CCLXI.—Resolution of trans-cyclobutane - 1 : 2 - di-carboxylic acid

Goldsworthy, L. J.

doi:10.1039/ct9242502012

Cited by 6 publications

(9 citation statements)

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“…CCl 3 UV irradiation of racemic 11 produced an anomeric mixture of 15 in 45% yield (Scheme 3) and some cycloelimination product. The mixture consisted of about equal amounts of the two inseparable anomers as evident from the doubling of the signals in the acetal proton region d 4.8-5.2 ppm.…”

Section: Resultsmentioning

confidence: 99%

“…Cyclobutanones and cyclobutenones are the most readily available derivatives of cyclobutanes. 2 It is, therefore, rather surprising that whereas chiral cyclobutanes have been reported in the early 1900s, 3 the first optically active cyclobutanone was only reported in 1960, 4 even though cyclobutanones in their racemic forms were available much earlier. 5 Although a number of approaches to chiral cyclobutane derivatives have been developed, 6 the selective enzymecatalyzed reactions of cyclobutanes have received scant attention.…”

Section: Introductionmentioning

confidence: 97%

“…The reaction mixture was then diluted with 100 mL ether and the zinc powder filtered off. The filtrate was then washed with 5 · 100 mL satd NaHCO3 , 100 mL H 2 O, and 100 mL of brine solution. After drying over MgSO 4 , the solution was concentrated and applied on a silica dd, 1H, J = 2.0, 2.4 Hz), 2.68-2.64 (dd, 1H, J = 16.8, 0.8 Hz), 2.07 (s, 3H), 1.46 (s, 3H), 1.24 (s, 3H); 13 C NMR: d 205.7, 170.6, 65.9, 59.2, 58.4, 29.8, 29.4, 22.6, 20.7; FTIR (neat): 1781, 1741 cm À1 ; MS m/z 170 (M + ); Anal.…”

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confidence: 99%

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Enantiomeric resolution of cyclobutanones and related derivatives by enzyme-catalyzed acylation and hydrolysis

Salezadeh-Asl

Lee‐Ruff

2005

Tetrahedron: Asymmetry

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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confidence: 99%

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Enantiomeric resolution of cyclobutanones and related derivatives by enzyme-catalyzed acylation and hydrolysis

Salezadeh-Asl

Lee‐Ruff

2005

Tetrahedron: Asymmetry

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“…Correlation of (3R,4S)-(-)-Methyl 3-c/s-Methylcyclohexene-4carboxylate ( 43) and (3/?,4R)-(-)-Methyl 3-frans-Methylcyclohexene-4-carboxylate (44). The quinine salt77 of m-3-methylcyclohexene-4-carboxylic acid (41) was taken up in 300 ml of 3 N HC1 and extracted three times with 100 ml of chloroform.…”

Section: Methodsmentioning

confidence: 99%

“…The major and first eluted isomer was (3R,4R)-(-)-methyl trans- (44): [ a I 2 l~ -37.3" (e 16.6, CC&), 46.4% optically pure. VPC analysis (Carbowax 20M, 180 "C) of the epimerized ester, 0.8 g (73%), indicated the trans-44/cis-43 ratio was 3:l. The isomers were separated and isolated by preparative VPC (Carbowax 20M, 190 "C).…”

Section: (Lr2r)-(+)-trans-12-transtransand (Lrzr)-(-)-trans-l2-mentioning

confidence: 99%

Formation and thermal rearrangements of some dimers of butadiene and piperylene. Tests of the validity of thermochemical-kinetic arguments for identification of common biradical intermediates

Berson¹,

Dervan²,

Malherbe³

et al. 1976

J. Am. Chem. Soc.

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The mechanisms of the dimerization of butadiene and piperylene and the thermal rearrangements of the corresponding dimers are investigated by kinetic and stereochemical techniques. Particular attention is given to the question whether, in the Diels-Alder dimerization of the dienes la or Ib, intermediates are involved that are common to the 1,3-sigmatropic rearrangements of the corresponding [2 + 21 dimers 3a and 3b. Substituents on the terminal vinyl position of cis-1,2-divinylcyclobutane (Sa) retard the normal stereospecific boat-like Cope rearrangement to 3,4-dimethyl-cis,cis-cycloocta-1,5-diene and permit the detection of a new "nonboat" process, whicjl leads to a stereoisomeric prbduct. The boat-like rate constant declines with increasing terminal cis-methyl sustitution in the series Sa > cTT-8 > cCT-8 > cCC-8. The total range of the effect amounts to a factor of 1.81 X lo5. The trans-1,2-dipropenylcyclobutanes also give Cope rearrangement products, but this reaction occurs exclusively by an indirect mechanism: prior epimerization to the cis isomer followed by Cope rearrangement of the latter. The rearrangement of trans-3,4-dimethyl-cis,trans-cycloocta-1,5-diene (16) to cis-3,4-dimethyl cis,cis-cycloocta-1,5-diene (lo), involving overall epimerization at one asymmetric center and geometric isomerization at one olefinic site, proceeds by a two-step mechanism in which cis.-1,2-trans,trans-dipropenylcyclobutane (cTT-8) is an intermediate. The 1,3-sigmatropic rearrangement of (lR,2R)-(+)-trans-1,2-divinylcyclobutane (3a) gives (R)-(+)-4-vinylcyclohexene (2a) with 7.7% preservation of enantiomeric purity (corrected for competing racemization of 3a). This corresponds to 54% inversion and 46% retention of configuration of the migrant carbon. By attaching stereochemical labels to the terminal vinyl positions as in optically active tTT-9 and tCT-9, the stereochemistry of the 1,3-sigmatropic rearrangement can be subdivided into the four possible pathways (Schemes IX and X), suprafacial inversion, antarafacial retention, suprafacial retention, and antarafacial inversion. In this way, it can be shown that relative rates through these four pathways are, respectively, 50.2,6.0,41.1, and 2.7 from tTT-9, and 49.5, 2.8.46.8, and 0.9 from tCT-9. These results can be fitted by a biradical mechanism, but are more fruitfully interpreted as mainly the outcome of two competing concerted reactions, one allowed (supra facial inversion) and one forbidden (suprafacial retention). The absence of any substantial antara contribution in the dipropenyl systems rules out a stereorandom biradical intermediate in the tTT-9 and tCT-9 rearrangements and makes it unlikely in the divinyl system 3a. The Diels-Alder dimerization of trans-penta-1,3-diene-t~a~s-l -d (45, Scheme XIV) in both the exo and endo orientations gives exclusively the product of reaction cis-on-the-diene,&-on-the-dienophile. This is consistent with a concerted [4s + 2s]cycloaddition and rules out common intermediates in the formation of product tT-13 and cT-12 from the two alte...

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