Methoxyl group migration to carbenoid centers

Gassman, Paul G.; Creary, Xavier

doi:10.1016/s0040-4039(01)94327-8

Cited by 6 publications

(5 citation statements)

References 5 publications

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“…A possible explanation is proposed in Figure for the anomalous behavior that has been observed for the enol carbonates. By analogy with other oxygen-substituted alkenes, initial formation of a σ-complex 19 , followed by primary ozonide 20 formation, would have been expected . This pathway is viable where an explanation of enhanced reactivity is required.…”

Section: Discussionmentioning

confidence: 98%

“…By analogy with other oxygen-substituted alkenes, initial formation of a σ-complex 19, followed by primary ozonide 20 formation, would have been expected. 5 This pathway is viable where an explanation of enhanced reactivity is required. In contrast, reaction with the electrophilic reagent occurring first at the molecule's center of highest electron density, the carbonyl, could reversibly produce either an unusual σ-complex 17 or a [3 + 2] addition product 18.…”

Section: Discussionmentioning

confidence: 99%

“…As demonstrated at low temperatures, many simple alkenes form an ozone-olefin charge-transfer complex, 4 prior to ozone's electrophilic or dipolar addition. In the case of electronrich, oxygen-substituted double bonds, the formation of a σ complex 5 from electrophilic attachment of ozone at the center of highest electron density appears to then proceed directly to primary ozonide formation.…”

Section: Introductionmentioning

confidence: 99%

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Reactivity of Enol Carbonates with Ozone

et al. 1999

J. Org. Chem.

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Several dienes of varying steric bulk containing an enol carbonate have been synthesized and reacted selectively with ozone at the isolated double bonds. Rate measurements have been made for ozonolysis in a series of substituted cyclohexenes to demonstrate the unusually slow reactivity of the enol carbonate. Proton and carbon NMR chemical shifts have been presented to show that the enol carbonate is not particularly electron deficient in its double bond. Calculation of partial charges from the Mulliken population analysis shows good correlation with the NMR data. The results suggest a carbonate association with ozone that slows the rate of carbon-carbon bond cleavage.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reactivity of Enol Carbonates with Ozone

et al. 1999

J. Org. Chem.

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“…A precise mathematical relationship between rates and amount of rearrangement for 1 could not be deduced,20 but in the same solvent and under the same conditions a larger amount of rearranged product possibly reflects a larger acceleration. 14 In other words, if two phenomena (rate enhancement and rearrangement) are produced by the same cause (bridging) they are necessarily related. As this point was also recognized by the previous workers,21 it needs no further elaboration.…”

Section: Methodsmentioning

confidence: 99%

Steric and conformational effects in the solvolysis of ring-fused tertiary cyclopropyl derivatives

Creary¹,

Keller²,

Dinnocenzo³

1978

J. Org. Chem.

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“…Recently, direct evidence of dioxetane formation in an acenaphthylene derivative oxygenated at the 1 and 2 positions has been obtained (25). Ozonolysis of the dimethoxynorbornene derivative 27 forms -50% of 28 (26), a product analogous to 7.…”

Section: Electron Transfer In Other Ozonolysesmentioning

confidence: 99%

Ozonolysis of tetramethoxyethene

Kopecky¹,

Molina²,

Rico³

1988

Can. J. Chem.

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. Can. J. Chem. 66, 2234Chem. 66, (1988. Ozonolysis of tetramethoxyethene 1 produces 20-40% of dimethyl carbonate 3, 35-60% of methyl trimethoxyacetate 7, and 20-35% of the dioxetane 8 of 1. Yields vary with initial concentration of 1, temperature, and solvent. Singlet oxygen is produced, which reacts with 1 to form 8 and can be trapped with 2,5-dimethylfuran. No evidence for the formation of the molozonide of 1 was obtained. Up to 2.5 moles of 1 are consumed per mole of ozone. Ozonolysis of a mixture of 1 and 2,3-dimethyl-2-butene 12 gave the epoxide of 12 and three times the expected amount of the allylic hydroperoxide of 12. A competing radical chain oxidation reaction is proposed to account for these products and the stoichiometry of the ozonolysis. The initial reaction in the ozonolysis of 1 is proposed to be an electron transfer reaction that is calculated to be exothermic by >35 kcal/mol. The resulting radical ions initiate the radical chain oxidation and combine to form the oxygenated epoxide 9 of 1. Loss of singlet oxygen from 9 forms the epoxide 10, which rearranges to 7. At -95'C the zwitterion from 10 is trapped by CD30D to produce a mixture of 7 with one a 0CD3 group and pentamethoxyethanol with one P 0CD3 group from which a CH30D group is lost at --10°C to form more deuterated ester. L'ozonolyse du tCtramCthoxyCthkne (1) foumit de 20 40% de carbonate de dimdthyle (3), de 35 a 60% de trimCthoxyacCtate de mtthyle (7) et de 20 a 35% du dioxCtane 8 du compost5 1. Les rendements varient avec la concentration initiale du composC 1, avec la temperature et avec le solvant. I1 se produit de I'oxygkne singulet qui rCagit avec le compost 1 pour donner du produit 8; on peut le pitger avec du dimithyl-2,5 furanne. On n'a pas obtenu de rCsultats suggCrant qu'il se forme du molozonide du composC 1. Pour chaque molCcule d'ozone, il y a 2,5 moles du composC 1 qui sont consommCes. L'ozonolyse d'un mClange du composC 1 et du dimethyl-2,3 butkne-2 (12) fournit 1'Cpoxyde 12 ainsi que de I'hydroperoxyde allylique de 12 qui se forme en quantitts trois fois plus grandes que ce qu'on avait prCvu. On suggkre I'existence d'une reaction competitive d'oxydation radicalaire en chaine pour expliquer la formation de ces produits ainsi que la stoechiomttrie de l'ozonolyse. On suggkre que la rtaction initiale, lors de l'ozonolyse du composC 1, est une rCaction de transfert Clectronique qui, d'aprks nos calculs, serait exothermique par >35 kcal/mol. Les ions radicaux qui en rCsultent initient la reaction d70xydation radicalaire en chaine et se combinent pour former l'tpoxyde oxygCne 9 du composC 1. Par perte d'oxygkne singulet, le composC 9 foumit 1'Cpoxyde 10 qui se transpose en composC 7. A -95"C, le zwitterion provenant du compost 10 est piCgC par le CD30D pour conduire a un mClange du composC 7 portant un groupement 0CD3 en a et de pentamCthoxyCthano1 portant un groupement 0CD3 en P qui, par perte de CH30D a --1O0C, forme d'autre ester deutCrC.[Traduit par la revue] IntroductionA general synthesis of tetraalkoxy-1,2,4,5-tetrox...

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Methoxyl group migration to carbenoid centers

Cited by 6 publications

References 5 publications

Reactivity of Enol Carbonates with Ozone

Reactivity of Enol Carbonates with Ozone

Steric and conformational effects in the solvolysis of ring-fused tertiary cyclopropyl derivatives

Ozonolysis of tetramethoxyethene

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