The reaction of epoxides with carboxylic acids

Hickinbottom, W. J.; Hogg, D. R.

doi:10.1039/jr9540004200

Cited by 14 publications

(8 citation statements)

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“…Reacting styrene oxide with acetic acid a t room temperature gave mixtures of the two monoacetates 3a and 4a (Table I), in accordance with that found earlier by Berti et al (1) and Cohen et al (6), and not 2-acetoxy-1-phenylethanol (10). At about +3' only 2-acetoxy-2-phenylethanol l a was obtained, the first time this has been demonstrated and vindicating suggestions by others (1,6).…”

Section: Resultssupporting

confidence: 79%

“…And styrene oxide is no different from other epoxides in the appearance of conflicting reports on its behavior during ring-opening reactions. With acetic acid, for instance, Hickinbottom and Hogg (10) claim that attack is predominantly a t the primary carbon to give 2-acetoxy-1-phenylethanol 40, whereas others (1, 6) claim that the secondary carbon is preferentially attacked giving largely 2-acetoxy-2-phenylethanol3a. The present study finds support for the latter claim and provides a method which may prove helpful in other systems.…”

Section: Resultsmentioning

confidence: 99%

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Isomeric Mixture Analysis of Some Ring-opening Reactions of Styrene Oxide

Hocking¹

1974

Can. J. Chem.

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Mixtures of ring-opened and other products of reactions of acetic or benzoic acids, or ethanol, or phenol with styrene oxide under various conditions can be qualitatively and quantitatively analyzed without isolation of the components by the use of n.m.r. This method, in the case of the ester products, avoids confusing the initial ring-opening result with the results observed after subsequent acyl migrations which readily occur in this type of system.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Isomeric Mixture Analysis of Some Ring-opening Reactions of Styrene Oxide

Hocking¹

1974

Can. J. Chem.

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“…The distillate contained one product besides the unchanged olefin. The product was collected by preparative GLC (5 ft, CW at 120°) and was identified as rerr-butyloxirane (15) by comparison with an authentic sample prepared from 14 with mchloroperbenzoic acid, bp [35][36] °C (40 mm) (lit.33 89-90.5 °C): NMR (CC14), 0.90 (s, 9 H), 2.44-2.66 (m, 3 H). The yield of the epoxide was 69%, along with 22% of the unchanged olefin.…”

Section: H)mentioning

confidence: 99%

Photooxidation of olefins sensitized by .alpha.-diketones and by benzophenone. A practical epoxidation method with biacetyl

Shimizu¹,

Bartlett²

1976

J. Am. Chem. Soc.

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Photooxidation of nine olefins in benzene solution with oxygen and benzil leads to epoxides as the main product in yields ranging from 5% in 60 min for trans-stilbene to 98% in 15 min for norbornene. From cis or trans acyclic olefins the epoxide is always trans. Competing processes include formation of allylic hydroperoxides from olefins (2.3-dimethyl-2-butene and 1,2-dimethylcyclohexene) that are quite reactive toward singlet oxygen, and energy transfer with cis,trans isomerization of olefins with lower lying triplet states (stilbene). Recovery of b e n d is high, showing that it is neither consumed stoichiometrically in the process nor oxidized directly in effective competition with the photoepoxidation. The action of biacetyl as a photosensitizer is similar to that of benzil but is attended by much more destruction of the diketone and yields epoxide with a wider range of olefins. Seven of the 18 olefins in Table I11 are converted to epoxides in yields of 90% or more, making this a useful preparative method. Benzil and biacetyl are compared with the T,T* photosensitizer fluorenone, which can produce singlet oxygen but gives no epoxidation, and with the n-r* sensitizer benzophenone, in which cycloaddition to an olefin to give oxetane is an important competing process and becomes the major course of the reaction with norbornene. The nature of the mechanism is discussed.Dye-sensitized photooxidation reactions have been extensively investigated and the results are consistent with the singlet oxygen mechanism. Photooxidation with n-x* triplet sensitizers, however, presents a less simple picture. A free-radical mechanism is indicated in benzophenone-sensitized oxidation of 2-pr0panol.~ Gollnick and co-workers have pointed out that n-A* triplet sensitizers can also generate singlet ~x y g e n .~ We report here the results of photooxidation of various olefins with benzil and biacetyl as sensitizers and show that the present photooxidation is quite different from the singlet oxygen oxidation and also from radical-chain autoxidations.Photooxidation with Benzil. The irradiation4 of a benzene solution of 1,2-dimethylcyclohexene (1,0.5 M) and benzil (0.1 M) with a Hanovia 450-W medium-pressure mercury lamp a t 0" for 15 min, oxygen being bubbled through during the irradiation, gave allylic hydroperoxide (2a) and epoxide (3) in 58 and 12% yield, respectively, together with 30% of recovered olefin. Benzil was recovered almost quantitatively. Table I shows the contrast between these results and either the dye-sensitized oxidation5-' or the autoxidation Important differences between dye and benzil sensitizations appear also in the oxidation of aromatic olefins. Benzil-sensitized oxidation of five aromatic olefins gave epoxides as shown in Table 11, whereas it is known that these aromatic olefins are converted very slowly to ketones by long exposure to singlet PhRC=O + R'R"C=O "very slow" ~x y g e n .~ A characteristic feature is the stereochemistry of epoxide formation: only trans-epoxide was obtained independently of the geome...

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“…With strong acids the first step is protonation and SnI ring opening, followed by reaction with the carboxylate ion. 32 With formic acid this is true and carbonium ion 25 leads to the formation of by-products. With the less acidic higher molecular weight acids, ring opening may be less SnI in character so that little free carbonium ion is formed.…”

Section: E Reaction With Epoxidesmentioning

confidence: 99%