Fragmentierung von α‐Aminoketoximen. III. Teil Mono‐ und bicyclische Verbindungen. Fragmentierungs‐Reaktionen. 6 Mitteilung

Grob, C. A.; Fischer, H. P.; Link, Helmut; Renk, E.

doi:10.1002/hlca.19630460415

Cited by 58 publications

(17 citation statements)

References 36 publications

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“…In order to prove the second conclusion, advantage was taken that these 1,2-adducts undergo a facile Beckmann cleavage reaction aided by the lone pair electron of the piperidine ring as shown in 16 (Scheme 2) (18,19). The cleavage of the tosylates 7,8,10, or 11 under mild conditions gave only trans-crotononitrile as shown by v.p.c.…”

Section: Stereocl~enzical Course Of the Photoa~iditionmentioning

confidence: 99%

Photoreactions of Nitroso Compounds in Solution. XXII. Stereochemical Consequences of the Photoaddition of N-Nitrosopiperidine to Conjugated Acyclic Dienes: a Nuclear Magnetic Resonance Study of Enone Oximes

Chow¹,

Colón²,

Quon³

et al. 1972

Can. J. Chem.

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In the presence of an acid, photoexcited N-nitrosopiperidine adds to conjugated acyclic 1,3-dienes to give the 1,4-adducts as the major product in addition to 1,2-adducts. In the photoaddition to IJpentadienes the reverse 4,l-adduct and 4,3-adducts are also identified. These results suggest that a singlet photoexcited N-nitrosopiperidine-acid complex rapidly decays to piperidinium radical which irreversibly attacks the dienes as the first step, followed by either a short propagation step or a termination step to give C-nitroso compounds. The C-nitroso compounds are rapidly removed by irreversible tautomerization to the final oximes. The reactivity of the piperidinium radical toward conjugated double bonds decreases in the order of RCH=CH, > cis-RCH=CHR > tratzs-RCH=CHR. This mechanism is in accord with the following stereochemical results. Firstly, the newly-formed double bond in the 1,4-adduct (or the adduct of the reverse orientation) is exclusively trans-oriented. Secondly, the remaining double bonds in the 1,2-adducts maintain their original stereochemistry.The stereochemistry of the photoadducts, enone oximes 1-11, was determined by means of n.m.r. spectroscopy. From the correlation of the n.m.r. chemical shifts of these enone oximes it has been shown that (i) the a-olefinic proton generally resonates at a lower field than the P-olefinic proton (with one exception) and (ii) in changing from CDCI, to an aromatic solvent the a-olefinic proton and the a'-alkyl protons are deshielded by 0.3-0.05 p.p.m. while the 11-olefinic proton is shifted only slightly either to a higher or a lower field. It is observed that the order of the chemical shifts of the olefinic protons and the aromatic solvent effects on the chemical shifts in these enone oximes are both opposite to those observed in enone systems.En presence d'un acide, le N-nitrosopiperidine photoexcite reagit avec les 1,3-dienes acycliques conjugues pour donner lieu aux derives-1.4 comme produits principaux, de m&me qu'aux derives-1,2. Durant la photoaddition aux 1,3-pentadienes, on a aussi observe la formation des derives-4.1 et 4,3. Ces resultats suggerent qu'un complexe singulet photoexcite de N-nitrosopiperidine et d'acide se dissocie rapidement en radical piperidinium qui attaque de f a~o n irreversible les dienes d'abord, pour ensuite entreprendre une courte &ape de propagation ou de terminaison pour donner les composts C-nitroso. Les composes C-nitroso sont rapidement elimines par tautomerisation irreversible pour donner les oximes, qui sont les produits finaux. La reactivitt du radical piperidinium pour les doubles liaisons conjuguees se manifeste dans I'ordre decroissant suivant:RCH=CH, > cis-RCH=CHR > trans-RCH=CHR. Ce mecanisme est en accord avec les resultats stereochimiques suivants. Premierement, la double liaison nouvellement formee dans le derive-1,4 (ou le derive d'orientation opposee) est orient6 exclusivement de maniere trans. Deuxiemement, les autres doubles liaisons des derives-1,2 conservent leur stereochimie originale.On a determine par ...

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Section: Stereocl~enzical Course Of the Photoa~iditionmentioning

confidence: 99%

Photoreactions of Nitroso Compounds in Solution. XXII. Stereochemical Consequences of the Photoaddition of N-Nitrosopiperidine to Conjugated Acyclic Dienes: a Nuclear Magnetic Resonance Study of Enone Oximes

Chow¹,

Colón²,

Quon³

et al. 1972

Can. J. Chem.

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“…Aus dem anfallenden Gemisch liess sich in 60-proz. Ausbeute einheitliches, kristallisiertes Podophyllotoxin-@-n-glucosid (111) gewinnen, das rnit einem authentischen Praparat aus Podo$hyllurn ernodi [2] iibereinstimmte. Als Nebenprodulit isolierten wir ca.…”

Section: Synthese Von T E T R a -O -A C E T Y L -P O D O P H Y L L O unclassified

“…15% Podophyllinsaure-methylester-1-@-u-glucosid (IV) und ca. 10% Pikropodophyllin-@-D-glucosid [2] [lo].…”

Section: Synthese Von T E T R a -O -A C E T Y L -P O D O P H Y L L O mentioning

confidence: 99%

Abspaltung von Acyl‐Schutzgruppen bei alkaliempfindlichen Glucosiden. – Synthese von Podophyllotoxin‐β‐D‐glucosid. 20. Mitteilung über mitosehemmende Naturstoffe [1]

Kühn

Wartburg

1968

Helvetica Chimica Acta

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The synthesis of podophyllotoxin‐β‐D‐glucoside (III), an antimitotic lignan compound isolated from Podophyllum species, is reported. Reaction of podophyllotoxin (I) with tetra‐O‐acetyl‐α‐D‐glucopyranosyl bromide in acetonitrile in the presence of Hg(CN)2 yields tetra‐O‐acetyl‐podophyllotoxin‐α‐D‐glucoside (II), which is converted into podophyllotoxin‐β‐D‐glucoside (III) by ZnCl2‐catalysed methanolysis. This transesterification is an advantageous method for the preparation of glycosides, sensitive to base and acid, from their corresponding acetyl derivatives. Scope and conditions of the reaction are discussed.

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“…C 62,31 H 9,37 N 18,13% N-(4-ChinucZidinyl)-methylcavbaminat ( 2 4 ) . 620 ing (15,6 mMol) NaOH und 0,20 ml(3,90 mMol) Brom in 20 ml Methanol wurden bei 0" mit 0,5 ml Wasser und 400 mg (2,6 mMol) …”

Section: -unclassified

BECKMANN‐Umlagerung und Fragmentierung. II. Teil. Versuche zur 7‐Zentren‐Fragmentierung von γ‐Aminoketoximen. Fragmentierungsreaktionen, 19. Mitteilung

Fischer

Grob

1968

Helvetica Chimica Acta

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Surnmary. The occurrence of so-called synchronous 7-centre-fragmentation has been excluded for y-amino-ketoxime dcrivatives N-C--C-C-C=K-X.Fragmentation may occur, however, by another route.Reaction rates of the p-toluenesulfonates of (4-quinuclidinyl)-mcthyl-ketoxime (10 b) and (3,f-tropanyl)-mcthyl-ketoxime (14 b) in 80% ethanol and thc resulting products have been determined. Whereas the latter y-aminoketoxime underwent quantitative RECKMANN rearrangement to 3,f-acetylaminotropane (29), the former yielded 3% fragmentation products besides rearranged 4-acetylamino-quinuclidine (13).A kinetic study reveals that both 10b and 14b react via the rearranged nitriliuni ions 12a and l b a , respectively. In the case of the N-(4-quinuclidinyl)-acetonitrilium ion (12a) 5-centre-fragmentation competes with hydration to the amidc 13.Die bisherige Untersuchung der Keaktivitat von cl-di-und -tri-substituierten Ketoxim-Derivaten 1 (z. B. R = t-butyl) hat ergeben, dass die RwxhIANN-Umlagerung zu Amiden 3 von der BECKMAXN-Fragmentierung zu Nitrilen 4 und dem CarbeniumIon 5 (R+ z.R. (CH,),C+) begleitet wird, und dass das Nitrilium-Ion 2 eine gemeinsame Vorstufe darstellt [I].

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Fragmentierung von α‐Aminoketoximen. III. Teil Mono‐ und bicyclische Verbindungen. Fragmentierungs‐Reaktionen. 6 Mitteilung

Cited by 58 publications

References 36 publications

Photoreactions of Nitroso Compounds in Solution. XXII. Stereochemical Consequences of the Photoaddition of N-Nitrosopiperidine to Conjugated Acyclic Dienes: a Nuclear Magnetic Resonance Study of Enone Oximes

Photoreactions of Nitroso Compounds in Solution. XXII. Stereochemical Consequences of the Photoaddition of N-Nitrosopiperidine to Conjugated Acyclic Dienes: a Nuclear Magnetic Resonance Study of Enone Oximes

Abspaltung von Acyl‐Schutzgruppen bei alkaliempfindlichen Glucosiden. – Synthese von Podophyllotoxin‐β‐D‐glucosid. 20. Mitteilung über mitosehemmende Naturstoffe [1]

BECKMANN‐Umlagerung und Fragmentierung. II. Teil. Versuche zur 7‐Zentren‐Fragmentierung von γ‐Aminoketoximen. Fragmentierungsreaktionen, 19. Mitteilung

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