Cyclopentane-1,3-dione

CYCLOOCTENE, 1-NITRO-, 50, 84 CYCLOPENTANECARBOXALDEHYDE, 1-PHENYL-, 51, 24 Cyclopentane-1,3-dione, 52, 4 Cyclopentanones, 54, 32 CYCLOPENTYLAMINE, 1-PHENYL-,... 

Acetylcyclopentane-l,3-dione can be hydrolyzed by aqueous 2M hydrochloric acid (2 days, 100°) to give cyclopentane-1,3-dione in 63% yield. ... 

Cyclopentane-1,3-diones 3 and 4 were prepared via a silver cation induced solvolysis of 2-bro-momethyl-2-hydroxycyclobutanones. This procedure represents a simple pathway to many 4-substituted and 4,5-disubstituled cyclopentane-1,3-diones.33 In particular, the reaction of 2-bromomethyl-2-hydroxy-3,3-dimethylcyclobutanone with silver nitrate gave 4,4-dimethylcy-clopentane-1,3-dione (3a) in 72% yield.33... 

Some selected examples of such a pinacol rearrangement applied in the preparation of cy-clopentanones are shown in Table 2 further examples can be found in refs 35-39. A number of cyclopentenones, 2,2-disubstituted cyclopentane-1,3-diones and 2,2-disubstituted 3-methylenecyclopentanones were synthesized by this method. 

A modification of this method utilizes the direct conversion of l,2-bis(trimethyl-siloxy)cyclobutene in one step to 2,2-disubstituted cyclopentane-1,3-diones. For example, 2-ethyl-2-methylcyclopentane-l,3-dione (3) was obtained in 91% yield from 1.2-bis(trimethyl-siloxy)cyclobutene and butan-2-one 2,2-dimethylpropane-l,3-diyl acetal.41 Further examples... 

Table 3. 2,2-Disubstituted Cyclopentane-1,3-diones by the One-Step Conversion of 1,2-Bis-(trimethylsiloxy)cyclobutcnc with Acetals3...

Treatment of perfluoro(l-methylcyclopent-l-ene) with aqueous potassium hydroxide gives cyclopentenediol 15 and in 1.2-dimethoxyethane yields the cyclopentane-1,3-dione derivative... 

Disubstituted cyclopentane-1,3-diones and cyclohexane-1,3-diones were used as substrates. After formation of the aldol adducts subsequent intramolecular dehydration furnished products of types 94 and 96. The asymmetric intramolecular aldol reaction proceeds with a broad variety of natural amino acids as organocata-lysts. Among these L-proline was usually found to be the most versatile. For example, conversion of the 2,2-disubstituted cyclopentane-1,3-dione 93 in the presence of L-proline gave the desired product 94 in 86.6% yield and with enantioselectivity of 84% ee [97]. This example and a related reaction with a 2,2-disubstituted cyclohexane-1,3-dione 95 are shown in Scheme 6.42. Chiral induction depends... 

Alkyl-l,3-cycloalkanediones.1 These products can be obtained from cyclohexane- or cyclopentane-1,3-diones by conversion to the monodimethylhydrazones... 

The opposite enantiomer of the starting material is selectively isomerized to enol 30 which tautomerizes to cyclopentane-1,3-dione (31). 

By contrast, the catalytic site responsible for the halogenation, hydroxylation, and other (two-electron) oxygenation reactions has been better, although not completely, characterized by X-ray crystallography of CPO complexed with several substrates (such as iodide/bromide and cyclopentane-1,3-dione) and other compounds (such as carbon monoxide, thiocyanate, nitrate, acetate, formate and, in a ternary complex, with dimethylsulfoxide and cyanide) [88, 90]. The above substrates bind at the distal side of heme, and the corresponding structures were also useful to establish the mechanism of Compound I formation as discussed above [90]. 

Typical cyclic diketones such as dimedone, cyclopentane-1,3-dione, cycloheptane-1,3-dione or cyclic 3-oxocarboxylic acid derivatives such as 4-hydroxycoumarin, 4-hydroxyquinolone, 4-hydroxypyrone, 4-hydroxypyridone or tetronic acid are aminocyclopropylated directly. 

Hamer has reported a synthesis of cyclopentane-1,3-diones (277) using silver ion catalysed ring expansion of the cyclobutanones (278) formed on irradiation of the... 

Condensation of the isothiouronium salt, obtained from the vinyl alcohol (413), with 2-methyl-cyclopentane-1,3-dione has led to a series of A-nor-3-oxa-steroids and similar condensation of the thia-analogue (408) with 2-methyl-cyclopentane-1,3-dione afforded the thia-oestrane (410), which was reduced catalytically to a mixture of 14a- and 14/S-H-dihydro-epimers. Reduction of the remaining conjugated 8,9-unsaturation was less easy than in the carbocyclic analogue metal-ammonia afforded thiols, and catalytic reduction was slow and led to a mixture of, presumably, 8a,9a- and 8, 9jS-epimers. The former isomer (416) which has its 9 -H favourably disposed for hydride abstraction with DDQ readily dehydrogenated to the 9(ll)-olefin which, on subsequent catalytic reduction, gave 6-thia-oestrone methyl ether. Condensation of the same thia-... 

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 product in entry 1 of Scheme 2.10 is commonly known as the Wieland-Miescher ketone and is a useful starting material for the preparation of steroids and terpenes. The Robinson annulation to prepare this ketone can be carried out enantioselectively by using the amino acid L-proline to form an enamine intermediate. The -enantiomer of the product is obtained in high enantiomeric excess. This compound and the corresponding product obtained from cyclopentane-1,3-dione are key intermediates in the enantiose-lective synthesis of steroids. ... 

The Michael addition of 2-methyl-cyclopentane 1,3-dione to acrolein in water gave an adduct (Scheme 25) which was used for the synthesis of 13-a-methyl-14a-hydroxysteroid. ... 

Methyl-2-(3 -oxobutyl)-cyclopentane-1,3-dione 1 (1.82 g, 10 mmol) and (S)-(-) proline (1.15 g, 10 mmol) were stirred in MeCN under Ar at 20 C for a period of 6 days. (S)-Proline (1.11 g, 9.65 mmol) was recovered by filtration. After evaporation of the solvent, the residue was dissolved in EtOAc (30 mL) and filtered through silica gel (4 g) by suction, followed by washing the silica gel with EtOAc (60 mL). The combined filtrates gave after evaporation 1.77 g of crude 2 (97%), = +64.0° (c 1.035, CHCI3). 

Dione 3. A mixture of 1-vinyl-6-methoxytetralol 1 (700 mg 3.7 mmol) and 2-methyl-cyclopentane-1,3-dione 2 (420 mg 3.7 mmol) in xylene (4 mL) and t-butyl alcohol (2 mL) was refluxed with stirring and under N2 for 90 min. Et20 was added and 2 was removed by filtration (115 mg). The filtrate after washing (water, 5% NaHCOs, brine) and drying (MgS04) was concentrated. The residue after recrystallization from MeOH gave 575 mg of 3 (70%) from two crops, mp 76-78 C. 

Of industrial importance in steroid synthesis, the asymmetric reduction of 2,2-disubstituted cyclopentane-1,3-diones such as (89) has been investigated in detail.t ]... 

In a sequential multicatalysis process (organocatalysis/BROENSTED catalysis), saUcy-laldehyde (X), and cyclopentane-1,3-dione (Y) were reacted according to the following sequence ... 

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