Cyclopentene-3-carboxylic acid

B. 3-Cyclopentene-1 -carboxylic acid. A 250-mL, one-necked, round-bottomed flask is charged with 35.8 g of 3-cyclopentene-1,1-dicarboxylic acid and then fitted with a reflux condenser capped with a rubber septum and connected to a Nujol-filled bubbler by means of a syringe needle. The contents of the flask are heated in an oil bath at 170-175°C until carbon dioxide evolution is complete (ca. 2 hr) and then allowed to cool to room temperature. The resulting oil is transferred to a 50-mL flask and vacuum distilled without fractionation to provide 23.0 g (89% or 82% overall from dimethyl malonate) of 3-cyclopentene-1-carboxylic acid as a clear, colorless oil, bp 88°C (2 mm) (Note 7). 

The preparation described here of 3-cyclopentene-1-carboxylic acid from dimethyl malonate and cis-1,4-dichloro-2-butene is an optimized version of a method reported earlier3 for obtaining this often used and versatile building block.6 The procedure is simple and efficient and requires only standard laboratory equipment. 3-Cyclopentene-1-carboxylic acid has previously been prepared through reaction of diethyl malonate with cis-1,4-dichloro(or dibromo)-2-butene in the presence of ethanolic sodium ethoxide, followed by hydrolysis of the isolated diethyl 3-cyclopentene-1,1-dicarboxylate intermediate, fractional recrystallization of the resultant diacid to remove the unwanted vinylcyclopropyl isomer, and finally decarboxylation.2>7 Alternatively, this compound can be obtained from the vinylcyclopropyl isomer (prepared from diethyl malonate and trans-1,4-dichloro-2-butene)8 or from cyclopentadiene9 or cyclopentene.10 In comparison with the present procedure, however, all these methods suffer from poor selectivity, low yields, length, or need of special equipment or reagents, if not a combination of these drawbacks. 

Jean-Pierre Depr6s and Andrew E. Greene 195 3-CYCLOPENTENE-1 -CARBOXYLIC ACID... 

C6H802 3-cyclopentene-1-carboxylic acid 7686-77-3 444.11 38.541 2 7511 C6H9CISn chloro(trivinyl)stannane 10008-90-9 419.15 36.173 1,2... 

Methyl 3-cyclopentene-1-carboxylate 3-Cyclopentene-1-carboxylic acid, methyl ester (58101-60-3), 75, 197... 

CYCLOPENTENE-1-CARBOXYLIC ACID (7686-77-3), 75, 195 3-Cyclopentene-1,1-dicarboxylic acid (88326-51-6), 75, 195 Cyclopropanations, enantioselective, 76, 97... 

Cyclopentene derivatives with carboxylic acid side-chains can be stereoselectively hydroxy-lated by the iodolactonization procedure (E.J. Corey, 1969, 1970). To the trisubstituted cyclopentene described on p. 210 a large iodine cation is added stereoselectively to the less hindered -side of the 9,10 double bond. Lactone formation occurs on the intermediate iod-onium ion specifically at C-9ot. Later the iodine is reductively removed with tri-n-butyltin hydride. The cyclopentane ring now bears all oxygen and carbon substituents in the right stereochemistry, and the carbon chains can be built starting from the C-8 and C-12 substit""" ... 

The cyclononadiene in (4.72) is obtained by thermal rearrangement of the photoadduct of a cyclobutene carboxylic acid ester and cyclopentene 484). 

Volume 75 concludes with six procedures for the preparation of valuable building blocks. The first, 6,7-DIHYDROCYCLOPENTA-l,3-DIOXIN-5(4H)-ONE, serves as an effective /3-keto vinyl cation equivalent when subjected to reductive and alkylative 1,3-carbonyl transpositions. 3-CYCLOPENTENE-l-CARBOXYLIC ACID, the second procedure in this series, is prepared via the reaction of dimethyl malonate and cis-l,4-dichloro-2-butene, followed by hydrolysis and decarboxylation. The use of tetrahaloarenes as diaryne equivalents for the potential construction of molecular belts, collars, and strips is demonstrated with the preparation of anti- and syn-l,4,5,8-TETRAHYDROANTHRACENE 1,4 5,8-DIEPOXIDES. Also of potential interest to the organic materials community is 8,8-DICYANOHEPTAFULVENE, prepared by the condensation of cycloheptatrienylium tetrafluoroborate with bromomalononitrile. The preparation of 2-PHENYL-l-PYRROLINE, an important heterocycle for the synthesis of a variety of alkaloids and pyrroloisoquinoline antidepressants, illustrates the utility of the inexpensive N-vinylpyrrolidin-2-one as an effective 3-aminopropyl carbanion equivalent. The final preparation in Volume 75, cis-4a(S), 8a(R)-PERHYDRO-6(2H)-ISOQUINOLINONES, il lustrates the conversion of quinine via oxidative degradation to meroquinene esters that are subsequently cyclized to N-acylated cis-perhydroisoquinolones and as such represent attractive building blocks now readily available in the pool of chiral substrates. 

In fluorosulfonic acid the anodic oxidation of cyclohexane in the presence of different acids (RCO2H) leads to a single product with a rearranged carbon skeleton, a 1-acyl-2-methyl-1-cyclopentene (1) in 50 to 60% yield (Eq. 2) [7, 8]. Also other alkanes have been converted at a smooth platinum anode into the corresponding a,-unsaturated ketones in 42 to 71% yield (Table 1) [8, 9]. Product formation is proposed to occur by oxidation of the hydrocarbon to a carbocation (Eq. 1 and Scheme 1) that rearranges and gets deprotonated to an alkene, which subsequently reacts with an acylium cation from the carboxylic acid to afford the a-unsaturated ketone (1) (Eq. 2) [8-10]. In the absence of acetic acid, for example, in fluorosulfonic acid/sodium... 

Oxidation of diethyl 2-aUyl-2-hydroxypentanedioate by RnCyaq. Na(IO )/ CHjCN-EtOAc gave triethyl homocitrate and the corresponding lactone [209]. Oxidation of cyclopentene to glutaric acid by RnCyaq. Na(C10)/CCl or CH Cl showed that addition of CHjCN and also NaOH greatly improved yields [210]. Perfluoro alkenes were cleaved by Ru02/IO(OH)j, Na(ClO) or CH COOOH/water-Freon 113 to carboxylic acids CO was also formed or, in the case of perfluoropro-pene, pefluoroacetic acid and COF (Table 3.6) [211]. 

NT533 Chuman, T., and M. Noguchi. Isolation of a new terpenoid acid 2-methyl-5- isopropyl 1 -cyclopentene-1 -carboxylic acid from Turkish tobacco. Agr Biol Chem 1975 39 567-568. 

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... 

In a similar manner, l-cyclopentene-3-carboxylic acid (67a) and lV-t-Boc-(S)-3,4-didehydroproline (67b) can be transformed to methyl c/s-2-hydroxycyclopentane-l-carboxylate (70a) and methyl (3R, 2S )-7V-t-Boc-3-hydroxyprolinate (70b) in 67% and 76% overall yields (4 steps), respectively (equation 28)91. 

---