Cyclopentanecarboxylic acid

Especially sensitive towards acid is the ketodiazirine (200). It decomposes on contact with O.IN acid, forming methylenecyclopentanone (213) and cyclopentanecarboxylic acid (214). The products may be formed from a developing vinyl cation (212) by C—C bond shift either to the double bond (213) or across the double bond (214) (B-67MI50800). 

A 250-ml flask is charged with 28 g (0.20 mole) of 2-acetyIcyclohexanone and 25 g (0.22 mole) of 30% hydrogen peroxide in 100 ml of /-butyl alcohol. The solution is refluxed for 3 hours, cooled, and a pinch of palladium on charcoal (10%) is cautiously added. The mixture is refluxed for an additional hour to decompose excess peroxide. The cooled mixture is then filtered through celite, and the volume is reduced by removal of /-butyl alcohol and water at reduced pressure. Distillation of the residue affords about 85% of cyclopentanecarboxylic acid, bp 59-6271 rnm, 123727 mm, 215-21671 atm. 

Problem 20.15 Cyclopentanecarboxylic acid and 4-hydroxycyclohexanone have the same formula I (C6H10O2)/ ancl b01- c°htain an -OH and a C=0 group. How could you distinguish i between them by IR spectroscopy ... 

The Fuvorskii reaction involves treatment of an a-bromo ketone with base to yield a ring-contracted product, for example, reaction of 2-bromocyclo-hexanone with aqueous NaOH yields cyclopentanecarboxylic acid. Propose a mechanism. 

Wiberg and Koch 167) also disagreed with Littler s results, and found that the major product (75%) obtained on treatment of cyclohexanone with aqueous thallium(III) perchlorate was cyclopentanecarboxylic acid (XL). 2-Hydroxycyclohexanone was isolated in only 3 % yield unchanged starting material accounted for the remainder of the product. Wiberg and Koch were unable to detect any cyclohexane-1,2-dione in the product mixture, but did prove that 2-hydroxycyclohexanone did not function as the precursor to the ring-contracted acid. From the results obtained from a study of the oxidation of 2,2,6,6-[Pg.196]

The ultimate product of Hg(II) oxidation is cyclohexane-1,2-dione which is probably produced from 2-hydroxycyclohexanone. The oxidation by thallic perchlorate produces cyclopentanecarboxylic acid in 75 % yield this contrasts with the production of 2-acetoxycyclohexanone by thallic acetate . The mechanism favoured for the production of the carboxylic acid is... 

The action of excess cyclopentanecarboxylic acid on a CDCI3 solution of the cyclopentane drum, 1, causes its signal at -485.8 ppm to disappear and gives rise to four other peaks which correspond to formation of the ladder and an intermediate. These NMR experiments have shown that the hydrolysis process given in Equation 3 is reversible, i.e., a drum forms from a ladder composition and, in the presence of excess acid, the drum can be opened up to yield the ladder formulation. 

Because some of the compounds with general structure 316 have noteworthy pharmacological activities, a number of alternative methods have been developed for the synthesis of the 2-substituted and 2,3-disubstituted derivatives 316. 2-Substituted derivatives of 316 cis, n = 1, 2, 3, 4 trans, n = 2, 3, 4) were prepared (77GEP2643384 80AUP507798) from 312-315 with ethyl benzimidates. The attempted ring closure of trans-2-amino-l-cyclopentanecarboxylic acid to rra/w-fused derivatives failed. In this reac-... 

The short Sanofi route to irbesartan (3) is outlined in Scheme 9.6. Dihydroimidazolone 27, which is prepared from the reaction of 1-amino-cyclopentanecarboxylic acid ester (25) with ethyl pentanimidate (26) in the presence of acetic acid in refluxing xylene, is alkylated with biphenylbenzyl bromide 18 in the presence of sodium hydride in DMF to give 28. Finally, the synthesis of irbesartan (3) is completed by the tetrazole formation from reaction of the nitrile group of 28 with tributyltin azide in refluxing xylene. [See Bernhart et al. (1993a, b).]... 

Problem 17.16 Synthesize cyclopentanecarboxylic acid from malonic ester. ... 

CONJUGATE ADDITION/CYCLIZATION OF A CYANOCUPRATE 2-CARB0METH0XY-3-VINYLCYCL0PENTAN0NE (Cyclopentanecarboxylic acid, 2-ethenyl-5-oxo-, methyl ester)... 

These investigators found that the normal acids occurred in much greater abundance than the branched acids. The cyclic acids isolated by Lochte and coworkers (31) include cyclopentanecarboxylic acid, 2-methylcyclopentanecarboxylic acid, 3-methylcyclopentane-carboxylic acid, cyclopentaneacetic acid, 3-methylcyclopentaneacetic acid, 2,3-dimethyl-cyclopentaneacetic acid, 1,2,2-trimethylcyclopentanecarboxylic acid, cyclohexanecarbox-ylic acid, p-methylcyclohexanecarboxylic acid, and the cis and trans forms of 2,2,6-tri-methylcyclohexanecarboxylic acid. In addition, Lochte and coworkers (31) isolated dimethylmaleic anhydride, which has also been isolated by Nenitzescu and coworkers (42). 

Amino-l-cyclopentanecarboxylic acid [52-52-8] M 129.2, m 330°(dec). Crystd from aq EtOH. 

The methyl ester has also been obtained by esterification of cyclopentanecarboxylic acid.8 The acid, in turn, has been prepared by the Favorskii rearrangement,6 7 9-11 by the reaction of cyclopentyl Grignard reagent with carbon dioxide,12 by the carbonylation of cyclopentyl alcohol with nickel carbonyl13 or with formic acid in the presence of sulfuric acid,14 and by the hydrogenation of cyclopentene-1-carboxylic acid prepared from ethyl cyclopentanone-2-carboxylate 15 or from cyclopentanone cyanohydrin.16... 

Cyclohexylmethylpropiolaldehyde diethyl acetal, 39, 60 1,2-Cyclononanedione, 36, 78 Cyclopentadiene, 32, 41 36, 32, 35 Cyclopentanecarboxylic acid, METHYL ESTER, 39, 37 Cyclopentanol, 2-chloro-, irans-,... 

When one attempts E2 reactions with a-halo ketones using strong bases such as alkoxides, an interesting rearrangement pathway may occur called the Favorskii rearrangement. In this reaction, the a-halo ketone is converted to an ester. For example, 2-chlorocyclohexanone is converted to the methyl ester of cyclopentanecarboxylic acid by treatment with sodium methoxide in ether ... 

Another useful route to cyclopentanes is the ring contraction of 2-bromo-cyclohexanones by a Favorskii rearrangement to give cyclopentanecarboxylic acids. If a,fi-dibromoketones are used, ring opening of the intermediate cyclopropanone leads selectively to /J,y-unsaturated carboxylic acids (S.A. Achmad, 1963, 1965 J. Wolinsky, 1965). 

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