B<scp>ECKMANN</scp>‐Umlagerung und Fragmentierung. 1. Teil. Mechanismus sowie Nachweis der Zwischenstufen Fragmentierungsreaktionen. 7. Mitteilung

Grob, C. A.; Fischer, H. P.; Raudenbusch, W.; Zergenyi, J.

doi:10.1002/hlca.19640470411

Cited by 79 publications

(25 citation statements)

References 37 publications

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“…EtOH gave two types of products and that the percentage of the fragmentation product (F/(F + R)) increased when the R 1 group became better stabilized as a cation (R 1 ¼ CHPh 2 > t-Bu > i-Pr). 16 On the other hand, the reactivity was found not to follow the same order (R 1 ¼ t-Bu > i-Pr > Ph > Et > CHPh 2 ). Thus, the product selectivity and the reactivity were controlled in different steps.…”

Section: Introductionmentioning

confidence: 95%

Dynamic path bifurcation for the Beckmann reaction: observation and implication

et al. 2010

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The reaction of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles instead of amides when the cations have reasonable stability. The reactions of oxime derivatives of 1-substituted-phenyl-2-propanones and 3-substituted-phenyl-2-butanones in aqueous solvents gave both rearrangement and fragmentation products, the ratio of which was dependent on substituents. Transition state (TS) optimizations and intrinsic reaction coordinate (IRC) calculations for the reaction of 1-phenyl-2-propanone oximes showed that there is a single TS for each substituted compound. The IRC path from the TS either led to a rearrangement product or a fragmentation product depending on the substituent; the IRC path changes from rearrangement to fragmentation when substituent X becomes more electron donating. Ab initio dynamics simulations were found to follow the IRC path for X ¼ p-NH 2 and p-MeO giving fragmentation products, and almost so for X ¼ p-NO 2 giving the rearrangement products. However, in a borderline case where X is less donating than p-MeO or less withdrawing than p-NO 2 , the trajectories did not follow the minimum energy path on the potential energy surface, but gave both rearrangement and fragmentation products directly from the single TS. This is a novel example of path bifurcation for a closed shell anionic reaction. It was concluded that a reactivity-selectivity argument based on the traditional TS theory may not always be applicable even to a well-known textbook organic reaction.

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Section: Introductionmentioning

confidence: 95%

Dynamic path bifurcation for the Beckmann reaction: observation and implication

et al. 2010

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“…In Fallen, in welchen die Reaktionsgeschwindigkeit (RG) gemessen wurde, zeigte sich, dass die a-Aminogruppe eine enorme Erhohung der Ionisationsgeschwindigkeit bewirkt im Vergleich zu sterisch gleichwertigen, d. h. homomorphen, Ketoximen 2 ohne a-N-Atom. Da letztere ausschliesslich e h e BECKMANN-Umlagerung iiber Nitrilium-Ionen 3 erleiden [5], liefert der elektrofuge Austritt des Imonium-Ions die treibende Kraft fur die sog. synchrone Fragmentierung.…”

Section: Fragmentierung Von A-aminoketoximen IV Teil Der Einfluss Sunclassified

“…-N-Methyl-2-cyano-pifieridin (17b). 5 [N-iMethyZpyrrolidinyZ-(2)]-~henyZ-ketoxzm-ace~ut (13 b ) , vgl. [19].…”

Section: Experimenteller Teilmentioning

confidence: 99%

Fragmentierung von α‐Aminoketoximen. IV. Teil Der Einfluss sterischer. Faktoren Fragmentierungsreaktion, 17. Mitteilung

Grob

Sieber

1967

Helvetica Chimica Acta

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(N‐Methyl‐2‐piperidyl)phenyl ketoxime acetate(10b) and (N‐methyl‐2‐pyrrolidinyl)‐phenyl ketoxime acetate (13b) undergo quantitative fragmentation in 80% ethanol to yield benzonitrile and the cyclic imonium salts 11 and 14. Their reaction rates are approx. 107 and 108, respectively, as high as those calculated for the homomorphous compounds, viz. 2‐methylcyclohexylphenyl ketoxime acetate (12b) and 2‐methylcyclopentylphenyl ketoxime acetate (15b), which undergo quantitative Beckmann rearrangement. Synchronous fragmentation therefore provides a very large driving force for ionisation, even when the stereo‐electronically suitable conformation is not the prevalent one, as with 10b.

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“…27, 859 (1965), durch. [2] Der Verbindung ( 3 ) liegt das 1,3-Diphenyl-2H-inden zugrunde, dessen 2.2-Dimethylderivat K. Alder u. M . Fremery, Tetrahedron 14, 190 (1961).…”

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Ketenimine durch Beckmann‐Umlagerung

Hünig

Rehder

1968

Angewandte Chemie

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BECKMANN‐Umlagerung und Fragmentierung. 1. Teil. Mechanismus sowie Nachweis der Zwischenstufen Fragmentierungsreaktionen. 7. Mitteilung

Cited by 79 publications

References 37 publications

Dynamic path bifurcation for the Beckmann reaction: observation and implication

Dynamic path bifurcation for the Beckmann reaction: observation and implication

Fragmentierung von α‐Aminoketoximen. IV. Teil Der Einfluss sterischer. Faktoren Fragmentierungsreaktion, 17. Mitteilung

Ketenimine durch Beckmann‐Umlagerung

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