Cyclopentane-l,3-diones

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... 

Die Moglichkeit der Variation sowohl der 1,3-Diketon- als auch der Ole-fin-Komponente macht auch hier die Cycloaddition zu einem wichtigen synthetischen Hilfsmittel. So eroffnet das Additionsprodukt des Enol-acetats des Cyclopentan-l,3-dions an Cyclopenten (Formel 83) (150)... 

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. 

Nucleophilic displacement of fluorine atoms in the reactive allylic position affords an enol of a fluorinated 1,3-diketone, 2H-pentafluoro-cyclopentane-l,3-dione (compound H) [57]. ... 

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. ... 

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... 

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). ... 

A soln. of LiAlH4 in anhydrous tetrahydrofuran treated dropwise at ca. -10° with BFg-etherate, then a soln. of m-methoxystyrene in tetrahydrofuran added, stirred ca. 1 hr. at room temp, under argon, a soln. of 2-methyl-2-(2-diloro-3-keto-4-diazobutyl)cyclopentane-l,3-dione in dry benzene added dropwise, allowed to stand 3 hrs., the soln. of the resulting intermediate in benzene treated with tert-butyl hydroperoxide, the crude 3 -methoxy-ll)5-diloro-14j5-hydroxy-9,10-seco-... 

Several other types of more specialized carbonyl compounds were applied in the cyclization with 2-haloanilines as well. Cyclohexane-1,3-dione, cyclopentane-l,3-dione, indole-3-butanal, cyclopenta[6]indol-l-ones... 

The synthesis began with cyclopentan-l,3-dione 75. A Robinson annela-tion gave 77 via intermediate trione 76. Reduction of the more electrophilic of the two ketones gave 78, which was protected as tetrahydropyranyl ether 79. Deconjugative alkylation of 79 gave 80. Hydrolysis of the THP protecting group and reduction of the ketone (pseudo-axial delivery of hydride) provided 81/82. 

Isopropenyl acetate added with stirring to a suspension of succinic anhydride and anhydrous AlGlg in 1,2-dichlorethane, and refluxed 15 min. 2-acetyl-cyclopentane-l,3-dione. Y 50-55%. F. e. s. F. Merenyi and M. Nilsson, Acta Ghem. Scand. 17, 1801 (1963). 

ICHAIIENCEI Treatment of cyclopentane-l,3-dione with iodo-methane in the presence of base leads mainly to a mixture of three products. 

Cyclopentane-l,3-dione is a valuable intermediate in synthesis. Lick and Schank have shown that the dione can be obtained from norbornene in 70% overall yield according to Scheme 10. The intramolecular oxidative coupling of dilithium enolates of substituted pentane-2,4-diones [i.e. (65)], using Cu(OTf)2, also provides a useful route to cycIopentane-l,3-diones. Gedge and Patten-den have found that rearrangement of 4-ylidenebutenolides with NaOMe in... 

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