2-Cyclopentanone carboxylic acid esters

Limited progress has been achieved in the enantioselective hydrogenation of a,/ -unsaturated carboxylic acid esters, amides, lactones, and ketones (Scheme 26.10). The Ru-BINAP system is efficient for the hydrogenation of 2-methy-lene-y-butyrolactone, and 2-methylene-cyclopentanone [98]. With a dicationic (S)-di-t-Bu-MeOBIPHEP-Ru complex under a high hydrogen pressure, 3-ethoxy pyr-rolidinone could be hydrogenated in isopropanol to give (R)-4-ethoxy-y-lactam in 98% ee [39]. 

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... 

Oxobutyl)cyclopentanone-2-carboxylic Acid Ethyl Ester. 

A different approach was adopted in the synthesis by Justoni and Pessina (111). The Japp-Klingemann reaction of p-benzyloxyphenyl-hydrazine with cyclopentanone carboxylic ester gave the p-benzyloxy-phenylhydrazone of a-ketoadipic acid (XIV) Fischer cyclization of the corresponding dimethyl ester then yielded 5-benzyloxyindole-2-car-boxylic-3-jS-propionic acid (XV). Decarboxylation of XV followed by Curtius degradation and debenzylation eventually afforded 5-hydroxy-tryptamine. 

Pyrethrum (Chrysanthemum) dnerarifolium (Asteraceae) namely cinerin I (CMC cineralone ester), cinerin II (CDC monomethyl ester cinerolone ester), pyrethrin I (CMC pyrethrolone ester) and pyrethrin II (CDC monomethyl ester pyrethrolone ester). The chrysanthemum carboxylic acids are cyclopropane-based monoterpenes and cineralone and pyrethrolone are cyclopentanone monoterpene alcohols. The pyrethrins (and their insecticidal synthetic derivatives) are toxic to insects through keeping cell membrane voltage-gated Na+ channels open and thus impairing neurotransmission. 

OXOBUTYL)CYCLOPENTANONE-2-CARBOXYLIC ACID ETHYL ESTER. 

Oxobutyl)cyclopentanone-2-carboxylic acid ethyl ester Cyclopentanecarboxylic acid, 2-oxo-1-(3-oxobutyl)-, ethyl ester (10) (61771-81-1)... 

Cyclopentanone-2-carboxylic acid ethyl ester Aldrich Ethyl... 

Treatment of dehydrooxoheteratisine (CD) with potassium tert-butoxide in feri-butanol leads to the y-lactone carboxylic acid, characterized as its methyl ester (CDXIV) [1787 cm i, (y-lactone), 1748 cm (cyclopentanone), 1728 cm i (C02Me, 1648 cm i (S-lactam)]. Its formation by cleavage of the initial retroaldol product (CDXII) to a S-lactone carboxylic acid (CDXIII) and subsequent isomerization to the y-lactone provides decisive proof for location of the tertiary hydroxyl at a position j8 to both the cyclopentanone and S-lactone carbonyls and four carbons removed from the S-lactone ether oxygen. 

OXOBUTYL)CYCLOPENTANONE-2-CARBOXYLIC acid ethyl ester. 

The 11-deoxyprostaglandins, a group not found in nature, have been synthesised by workers at the Ayerst Laboratories [115, 148-151]. 11-Deoxy-PGFy (LXXI) has been prepared starting from the enone (LXXII), obtained by the action of sulphuric acid on the monobromo derivative of the condensation product of ethyl 2-cyclopentanone carboxylate and (o-bromoethylheptanoate [115, 148, 149]. Reaction of (LXXII) with acetone cyanohydrin, hydrolysis of the ester-nitrile to the dicarboxylic acid and reaction with methanol and />-toluenesulphonic acid gave the mono ester (LXXIII) of which the acid chloride was converted with heptyne and aluminium chloride into the chlorovinylketone (LXXIV). The sequence was then completed by replacement of chloro with methoxyl, ester hydrolysis and borohydride reduction to the unsaturated ketone (LXXV) followed by borohydride reduction of the side chain carbonyl group. 

Phosphine-AgOTf complexes are known to promote Michael addition reactions. Kobayashi and Shirakawa have achieved asymmetric Michael addition of P-ketoester to nitroalkenes catalyzed by (R)-Tol-BINAP-AgOTf in water [68]. When cyclopentanone-2-carboxylic acid tert-butyl ester (50) and trans- -nitrostyrene (51) were used as substrates, the Michael adduct (52) was obtained in 71% yield with 77 23 diastereomeric ratio. The major diastereomer showed 78% ee (Scheme 18.19). 

Benzyl alcohol at 155.4°C Tetrahydrofuran, acetone-carbon disulfide mixtures, methyl ethyl ketone Toluene, xylene, methylene chloride, ethylene chloride, perchloroethylene-acetone mixtures, 1,2-dichlorobenzene, tetrahydrofurfuryl alcohol, dioxane, acetone-oarbon disulfide mixtures, cyclopentanone, diisopropyl ketone, mesityl oxide, isophorone, dimethyl-formamide, nitrobenzene, hexamethyl-phosphoramide, tricresyl phosphate Aliphatic and aromatic hydrocarbons, vinyl chloride monomer, alcohols, glycols, aniline, acetone, carboxylic acids, acetic anhydride, esters, nitroparaffins, carbon disulfide, nonoxidizing mineral acids, concentrated alkalies... 

Conjugation has a great influence on the structure of aliphatic and alicyclic compounds. Thus, the existence of an amino form has been established (in addition to the extreme case of aromatic amines17) for all compounds where the double bond is conjugated with a carbonyl group (or its equivalent),12 with esters12,18 and nitriles of a,/8-un-saturated /8-amino acids,519,20 and with /8-amino-ketones. The /3-keto-esters ethyl 2-cyclopentanone- 1-carboxylate and ethyl 2-cyclo-hexanone-l-carboxylate exist as mixtures containing 95% of the keto... 

---