Cyclo pentanone

By pyrolysis of dibasic acids or their salts to yield cyclic ketones. The slow distillation of adipic acid with about. 5 per cent, of baryta affords cyclo-pentanone in good yield ... 

Sodium nitromalonaldehyde momo-iiydrate Warning), 46,104 Sodium sand, 46, 8 reaction with 2 carbomethoxy cyclo-pentanone, 45, 8... 

Conway, C.C., Nie, G., Huesain, N.S. and Fiala, E.S. (1991). Comparison of otddative damage to rat liver DNA and RNA by primary nitroalkanes, secondary nitroalkanes, cyclo-pentanone oxime and related compounds. Cancer Res. 51, 3143-3147. 

Scheme 33 illustrates the difference in reactivity between triazolines obtained from cyclohexanone and cyclo-pentanone enamines. Thus, the reactions of azidophosphonates 239 with cyclohexanone enamines produce unstable aminotriazolines 240 that cannot be isolated due to their spontaneous elimination of amines to provide triazoles 241. Contrary to that, triazolines 242, derived from cyclopentanone enamines, are isolated in good yield (76-88%) and cannot be converted to the corresponding triazoles even by thermolysis <1995H(40)543>. Probably, introduction of a double bond between two five-membered rings would involve too much molecular strain. 

An empirical analysis of c.d. data for compounds containing a chiral cyclo-pentanone ring (e.g. ring D in steroids) has led to the proposal that the observed... 

Friederich (Ref 23) prepd expl nitrates from products of reaction between cyclo-pentanone and cyclohexanone... 

Cyclic ketones react faster than the aliphatic ketones in the order cyclo-pentanone > cyclohexanone > higher-membered cyclic ketones. a-Substi-tuted ketones give the less substituted enamines, which in turn could be alkylated to put a substituent on this position of the ketone [51] (Eq. 11). 

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. 

NC(CH2)3CH2Ni(tnic)]+, a facile non radical cyclization to cyclo-pentanone occurs as the hydrolysis reaction proceeds. 

Figure 29. n-rc Absorption of the cyclo-pentanone and cyclopentenone chromo-phores. 

Hydrocarbonylation of 1,4-dienes.3 Hydrocarbonylation of 1,4-pentadiene catalyzed by Co2(CO)8 results in 2-methylcyclopentanone as the only cyclic product. As expected, a gem-dimethyl group at C3 enhances the tendency to form cyclo-pentanones. Thus hydrocarbonylation of the 1,4-diene 1 leads to the tetramethyl-cyclopentanone 2 with a marked preference for the cw-isomer. The reaction has... 

Exercise 16-12 Explain what factors would operate to make the equilibrium constant for cyanohydrin formation 1000 times greater for cyclohexanone than for cyclo-pentanone. Why What would you expect for cyclobutanone relative to cyclopenta-none Why ... 

Ketones. Normal acyclic ketones can be recognised by a strong band at 1720 cm -1 (e.g. see the spectrum of 4-methylpentan-2-one, Fig. 3.28). Branching at the a-carbon atoms results in an increase in the C—CO—C bond angle and this results in a decrease in frequency of absorption from the normal value of 1720 cm -1 to, for example, 1697 cm -1 as in di-t-butylketone. Conversely as the C—CO—C bond angle is decreased the absorption frequency rises, thus cyclo-pentanone and cyclobutanone absorb at 1750 cm-1 and 1775 cm-1 respectively. 

The method is applicable to a wide range of aliphatic and alicyclic (but not aromatic) carbonyl compounds, and is illustrated here by the conversion of cyclo-pentanone into cyclopentyl cyanide (Expt 5.159). 

Diese Konkurrenzreaktion findet auch mit den Enolacetaten des Cyclo-pentanons, Cycloheptanons und Cyclooctanons statt, wahrend tiber-raschenderweise mit Cyclohexanon-enolacetat das erwartete Bicyclo-octanderivat in guter Ausbeute erhalten werden konnte (146, 269). 

The alicyclic ketones have been identified as being important flavor precursors by Flament et al. (15) and more recently by MacLeod and Ames (44), who identified a similar compound (3-methyl-cyclo-pentanone) in heated ground beef. Flament et al. (15) singled out the importance of these compounds, particularly in the presence of alhylpyrazines. Nishimura et al. (41) produced a meaty odor by heating 2-hydroxy-3-methylcyclopent-2-enone with cyclotene and HaS. Two volatile compounds described as having meaty odor were 2-methyl-cyclopentanone and 3-methylcyclopentanone. Thus, cyclotene appears to be a key precursor of "roast beef" flavor. 

While this catalyst provided good yields and ee-values with substrates bearing a heteroatom in the y-position of the acceptor, in some cases - for example with the aliphatic substrate 32 - the catalyst 33 was superior in the formation of the cyclo-pentanones 34 (Scheme 9.9). 

Epoxyglycerides react with ketones in the presence of boron trifluoride to give 1,3-dioxolane derivatives. In this form they were analysed by GC on a column packed with 3% of OV-1 with temperature programming at 4°C/min from 260° C [649]. Cyclo-pentanone was recommended as the most suitable reagent, and acetone, methyl ethyl ketone, methyl isobutyl ketone and others can also be used. 

The synthesis of (+)-estrone methyl ether (36) illustrates the enantioselective construction of a polycyclic target by the use of chiral auxiliary control to establish the first cyclic stereogenic center [14], In this case, the specific design of the naphthyldiazoester 32 directed Rh-mediated intramolecular C-H insertion selectively toward one of the two diastereotopic C-H bonds on the target methylene. The new ternary center so created then biased the formation of the adjacent quaternary center in the course of the alkylation. The chiral skew in the product cyclo-pentanone (35) controlled the relative and absolute course of the intramolecular cycloaddition, to give the steroid (+)-estrone methyl ether (36). 

FIGURE 3. Fluorescence emission and fluorescence excitation spectra of cyclobutanone and cyclo-pentanone. 

Dihydro- E7b/2,353 [Cyclopenta-non-(0-allyl-oxim)/ A], 469 (1,2,3-Triazin + 1-NR2 -cyclopen-ten), 483 (1,2,4-Triazin + Cyclo-pentanon)... 

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