Various methods for the preparation of monoprotected 1,2-diones have appeared. Monoacetals of a-dicarbonyl compounds are prepared regio-specifically from enol ethers [equation (32)], following epoxidation in methanol and oxidation of the resulting acyloin acetal. 

Cyclopentane-l,2-dione can be transformed in good yield into its isobutyl mono-enol ether in the same way as the 1,3 dione reaction of the free ketone group with Grignard reagents followed by dehydration of the intermediate carbinol constitutes a general synthesis of 2-alkyl-cyclopentenones... 

In the first of these sequences, often called the Torgov-Smith synthesis, the initial step consists in condensation of a 2-alkyl-cyclopentane-l,3-dione with the allyl alcohol obtained from 6-methoxy-l-tetralone and vinylmagnesium chloride. Although this reaction at first sight resembles a classic SN displacement, the reaction is actually carried out with only a trace of base. 

Pinacol rearrangement driven by the release of the ring strain of a cyclobutane ring has been employed in an extremely efficient manner to form cyclopentanone derivatives. Experimentally. the Lewis acid mediated aldol condensation of benzaldehyde with l,2-bis(trimethyl-siloxy)cyclobutcne at —78 C gave the pinacol 1 in its silylated form.35,36 Subsequent treatment of this pinacol with trifluoroacetic acid at room temperature afforded 2-phenyl-cyclopentane-l,3-dione (2) in 97% yield.35,36... 

Alicyclic 1,2-dionesAn attractive route to cyclopentane-1,2-dione (2) is ozonolysis of 2-cyclopentylidenecyclopentanone (l).2 The main by-product is cyclo-pentanone, which can be recycled to 1. 

The volatiles produced by sugar degradation can make an important contribution to flavour. Pyrolysis of glucose at 300 °C allowed 56 compounds to be identified, the main product being l,4 3,6-dianhydroglucopyranose.567 More than 100 volatiles were separated when glucose was heated at 250 °C for 30 min in air or in nitrogen 4-hydroxy-2-pentenoic acid lactone, 1-(2-furyl)propane-l,2-dione, and 3-methyl-cyclopentane-1,2-dione were identified as new products.568... 

Draw the structural formula of 2-methyl-2-(3-oxobutyl)cyclopentane-l,3-dione and determine the pro chirality centres and the topicities of the hydrogen atoms. 

By condensation of cyclopen tane-l,2-dione with dimethyl 0-ketoglutarate, Weiss and Edwards were able to prepare the [3.3.3]propellanedione 471,1 a molecule in which three cyclopentane rings are conjoined through a common carbon-carbon... 

Alkyl-2-(2-oxopropyl)cyclopentane-l,3-diones 33 were smoothly converted into 2-acetyl-3-alkylcyclohexane-l,4-diones 34 by treatment with sodium hydroxide in water or sodium methoxide in methanol. Ring expansion results from intramolecular aldol reaction followed by ring opening of the bicyclo[3.1.0]hexane system. ... 

Estratriene Series. The Wyeth chemists have published details of their work > > > on the total synthesis of estratriene derivatives prepared mainly for biological evaluation. In addition they described also a new total synthesis of equilin. The Merck group working along similar lines has found that IV is easily prepared from III and can be used to alkylate 2-alkyl-cyclopentane-l,5-diones in cases where III fails. - They also... 

CarbocycUc Steroids.— The Torgov synthesis continues to exhibit its great versatility and was recently employed in the first synthesis of B-homo-oestrone. Condensation of the vinyl alcohol (407) and 2-methy 1-cyclopentane-l,3-dione in the presence of l,4-diazabicyclo[2,2 ]octane and cyclisation with toluene-p-sulphonic acid gave the B-homo-oestrapentaene (409) in 33 % overall yield from 3-methoxybenzosuberone. A three-stage reduction by sodium borohydride, catalytic hydrogenation, and lithium-ammonia afforded 3-methoxy-B-homo-... 

The polyhydrazones of cyclopentane-l,3-diones and -1,2,3-triones, like their cyclohexane counterparts, are accessible from 1,3-diones. For example, cyclopentane- 1,3-dione yields cyclopentane-1,2,3-trione 3-phenylhydrazone... 

D.67) 2-Cyclopenten-l-one, 2-hydroxy-, 2-hydroxycyclopent-2-en-l-one [10493-98-8] 1,2-cyclopentanedione, cyclopentane-1,2-dione [3008-40-0]... 

The Bayer research group described further heterocyclic diones (Fig. 9.5), which all belong to this chemical class 3-aryl-pyrrolidine-2,4-diones 5 [62, 63], 3-aryl-furan-2,4-diones 6 [64], 2 aryl-cyclopentan-l,3-diones 7 [65] 4-phenyl-[l,2]oxazin-3,5-diones 8 [66]. 

The bis-silylated succinoin (10) has been employed to convert an aldehyde or ketone into a 2-substituted cyclopentane-l,3-dione. A spirocyclopentane-1,3-dione can be prepared from a cycloalkanone (Scheme 31). ... 

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