Photochemistry of nitroso compounds in solution. XV. Configuration and conformation of the enone oximes obtained from photoaddition of <i>N</i>-nitrosopiperidine to conjugated dienes

Chow, Yuan L.; Colón, Carlos; Chang, Dong Chil

doi:10.1139/v70-275

Cited by 10 publications

(6 citation statements)

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“…The definition of syt~-anri configuration follows the convention adapted in our previous publication (ref. 7). gave the same 1,4-adducts, 1, and the 4,l -adduct, 4, as that obtained in the addition to cis-pentadiene though both in lesser yields.…”

Section: P Hotoaddition P Rod~lctssupporting

confidence: 57%

“…This relation holds true for other types of oximes, for an intramolecular comparison and for an intermolecular comparison where syn-anti pairs are available (7,12,13). Secondly, the cis-trans isomerism of the double bond is decided by well-known spin coupling constant correlations (14) in which coupling constants for transprotons (1 1-17 Hz) are larger than that of cisprotons (6-12 Hz).…”

Section: P Hotoaddition P Rod~lctsmentioning

confidence: 98%

“…The adducts derived from photoaddition to acyclic dienes exhibited well-defined signals in most cases and provided a good deal of information with regard to the structure and stereochemistry. Taking together the data available from our previous (7,11) and present studies we have arrived at a few general rules that facilitate a decision on enone oxime structure.…”

Section: P Hotoaddition P Rod~lctsmentioning

confidence: 98%

“…For the sole 1,4-adduct (1 and 9) obtained in the photoaddition, the anti-configuration was assigned on steric grounds (1 1); the syn-configuration would cause strong crowding of the OH group with the olefinic protons (either in s-cis or s-trans arrangement) due to coplanarity within the conjugated system (10). The anti-configuration of the 4,ladduct 4 is indicated by the chemical shift of the aldoxime proton (He, T 2.3) which is correlated better to the corresponding proton of nnti-4-piperidino-2-butenal oxime (14, T 2.28) than to that of the syn-isomer (13, T 2.90) (7).…”

Section: P Hotoaddition P Rod~lctsmentioning

confidence: 99%

“…cyclic dienes (7). In this photoaddition, a number of questions arise regarding photoprocesses and addition processes (8).…”

Section: Introductionmentioning

confidence: 99%

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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: P Hotoaddition P Rod~lctssupporting

confidence: 57%

Section: P Hotoaddition P Rod~lctsmentioning

confidence: 98%

Section: P Hotoaddition P Rod~lctsmentioning

confidence: 98%

Section: P Hotoaddition P Rod~lctsmentioning

confidence: 99%

“…cyclic dienes (7). In this photoaddition, a number of questions arise regarding photoprocesses and addition processes (8).…”

Section: Introductionmentioning

confidence: 99%

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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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Umpolung der Reaktivität von Aminen. Nucleophile α‐sek.‐Aminoalkylierung über metallierte Nitrosamine

Seebàch¹,

Enders²

1975

Angewandte Chemie

124

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Es gibt prinzipiell zwei Arten von Heteroatomen in organischen Molekiilen: Die einen machen das mit ihnen verbundene Kohlenstoffatom zu einem elektrophilen, die anderen zu einem nucleophilen Zentrum. Die Entwicklung von Methoden zum Uberwechseln zwischen den beiden darauf beruhenden Kategorien von Reagentien ist eine wichtige Aufgabe der modernen organischen Synthese. Moglichkeiten dieser Umpolung der Reaktivitat funktioneller Gruppen werden am Beispiel der Amine diskutiert. Eine Methode zur Herstellung von maskierten a-sek.-Aminocarbanionen besteht darin, daD man das sekundare Amin nitrosiert, das entstandene Nitrosamin in a-Stellung zum Stickstoff metalliert, mit Elektrophilen umsetzt und entnitrosiert. Fur jeden dieser Schritte wird eine Anzahl von Beispielen gegeben, die die groBe Anwendungsbreite der synthetischen Gesamtoperation (elektrophile Substitution am a-C-Atom des sekundaren Amins) belegen. Erste Anwendungen und ein Verfahren zur Umgehung des Hantierens von Nitrosaminen werden vorgestellt, und zum SchluD wird die Bedeutung der Nitrosamine fur die Carcinogenese-und Mutageneseforschung kurz erortert.

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Umpolung of Amine Reactivity. Nucleophilic α‐(Secondary Amino)‐alkylation via Metalated Nitrosamines

Seebàch¹,

Enders²

1975

Angew. Chem. Int. Ed. Engl.

207

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There are basically two kinds of hetero atoms in organic molecules: one kind confers electrophilic character upon the carbon atom to which it is bound, and the other kind turns it into a nucleophilic site. The development of methods permitting transitions between the two resulting categories of reagents has become an important task of modern organic synthesis. The scope of such umpolung of the reactivity of functional groups is discussed for the case of amines as an example. A method of preparing masked u-secondary amino carbanions consists in nitrosation of the secondary amine, followed by metalation of the resulting nitrosamine CL to the nitrogen, reaction with electrophiles, and subsequent denitrosation. Many examples are given for each of these steps which illustrate the wide scope of the overall synthetic operation (electrophilic substitution at the a-C atom of the secondary amine). Preliminary applications and a method for avoiding the handling of nitrosamines are presented, and the report concludes with a brief account of the significance of nitrosamines in the study of carcinogenesis and mutagenesis. Table 2. Examples for umpolung of carbonyl compounds and amines. Newly formed bonds are shown in bold print. Attack Reagent Equivalent Product type Ref.

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Photochemistry of nitroso compounds in solution. XV. Configuration and conformation of the enone oximes obtained from photoaddition of N-nitrosopiperidine to conjugated dienes

Cited by 10 publications

References 10 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

Umpolung der Reaktivität von Aminen. Nucleophile α‐sek.‐Aminoalkylierung über metallierte Nitrosamine

Umpolung of Amine Reactivity. Nucleophilic α‐(Secondary Amino)‐alkylation via Metalated Nitrosamines

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