Beckmann Fragmentation and Rearrangement. Part VI thian‐3‐one oximes. Fragmentation reactions no. 26

Grob, C. A.; Ide, Junya

doi:10.1002/hlca.19740570832

Cited by 11 publications

(1 citation statement)

References 23 publications

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“…Subsequently, the proposed distance relation of Wolkowski was employed in assigning configuration to pairs of oximes. In one paper the assignment on this basis (4) turned out to be in error (5), while a second utilization of the dependence on distance from oxygen actually gave the correct assignment as it was unambiguously confirmed by subsequent Beckmann rearrangements (6). Interestingly, a comparable correlation).…”

mentioning

confidence: 82%

The use of shift reagents and ¹³C nuclear magnetic resonance for assignment of stereochemistry to oximes

Fraser¹,

Capoor²,

Bovenkamp³

et al. 1983

Can. J. Chem.

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The effects of the shift reagents Eu(dpm), and Eu(fod), on the 'H and "C nmr spectra of twelve oximes of diverse structure were examined. The proton data show that the use of proton shifts to assign oxime stereochemistry, as has been done in the past, is unreliable. In contrast, Eu(dpm), causes LIS values for the "C signals of a carbons which are strongly dependent on stereochemistry. Signals for all a carbons anti to the oxime oxygen experience large downfield shifts while all syrl carbons are either unaffected or shifted upfield. Thus the effects of Eu(dpm), on these I7C signals provides an unambiguous method of configurational assignment to oximes. The effects of Eu(fod),, though similar to Eu(dpm),, were less consistent and thus less promising for making configurational assignments.ROBERT R. FRASER, RAJ CAPOOR, JOHN W. BOVENKAMP, BENOIT V. LACROIX et JACK PAGOTTO. Can. J. Chem. 61,2616Chem. 61, (1984.On a CtudiC les effets des rtactifs de contact Eu(dpm), et Eu(fod), sur les spectres de rmn du 'H et du I3C de douze oximes ayant diverses structures. Les donnCes de la rmn du proton rCvklent que I'utilisation des rkactifs de contact pour attribuer la stCrCochimie d'oximes n'est pas rigoureuse. Le Eu(dpm), au contraire provoque des dtplacements des signaux du "C des carbones en position a qui dtpendent beaucoup de la stCrCochimie. Les signaux de tous les carbones a en position anti par rapport 2 l'oxime-oxygkne subissent de forts dCplacements vers les champs faibles tandis que tous les carbones en position syn ou bien ne bougent pas ou alors se dtplacent vers les champs forts. Ainsi I'effet du Eu(dpm), sur ces signaux du "C foumit une mCthode non equivoque d'attribution de configuration des oximes. Les effets du Eu(fod),, quoiqu'identiques 2 ceux du E~( d p m )~, sont moins cohtrents et par constquent peu sDrs pour faire des attributions de configuration.[Traduit par le journal]The effect of the addition of the shift reagent, E u ( d~m ) ,~ on the proton spectra of oximes has been the subject of some controversy and of considerable misunderstanding. The first study by Wolkowski (1) described the observation of a dependence of the observed downfield shifts on the proton to oxime oxygen distance. In the same year, a paper by Berlin and Rengaraju (2) described a study of the effect of adding Eu(dpm), to a mixture of E and Z 2-butanone oximes. The conclusion of this paper, based on the observation of larger lanthanide induced shifts (LIS values) for all of the protons in the Z isomer, was that complexation occurred at the nitrogen atom. Concurrently, a third paper by Tronchet et al. (3) described a study of LIS values for pairs of isomeric aldoximes. For this class of oximes the Z isomers were also observed to give much larger downfield shifts, indicative of coordination at nitrogen. Subsequently, the proposed distance relation of Wolkowski was employed in assigning configuration to pairs of oximes. In one paper the assignment on this basis (4) turned out to be in error (5), while a second utilization of the depe...

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mentioning

confidence: 82%

The use of shift reagents and ¹³C nuclear magnetic resonance for assignment of stereochemistry to oximes

Fraser¹,

Capoor²,

Bovenkamp³

et al. 1983

Can. J. Chem.

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TheBeckmann Reactions: Rearrangements, Elimination–Additions, Fragmentations, and Rearrangement–Cyclizations

Gawley

1988

Organic Reactions

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The Beckmann rearrangement, the acid‐mediated isomerization of oximes to amides, was discovered by Beckmann in 1886. As one of the oldest and most familiar transformations in organic chemistry, it has been reviewed several times. What has become known as the Beckmann fragmentation was in fact first observed by Wallach in 1889 but was not developed extensively until the 1960s. It has been referred to by several names over the years and has also been reviewed. The rearrangement cyclization is the intramolecular cyclization of a nitrilium ion generated by Beckmann rearrangement from an oxime. Within the context of an aromatic terminator, the process was first reported by Goldschmidt in 1895. Wallach reported the first case of an aliphatic terminator in 1901, although the reported structure was incorrect, and Perkin was apparently the first to observe a heteroatom terminator, but he also reported an incorrect structure. The process has been exploited only quite recently. This chapter is an update of these reactions, last reviewed in this series in 1960. Not covered are transformations that have been labeled Beckmann‐type reactions but are mechanistically unrelated. The most prominent of these is the so‐called photochemical Beckmann rearrangement, first observed by De Mayo in 1963 and discussed in a review several years ago. Worthy of mention, however, is the fact that many oximes that suffer fragmentation under acidic conditions undergo rearrangement when photolyzed. Throughout this chapter, the ( E ) and ( Z ) nomenclature is used to describe oxime geometry.

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Beckmann Rearrangement and Beckmann Fragmentation

2010

Comprehensive Organic Name Reactions and Reagents

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The rearrangement of an oxime to its corresponding amide in the presence of an acid and is generally known as the Beckmann rearrangement. The oxime is also formed by the reaction of a ketone with hydroxylamine. The conversion of cyclohexanone oxime into e‐caprolactam is known to be an important component for the fabrication of nylon 6. The Beckmann rearrangement of oxime derivatives proceeds stereospecifically, and the stereo‐configuration of the migrating group is retained. This rearrangement has been applied to the construction of a variety of nitrogen‐containing compounds. Certain oximes, those having a quarternary carbon anti to the hydroxyl, have been reported to undergo the rearrangement to form nitriles instead of amides. This type of transformation is called the Beckmann fragmentation, which has been used in modification of steroids. Other oximes, such as the bridged bicyclic ketoximes and oximes with an electron‐donating substituent at the α‐carbon, also undergo fragmentation.

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Beckmann Fragmentation and Rearrangement. Part VI thian‐3‐one oximes. Fragmentation reactions no. 26

Cited by 11 publications

References 23 publications

The use of shift reagents and ¹³C nuclear magnetic resonance for assignment of stereochemistry to oximes

The use of shift reagents and ¹³C nuclear magnetic resonance for assignment of stereochemistry to oximes

TheBeckmann Reactions: Rearrangements, Elimination–Additions, Fragmentations, and Rearrangement–Cyclizations

Beckmann Rearrangement and Beckmann Fragmentation

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Beckmann Fragmentation and Rearrangement. Part VI thian‐3‐one oximes. Fragmentation reactions no. 26

Cited by 11 publications

References 23 publications

The use of shift reagents and 13C nuclear magnetic resonance for assignment of stereochemistry to oximes

The use of shift reagents and 13C nuclear magnetic resonance for assignment of stereochemistry to oximes

TheBeckmann Reactions: Rearrangements, Elimination–Additions, Fragmentations, and Rearrangement–Cyclizations

Beckmann Rearrangement and Beckmann Fragmentation

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The use of shift reagents and ¹³C nuclear magnetic resonance for assignment of stereochemistry to oximes

The use of shift reagents and ¹³C nuclear magnetic resonance for assignment of stereochemistry to oximes