Cyclopentane-l-carboxylate

An aq. soln. of K-iododichloride prepared from iodine chloride and KGl according to A. A. Larsen et al., Am. Soc. 78, 3210 (1956) added all at once with vigorous stirring to a soln. of l-(4-aminophenyl)cyclopentane-l-carboxylic acid in 0.1 iV HGl, stirring continued for 2 hrs., then satd. NaHSOg-soln. added to remove excess iodine l-(4-amino-3,5-diiodophenyl)cyclopentane-l-carboxylic... 

The readily available methyl 3,3-dimethylcyclopropene-l-carboxylate (III/54) undergoes [2+2] cycloaddition with enamines e.g. the morpholine derivative III/55 to give 2-aminobicyclo[2.1.0]pentane derivatives, e.g. III/56. These compounds are transformed into cyclopentane derivatives, e.g. methyl 4-hydroxy-2,5,5-trimethyl-1-cyclopentenecarboxylate (III/57) by treatment with dilute mineral acids. 

The selectivity for the alkene-substituted cycloadduct is also almost complete in the case of the reaction of l-methylene-2-(trimethylsilyl)cyclopropane (5) with dimethyl fumarate, which results in a 78% yield of dimethyl /ra x-4-(trimethylsilylmethylene)cyclopentane-l,2-di-carboxylate (7). Interestingly, only one of the stereoisomeric dimethyl 4-methylene-3-(trimethyl-silyl)cyclopentane-l,2-dicarboxylates [the (/ , / , / )-isomer 8] is formed selectively. ... 

Mean while, to a mixture of 190.0 g 2-bromo-4-fluoro-aniline (1 mol) and 0.6 L water at room temperature was added 3 mol concentrated HCI the resulting thick white slurry was cooled to 0°C. A solution of 1 mol NaN02 in 0.7 L water was added slowly over 25 min, at such a rate as not to exceed an internal temperature of 10°C, and the reaction was aged for 30 min before filtration to remove any insoluble precipitate. This filtered diazonium solution was added to the prepared sodium carboxylate solution at 0°C dropwise over a period of 40 min (Note If added to the solution of sodium carboxylate, then it was not necessary to acidify the sodium carboxylate with concentrated HCI.) The resulting thick yellow slurry was stirred to room temperature, filtered, and dried under a stream of nitrogen to give 270.9 g (4 1 ratio) l-( /Z)-cyclopentane-l,2-dione (2-bromo-4-fluorophenyl)hydrazone as a yellow solid, in a yield of 95%, m.p. 182-187°C. 

To the prepared sodium carboxylate solution at 0°C was added the filtered diazonium solution dropwise over 40 min at a temperature range of 0-4°C. The resulting thick yellow slurry was stirred to room temperature, filtered, and dried under a stream of nitrogen to give 95% (l /Z)-cyclopentane-l,2-dione (2-bromo-4-fluorophenyl) hydrazone, as a yellow solid of steric mixture in 4 1 ratio, m.p. 182-187°C. 

Oxidative rearrangements, via oxythallation, have been improved in yield and selectivity by the use of thallium(iii) nitrate supported on clay rather than in methanolic solution. Thus, cyclohexene gave an 85% yield of dimethoxymethyl-cyclopentane while 1-tetralone, which normally gives a complex mixture of products, gave a 1 1 mixture of methyl indane-l-carboxylate and 2-methoxytetralone. An efficient, large-scale procedure for the direct cis-dihydroxylation of olefins has been reported. The oxidant is t-butyl hydroperoxide and the catalyst osmium tetroxide, with the reaction conducted under alkaline conditions (E%N OH ), so facilitating a rapid turnover of catalyst via enhanced hydrolysis of the osmate esters. The method appears to be more advantageous for the more substituted olefins than the Hofmann and Miles procedure. 

N 22 2,5-Norbomadiene-2-carboxylic acid, ethyl ester N 14 Norbomene. See Cyclopentane, l,3-/mwj-vinylene polymer (alt) N 24 Nylon. See under name of acid source material. 

Amines react with ]8-dicarbonyl compounds such as acetylacetone, benzoylacetone or cyclopentan-2-one-l-carboxylic add ethyl ester to form enamines. These enamines (54) like the o-hydroxybenzylidene derivatives are stabilized by hydrogen bonding. The protecting group is removed by treating the corresponding derivative with dilute add . 

I With ethyl (2-phenacyl)cyclopentan-l-one-2-carboxylate (X), the following reactions are carried out ... 

Addition of the chelated enolate of the S-oxo ester moiety of a 2,8-dioxo-6-alkenoate 1 under thermodynamic control at 25 °C using stoichiometric or catalytic amounts of sodium hydride in benzene results in the formation of tram-2-oxo-5-(2-oxoalkyl)-l-cyclopentane-carboxylate 2 exclusively. 

C—H bond 174-280,28i por comparison, only trace amounts of cyclopentane resulted from the CuS04-catalyzed decomposition of 1 -diazo-2-octanone or l-diazo-4,4-dimethyl-2-pentanone 277). It is obvious that the use of Rh2(OAc)4 considerably extends the scope of transition-metal catalyzed intramolecular C/H insertion, as it allows for the first time, efficient cyelization of ketocarbenoids derived from freely rotating, acyclic diazoketones. This cyelization reaction can also be highly diastereo-selective, as the exclusive formation of a m is-2,3-disubstituted cyclopentane carboxylate from 307 shows281 a). The stereoselection has been rationalized by... 

Intramolecular carbene C-H insertion frequently leads to the formation of five-membered rings [967,990,1021,1113-1128], In particular l-diazo-2-alkanones tend to yield cyclopentanones exclusively when treated with rhodium(ll) carboxylates. The use of enantiomerically pure catalysts for diazodecomposition enables the preparation of non-racemic cyclopentane derivatives [1005,1052,1074,1092,1129]. Intramolecular 1,5-C-H insertion can efficiently compete with 1,2-C-H insertion... 

Threonine 5.85 1-Amino-l-cyclopentane carboxylic acid 14.78 l-Amino-l-(4-piperidinyl)-carboxylic acid 19.22... 

Phenyl-l-cyclopentane carboxylic acid was produced in the result of reaction of 1-phenylcyclopentane carbonitrile with sulfuric acid. 

Phenyl-l-cyclopentanecarbonyl chloride was obtained by treatment of 1-phenyl-l-cyclopentane carboxylic acid with thionyl chloride. 

Xenon difluoride reacted with various carboxylic acids, and the type of transformation depends on the structure of the organic molecules35-39. The reaction with primary carboxylic acids involves free-radical intermediates. 6-Hexenoic acid was used as a free-radical clock device in which a A abs of 1.1 x 106 M-1s-1 at 25 °C was determined, while the alkyl radical was also spin-trapped to give an ESR signal37. The primary free radical was trapped by internal cyclization, and (fluoromethyl) cyclopentane in 25% yield was formed, while 6-fluoro-l-hexene could be formed from a radical or ionic intermediate, but 1-fluo-rocycloclohexane was not observed as a product (Scheme 42). 

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