Methyl 3-cyclopentene-1-carboxylate

Methyl tert-butyl ether Propane, 2-methoxy-2-methyl- (9) (1634-04-4), 75, 31 Methyl 3-cyclopentene-1 -carboxylate, 75, 197... 

Interestingly, the carbonylation of 4-en-2-ynyl methyl carbonates provides cross-conjugated 4-oxo-5-aIkyUdene-2-cyclopentene-carboxylates in cases where no relevant... 

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... 

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. 

This collection begins with a series of three procedures illustrating important new methods for preparation of enantiomerically pure substances via asymmetric catalysis. The preparation of 3-[(1S)-1,2-DIHYDROXYETHYL]-1,5-DIHYDRO-3H-2.4-BENZODIOXEPINE describes, in detail, the use of dihydroquinidine 9-0-(9 -phenanthryl) ether as a chiral ligand in the asymmetric dihydroxylation reaction which is broadly applicable for the preparation of chiral dlols from monosubstituted olefins. The product, an acetal of (S)-glyceralcfehyde, is itself a potentially valuable synthetic intermediate. The assembly of a chiral rhodium catalyst from methyl 2-pyrrolidone 5(R)-carboxylate and its use in the intramolecular asymmetric cyclopropanation of an allyl diazoacetate is illustrated in the preparation of (1R.5S)-()-6,6-DIMETHYL-3-OXABICYCLO[3.1. OJHEXAN-2-ONE. Another important general method for asymmetric synthesis involves the desymmetrization of bifunctional meso compounds as is described for the enantioselective enzymatic hydrolysis of cis-3,5-diacetoxycyclopentene to (1R,4S)-(+)-4-HYDROXY-2-CYCLOPENTENYL ACETATE. This intermediate is especially valuable as a precursor of both antipodes (4R) (+)- and (4S)-(-)-tert-BUTYLDIMETHYLSILOXY-2-CYCLOPENTEN-1-ONE, important intermediates in the synthesis of enantiomerically pure prostanoid derivatives and other classes of natural substances, whose preparation is detailed in accompanying procedures. 

SYNS 2-CYCLOPENTENYL-4-HYDROXY-3-METHYD 2-CYCLOPENTEN-l-ONE CHRYSANTHEMATE 3-(2-CYCLOPENTEN-l-YL)-2-METHYL-4-OXO-2-CYCLOPENTEN-l-YL CHRYSANTHEMUMATE 3-(2-CYCLOPENTENYL)-2-METHYL-4-OXO-2-CYCLOPENTENYL CHRYSANTHEMUMMONO-CARBOXYLATE CYCLOPENTENYLRETHONYL CHRYSANTHEMATE ENT 22,952... 

C6H802 1 cyclopentene-1-carboxylic acid 1560-11-8 28.61 1.0403 2 7712 C6H10N2 1-ethyl-3-methyl-1 H-pyrazole 30433-57-9 20.00 0.9360 1... 

C8H13N02 ethyl 2-amino-1 -cyclopentene-1 -carboxylate 7149-18-0 491.48 43.066 2 14570 C8H140 6-methyl-2-hepten-4-one 49852-35-9 443.15 38.450 1,2... 

Cyclopropene esters give aminobicyclo[2.1.0]pentane derivatives, which can undergo ring-opening reactions to cyclopentenes For example, methyl 3,3-dimethylcyclo-propene-l-carboxylate (37), obtained by photolysis of the corresponding pyrazolinic derivative, reacted with the diquinanic enamine 36 to give a mixture of the alkylation product 38 and the [2 + 2] cycloadduct 39 which, on acid treatment, was transformed into the triquinanic cyclopentene alcohol 40 (equation 6). 

Cyclopentene-1-carboxylic acid, 2-methyl-5-(1-methylethyl)- COOH IV.A-3... 

Cyclopropaneacrylic acid, 3-carboxy-a,2,2-trimethyl-, 1-methyl ester, ester with 4-hydroxy-3-methyl-2-(2,4-pentadienyl)-2-cyclopenten-1-one. See Pyrethrin II Cyclopropane carboxylic acid, 3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl-, (2-methyl (1,r-biphenyl)-3-yl) methyl ester, (z)-. See Bifenthrin... 

Treatment of cyclopentene-2-carboxylic acid with performic acid produced approximately equal amounts of the corresponding cis-2,trans-3- and trans-2,cis-3-dihydroxycyclopentane-r-1-carboxylic acids which can be separated chromato-graphically via their methyl esters. The rrans-2,cis-3-compound was cyclized by tosyl chloride to the y-lactone whereas the cis-2jtrans-3-diol gave a trans-3-tosyloxy-P-lactone in an unprecedent reaction for a P-hydroxy-acid. The assignments of configuration and structure are supported by substantial chemical and spectoscopic evidence. 

In addition to a,y -unsaturated ketones, a,yff-unsaturated esters also undergo cyclization, albeit at much slower rates than the corresponding a -unsaturated ketones. Treatment of methyl acrylate (49) with silylallene 34 at 25 °C (rather than the standard -78 °C) in the presence of TiCU furnished the expected cyclopentene 50 in 49% yield. To access carboxylate derivatives, Danheiser has reported the use of a, -unsaturated acylsilanes as the electrophilic component in the annulation process producing the corresponding acylsilane substituted cyclopentenes. " The acylsilane can then... 

Cyclopentene reacts exclusively to give cyclopentane carboxylic acid. Formation of methyl-substituted four-membered rings has not been observed. Also cyclohexene reacts to give nearly 90 % of cyclohexane carboxylic acid, whereas cycloolefins containing 8, 9 and 10 C-atoms in the ring generally do not form secondary acids. The performance of the methyl-substituted cycloalkenes can be seen from fig. 18. 

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