Steroids and sex hormons. Part 264. Lewis acid catalyzed reversible [1,5]‐hydride shift in 3,19‐epoxy‐steroids

Acklin, Georg; Graf, Walter

doi:10.1002/hlca.19800630825

Helvetica Chimica Acta

1980

DOI: 10.1002/hlca.19800630825

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Steroids and sex hormons. Part 264. Lewis acid catalyzed reversible [1,5]‐hydride shift in 3,19‐epoxy‐steroids

Georg Acklin¹,

Walter Graf²

Abstract: Summary 3p, 19-Epoxy-3 cr-methoxy-steroids (e.g.

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Cited by 3 publications

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ChemInform Abstract: STEROIDS AND SEX HORMONES. PART 264. LEWIS ACID CATALYZED REVERSIBLE (1,5)‐HYDRIDE SHIFT IN 3,19‐EPOXYSTEROIDS

Acklin¹,

Graf²

1981

Chemischer Informationsdienst

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Im Zusammenhang mit Untersuchungen über Partial‐ Synthesen von triterpenoiden Bitterstoffen, wie Limonin und Quassin, wird die Stabilität der inneren Acetalgruppe von Steroidepoxiden wie (I) gegenüber Lewis‐ Säuren getestet: (Ia) geht beim Behandeln mit BF3 ‐ Et2O bei Raumtemp. in Benzol ‐ unter reversibler, intramolekularer [1 ,5 ]‐Hydridverschiebung (von C‐1 9 ‐ C‐3) ‐ in das 19‐Oxo‐Derivat (IIa) über.

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ChemInform Abstract: STEROIDS AND SEX HORMONES. PART 264. LEWIS ACID CATALYZED REVERSIBLE (1,5)‐HYDRIDE SHIFT IN 3,19‐EPOXYSTEROIDS

Acklin¹,

Graf²

1981

Chemischer Informationsdienst

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Steroids and Sexhormones. Part 265. Limonin, Part VI. Synthesis of a model compound incorporating rings D and E of 14,15‐deepoxylimonin

Emmer

Graf

1981

Helvetica Chimica Acta

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Dedicated to ProfessorGeorge H. Biichi on the occasion of his 60ttl birthday (1 1. V. 81) SummaryStarting from the known formyl ketene thioacetal 6, model compound 11 was synthesized. The key intermediates, the epimeric furylmethanols 7a and 7b, were converted into the same dithioortholactone 8b (Scheme 1) and further elaborated into the model compound 11 (Scheme 2), a versatile compound in the synthesis of limonin (1). The acid catalyzed conversion of the epimers 7a and 7b into 8b may probably involve a hydride-transfer reaction with inversion of configuration at C(17) of alcohol 7a (Scheme 4, row b). Part 264 : see [ 1 a]. Limonin, Part V :see [lb]. Some exploratory experiments were performed by W. Lottenbach [Ic]. Present address ofthe senior author: c/o H u h AG, Chemische Fabrik, CH-9470 Buchs/SG. 0018-019X/81/5/1398-09%01 .OO/O 0 1981 Schweizerische Chemische Gesellschaft

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Rearrangements of some polycyclic hydroxy ketones in strong protic acids

Mills¹,

Watt²,

Whitworth³

1990

J. Chem. Soc., Perkin Trans. 2

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The polycyclic hydroxy ketones (1)-( 3) are unaffected by treatment with 1 mol dm-3 aqueous hydrochloric acid. Hydroxy ketone (5) is also stable to fluorosulphonic acid-antimony pentafluoride in liquid sulphur dioxide at 0°C. 'H and 13C NMR spectroscopy shows that (5) is protonated on both alcohol and carbonyl oxygens in this medium, and an activation energy, AG*, of 14.7 f 0.8 kcal mol-l, for geometric isomerism of the protonated carbonyl has been determined by dynamic NMR methods. The rate, k = 1.1 7 s-l (23.3 "C) of degenerate rearrangement of ( 5) by 1,4-hydride shift from alcohol methine to carbonyl carbon in trifluoromethanesulphonic acid in liquid sulphur dioxide solution was determined by spin-saturation transfer experiments. The primary kinetic isotope effect was 2.30 f 0.35. In trifluoromethanesulphonic acid, (5) also rearranges more slowly to (7) or (8). In strongly acidic media, hydroxy ketone (6) rearranges rapidly to a mixture of ( 9) and ( 10). The X-ray crystal structure of ( 10) has been determined. * For a discussion of the basicity of carbonyl and alcoholic oxygen see 'The Proton; Applications to Organic Chemistry,' ed. R. Stewart,

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Steroids and sex hormons. Part 264. Lewis acid catalyzed reversible [1,5]‐hydride shift in 3,19‐epoxy‐steroids

Abstract: Summary 3p, 19-Epoxy-3 cr-methoxy-steroids (e.g.

Cited by 3 publications

References 32 publications

ChemInform Abstract: STEROIDS AND SEX HORMONES. PART 264. LEWIS ACID CATALYZED REVERSIBLE (1,5)‐HYDRIDE SHIFT IN 3,19‐EPOXYSTEROIDS

ChemInform Abstract: STEROIDS AND SEX HORMONES. PART 264. LEWIS ACID CATALYZED REVERSIBLE (1,5)‐HYDRIDE SHIFT IN 3,19‐EPOXYSTEROIDS

Steroids and Sexhormones. Part 265. Limonin, Part VI. Synthesis of a model compound incorporating rings D and E of 14,15‐deepoxylimonin

Rearrangements of some polycyclic hydroxy ketones in strong protic acids

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