Cyclopentane-1,2-diones

The crude product is dissolved m 11. of boiling water, and the solution is filtered quickly through a preheated fritted-disk funnel (Note 7). The filtrate is concentrated on a hot plate at atmospheric pressure to a volume of 550-600 ml. and allowed to stand at 0° overnight. The crystals are collected by filtration and dried at 85° to afford 50 0-50 6 g (70-71%) of 2-methyl- 1,3-cyclopentane-dione, m p. 210-211° (Note 8)... 

Equations 36 and 37 illustrate that y-oxoacids or acetals of y-oxoesters are available under appropriate conditions 62,74). Heating with concentrated hydrochloric acid transforms 110 to the a,fS-unsaturated lactone 111 (Eq. 38)62), whereas compounds displaying the suitable substituent pattern can be cyclized to 1,3-cyclopentane diones with bases (Eq. 39)6I). 

Indolizine-diones, tetronic acids, [l,2]-oxazin-3,5-diones and cyclopentane-diones were obtained with similar cyclization steps. 

Pyrazolines, spirotetramates, cyclohexan-diones, cyclopentane-diones. oxazinane 3,5-diones,... 

High levels of herbicidal activity on grasses were found with many types of diones such as tetramates, cyclopentane-diones, cydohexanediones or oxazin-3,5-diones linked to 2,6-diethyl-4-methyl-benzene. 

The cyclopentane dione (0.154 g 5.58 x 10" mol) in dry ether (5 ml) is added to a vigorously stirred solution of sodium (0.3 g 1.3 x 10 mol) in dry ethanol (10 ml). After cooling to 0°C a solution of 3-methyl-2-butenyl bromide (0.075 g 5.03 x 10 mol) in ether (5 ml) is added. The mixture is stirred for 18 h, diluted with water, acidified (HCI) and extracted with ether. The ethereal layer is separated, washed with water, dried and concentrated in vacuo to an oil. Distillation yields 2-(3-methylbutanoyl)-5-(3-methyl-2-butenyl)-3,4-dihydroxy-4-(4-methyl-3-penten-1-ynyl)-2-cyclopentenone (0.084 g 44%) as a light-yellow oil with a boiling point of 100°C (bath temperature) at 5 X 10" mm Hg. 

The mechanism of the reaction of the vinyl carbinol (2) with cyclic 1,3-diketones has been discussed [1077]. New 1,3-dicarbonyl compounds have been condensed with this carbinol. Thus, the reaction with 2-chloro-l,3-cyclopentanedione led to an analog of 18-norestrone (1) with an aromatic ring C [1078]. The condensation of the isothiouronium salt of the vinyl carbinol (2) (see Scheme 38) with 4-acetoxy-2-methyl-l,3-cyclopentane-dione gave an unstable highly unsaturated compound (3) the catalytic hydrogenation and demethylation of which led to 8-isoestrone with an overall yield of 28% on the (2) [1079]. The reaction of the vinyl carbinol (2) with a, y-dimethyltetronic acid led to compound (4). Treatment with pal-ladized carbon and alkaline hydrolysis gave the keto ester (5) and the electrochemical reduction of this yielded racemic bisdehydrodoisynolic acid (6) [1080]. 

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. 

A general preparation of 2-acetonyl-2,4,6-triaryl-2//-thiopyrans 58 was discovered in the reaction of corresponding 2,4,6-triarylthiopyrylium perchlorates with ethanolic acetone catalyzed with various dialkylammonium salts (86GEP235455, 86JPR573). This preparative procedure was successfully extended to cyclohexane- and cyclopentane- 1,2-diones as the carbonyl components (89JPR853 90GEP280324). The action of bases on thiopyrylium salts may caused their dimerization to thiopyranyl derivatives under suitable conditions (89KGS479). 

Cyclohexene-l,4-dione, 2,3,5-tiichloro-3, 6-bis(l,l-dimethylethyl)- [5-Cyclo-hexcne-1,4-dione, 2,3,5-tnchloio-3,6-dwert-butyl-], 55, 33 Cyclopentadiene, 55, 15,16 Cyclopentane acetyl-,55,25 Cyclopentane 1-cyano-l-phenyl-, 55,94 Cyclopentane methyl-, 55, 62 Cyclopropane, 1-acetyl-l-phenyl-, 55 94... 

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

Cyclohexene TlCl04/HCl04-(Pt) tI(cio4)3 Cyclopentane-1-carboxylic acid, Cyclohexanone, Cyclohexane-1,2-dione, Cyclohexane-1,2-diol 247... 

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

Microbial reduction of prochiral cyclopentane- and cyclohexane-1,3-diones was extensively studied during the 1960 s in connection with steroid total synthesis. Kieslich, Djerassi, and their coworkers reported the reduction of 2,2-dimethylcyclohexane-l,3-dione with Kloeokera magna ATCC 20109, and obtained (S)-3-hydroxy-2,2-dimethylcyclohexanone. We found that the reduction of the 1,3-diketone can also be effected with conventional baker s yeast, and secured the hydroxy ketone of 98-99% ee as determined by an HPLC analysis of the corresponding (S)-a-methoxy-a-trifluoromethylphenylacetate (MTPA ester).(S)-3-Hydroxy-2,2-dimethy1cyc1ohexanone has been proved to be a versatile chiral non-racemic building block in terpene synthesis as shown in Figure 1. 

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... 

Pathways for the biosynthesis of the cyclopentane carotenoids capsanthin [3,3 -dihydroxy- 8,K-caroten-6 -one (146)] and capsorubin [3,3 -dihydroxy-ir,K-caro-tene-6,6 -dione (147)] have been proposed from consideration of the carotenoids identified in extracts of lilies and red peppers. 

Intramolecular [2 + 2] photocycloadditions have been used successfully for the syntheses of (polycyclic) cage compounds. Recent examples of such reactions are the formation of pentacyclo[5.4.0.02 6.031°.05 9]undecane-8,ll-dione-4-spiro-l-cyclopentane,55 hexacy-clo[7.4.2.01,9.03,7.04 14.061s]pentadeca-10,12-diene-2,8-dione-5-spiro-l -cyclopropane,56 pen-tacyclo[5.4.0.02 6.031°.04 8]undecane57 and pentacyclo[6.4.0.02 7.03 12.06 9Jdodeca-4,10-diene.58 Irradiation of benzoquinone tetrahydropentalene adducts afford cage compounds which are easily converted to angular tetraquinanes.59... 

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... 

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... 

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...

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. 

In HC1 solution, in the presence of SnCl2, Mov forms complexes [MoO(Hd)2]+ with the dioximes (H2d) of cyclohexane-1,2-dione and cyclopentane-1,2-dione. Several compounds of tetradentate Schiff bases255,274 with oxomolybdenum(V) have been prepared and the crystal structure of frans-[MoO(salen)(MeOH)]Br has been determined.274 The Mo—O, distance is 1.666(10) A, and there is close interaction in the crystal between each cation and an attendant bromide anion. 

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