Reactions of epoxides—XXIV

Blackett, B. N.; Coxon, James M.; Hartshorn, Michael P.; Richards, K.

doi:10.1016/s0040-4020(01)83247-6

Cited by 30 publications

(7 citation statements)

References 16 publications

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“…As the conditions were those used in thc reduction of ketones 171 having a centre of asymmetry a t the a-position, and which are known t o proceed without raccmisation, we did not consider epimerisation as a possibility. This rearrangement would be analogous t o the known rearrangemcnt of fluorohydrins to the corresponding 0x0 compounds under boron trifluoride etherate [6].…”

Section: Methodsmentioning

confidence: 73%

Transformations of 9 α, 10 α‐Epoxy‐Hexahydrocannabinol Acetate

Petrzilka

Prasad

Schmid

1976

Helvetica Chimica Acta

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Summary. 9a, l0a-Epoxy-hexahydrocannabinol acetate 1 in presence of boron trifluoride etherate rearranged to a fluoro compound 6 and to a ketone 5 , and in perchloric acid to compound 11. The fluoro compound 6 had been considered erroneously in earlier literature as 4. Compounds 6 and 11 were produced by the initial opening of the epoxide followed by the acetyl transfer from the neighbouring phenolic group.Tetrahydrocannabinol acetates 2 and 3, on oxymercuration-demercuration followed by reduction gave the known 9 a-hydroxy-hexahydrocannabinol (13).In an earlier communication [l], we described the synthesis of (-)-11-hydroxyds-Ga, 10a-trans-THC (THC = tetrahydrocannabinol). In the present paper we report some transformations of epoxy acetate 1 and the results of oxymercuration-demercuration experiments on d8-and 49-6a, 10a-trans-THC acetates 2 and 3 respectively.The rearrangement of 9a, lox-epoxy-HHC acetate 1 (HHC = hexahydrocannabinol) with boron trifluoride etherate was reported earlier by Mechoulam et al. [2]. A fluorine containing compound and a ketone were isolated from this reaction and were assigned structures 4 and 5 respectively. Being interested in examining the biological activity of fluorine containing cannabinoids, we selected the above reaction with the intention of obtaining compound 7 by the deacetylation of compound 4.A reinvestigation including the NMR. data (i.e., the hydroxy proton chemical shift at 6.82 and the aromatic protons chemical shiftsl) at 6.24 and 6.30) of the fluoro compound led us to believe that the fluoro compound may have structure 6 , the formation of which involves migration of acetyl from the neighbouring phenolic group to the hydroxyl at C(10). This assumption was supported by the fact that the above fluoro compound can be recovered unchanged from i) methanolic sodium hydroxide solution at room temperature and ii) from refluxing aqueous methanol containing sodium hydrogencarbonate ; conditions that were known for the deacetylation of cannabinoid derivatives with an acetyl group on the phenolic func-The fluoro compound on acetylation with acetic anhydride and pyridine yielded an acetyl derivative 8 which showed the two aromatic protons at 6.34 and 6.54, as expected a downfield shiftl) compared to the similar proton chemical shift values in the parent compound. The acetyl derivative 8 could be selectively deacetylated to 1) A correlation of aromatic proton chemical shift values of known cannabinoid derivatives showed that the two aromatic protons appear in the range 6.00-6.30 ppm in cannabinols and at 6.34-6.56 ppm in cannabinoid acetates [l].

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Section: Methodsmentioning

confidence: 73%

Transformations of 9 α, 10 α‐Epoxy‐Hexahydrocannabinol Acetate

Petrzilka

Prasad

Schmid

1976

Helvetica Chimica Acta

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“…Previous literature data reported the partial characterization of these compounds, [7,10,11] but from these data we were unable to distinguish between the two epoxides due to incoherent NMR results. [10,11] With the techniques now available (NMR spectroscopy and X-ray crystallography) we concluded that several previous NMR assignments are not correct. The chemical shift of H-4 in 4,5β-epoxycholestane (2a) was unequivocally assigned at δ ϭ 2.89 ppm instead of δ ϭ 2.98 ppm.…”

Section: Oxidation Of 4-cholestene (2)mentioning

confidence: 70%

“…The chemical shift of H-4 in 4,5β-epoxycholestane (2a) was unequivocally assigned at δ ϭ 2.89 ppm instead of δ ϭ 2.98 ppm. [11] The assignment of the carbon resonances of 4,5α-epoxycholestane (2b) [10] was corrected for C-2 (δ ϭ 15.9 instead of 22.5 ppm), C-3 (δ ϭ 22.3 instead of 28.5 ppm) and C-19 (δ ϭ 17.4 instead of 16.0 ppm). The assignment of the carbon resonances of 4,5β-epoxycholestane (2a) [10] was corrected for C-2 (δ ϭ 15.3 instead of 17.4 ppm) and for C-10 (δ ϭ 36.2 instead of 35.2 ppm).…”

Section: Oxidation Of 4-cholestene (2)mentioning

confidence: 99%

Oxidation of Δ⁴‐ and Δ⁵‐Steroids with Hydrogen Peroxide Catalyzed by Porphyrin Complexes of Mn^III and Fe^III

et al. 2004

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“…According to the literature, 27 a solution of 1,2-dibromo-2,3,3-trimethylbutane (3.30 g, 13 mmol, 1.0 equiv) and sodium methoxide (1.51 g, 2.2 mmol, 2.2 equiv) in MeOH (25 mL) was stirred at r.t. for 24 h. The reaction mixture was purified by fractional distillation to obtain the product (1.27 g, 7.2 mmol, 55%) as a colourless oil.…”

Section: ( E )-1-bromo-233-trimethylbut-1-enementioning

confidence: 99%

The Application of 1,2-Oxazinanes as Chiral Cyclic Weinreb Amide-Type Auxiliaries Leading to a Three-Component, One-Pot Reaction

Hilt¹,

Hermann²,

Fährmann³

2021

Synthesis

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1,2-Oxazines were synthesised via a copper-catalysed aerobic acyl nitroso Diels-Alder reaction from 1,4-disubstituted 1,3-dienes and N-Boc-hydroxylamine. From this, 1,2-oxazinanes were received in a novel follow-up reaction path. The stability of several 1,2-oxazines and 1,2-oxazinanes towards organometallic compounds was tested to rate their operability as cyclic chiral Weinreb amide auxiliaries. 3,6-Di-tert-butyl-1,2-oxazinane gave the best results and was introduced as chiral Weinreb amide-type auxiliary to yield chiral α-substituted ketones in a diastereomeric ratio of up to 98:2. The removal of the auxiliary can be performed with BuLi to form unsymmetrical α-chiral ketones. Thereafter, the chiral auxiliary can be re-isolated and purified by sublimation in vacuum.

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Reactions of epoxides—XXIV

Cited by 30 publications

References 16 publications

Transformations of 9 α, 10 α‐Epoxy‐Hexahydrocannabinol Acetate

Transformations of 9 α, 10 α‐Epoxy‐Hexahydrocannabinol Acetate

Oxidation of Δ⁴‐ and Δ⁵‐Steroids with Hydrogen Peroxide Catalyzed by Porphyrin Complexes of Mn^III and Fe^III

The Application of 1,2-Oxazinanes as Chiral Cyclic Weinreb Amide-Type Auxiliaries Leading to a Three-Component, One-Pot Reaction

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Reactions of epoxides—XXIV

Cited by 30 publications

References 16 publications

Transformations of 9 α, 10 α‐Epoxy‐Hexahydrocannabinol Acetate

Transformations of 9 α, 10 α‐Epoxy‐Hexahydrocannabinol Acetate

Oxidation of Δ4‐ and Δ5‐Steroids with Hydrogen Peroxide Catalyzed by Porphyrin Complexes of MnIII and FeIII

The Application of 1,2-Oxazinanes as Chiral Cyclic Weinreb Amide-Type Auxiliaries Leading to a Three-Component, One-Pot Reaction

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Oxidation of Δ⁴‐ and Δ⁵‐Steroids with Hydrogen Peroxide Catalyzed by Porphyrin Complexes of Mn^III and Fe^III