Rearrangements in Carbanions

Hunter, D. H.; Stothers, J. B.; Warnhoff, E. W.

doi:10.1016/b978-0-12-481301-4.50012-7

Cited by 24 publications

(18 citation statements)

References 193 publications

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“…Preferential exchange at the exo-methyl group has been observed in several polycyclic systems (2) and evidence supporting the intermediacy of a cyclopropoxide in this process has been presented for a number of bicyclic ketones (17). Exchange at C-3 is stereospecific with deuterium only in the exo orientation.…”

Section: Hid Exchange Experimentsmentioning

confidence: 96%

“…These data established that the cleavage of 3 proceeded with 95 + 3% retention of configuration. Examinations of several other substituted cyclobutanols have also revealed high stereoselectivities favoring retention (2). Strong evidence to support the formation of a cyclic y-enolate in camphor, as had been proposed to account for HID exchange at the syn-methyl carbon (4), has been provided by the preparation of 4, homoketonization of which, in a deuterated medium, gave 8-deuteriocamphor exclusively (10).…”

Section: Introductionmentioning

confidence: 96%

“…In all cases, exo-6-deuterionorcamphor was the major product (>95%), showing that inversion of configuration is strongly favored. Subsequently, examinations of several other p-enolates have demonstrated that p-enolate cleavages tend to be highly stereoselective, generally proceeding with inversion although a number of highly strained polycyclic systems exhibit retention of configuration (2). Homoketonization of several y-enolates has also received attention.…”

Section: Introductionmentioning

confidence: 99%

“…Following the original discovery that, under strongly basic conditions, a ketonic carbonyl group can activate proton abstraction from carbons more than one bond removed (I), many examples involving both acyclic and polycyclic monoketones have been described (2). Most of these cases concern p-enolization, i.e., proton abstraction from P-carbons.…”

Section: Introductionmentioning

confidence: 99%

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Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a ²Hmr study of H/D exchange in tricyclic ketones

Cheng¹,

Ghosh²,

Stothers³

1984

Can. J. Chem.

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. J. Chem. 62, 1385Chem. 62, (1984.The effect of strongly basic conditions (t-BuOL/t-BuOH/I85"C) on the exo and endo isomers of 7,7-dimethyltricyclo[3.2. I .02."]octan-6-one has been examined. While the exo isomer is stable, the endo isomer readily rearranges to 4,4-dimethyltricyclo[3.3.0.0'.H]octan-3-one (6) which subsequently undergoes reduction of the three-mcrnbered ring. 'The initial transformation is one of very few examples of y-enolate rearrangement. Experiments in tert-butyl alcohol-0-d, were carried out to establish the several sites of deuterium incorporation in the initial ketones and in 6 using '~m r . These results reveal the stereochemistry of y-enolate formation and cleavage as well as the stercoselectivities and relative rates of the exchange processes.A. K. CHENG, ASHIM K. GHOSH et J. B. STOTHERS. Can. J. Chem. 62, 1385 (1984.On a CtudiC I'effet de conditions fortement basiques (t-BuO-/t-BuOH/l85"C) sur les isomeres exo et endo de la dimkthyl-7,7 tricyclo

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Section: Hid Exchange Experimentsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a ²Hmr study of H/D exchange in tricyclic ketones

Cheng¹,

Ghosh²,

Stothers³

1984

Can. J. Chem.

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“…Although there are two modes of ring opening for the p-enolate formed from 7 0 , shown as a and b in 10, the cyclopropoxide cIeavage is apparently regiospecific. Since cleavage a and b both lead to secondary carbanions, the exclusive formation of 8a is an illustration of thermodynamic control of homoketonization, a feature which has been recognizecl for some years (9) and indicates that 8a is more stable than 11. The second aspect, stereoselectivity of protonation (deuteriation) at the carbanionic site, required additional evidence for its clarification.…”

Section: I O'']octan-4-one In Very Good Yieldmentioning

confidence: 99%

A serendipitous, high yield conversion of norbornenone to tricyclo[3.2.1.0^2,7]octan-4-one

Ragauskas¹,

Stothers²

1983

Can. J. Chem.

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A semiempirical study on the ring-opening process for the cyclopropanone, 2,2-dimethylcyclopropanone,trans-2,3-di-tert-butylcyclopropanone, and spiro(bicyclo[2.2.1]heptane-2.1?-cyclopropan)-2?-one systems in solution

Castillo

Andrés

Moliner

et al. 1997

Int. J. Quant. Chem.

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ABSTRACT:The molecular mechanisms for the ring openings of cyclopropanone, 2,2-dimethylcyclopropanone, trans-2,3-di-tert-butylcyclopropanone, and Ž w x X . X spiro bicyclo 2.2.1 heptane-2.1-cyclopropan -2 -one systems were studied at the PM3 semiempirical level in the gas phase and including solvent effects. The behavior of the solvent polarity was considered by using the SCRF polarizable continuum method. Six solvents were selected: hexane, ether, tetrahydrofuran, pyridine, acetone, and acetonitrile. An extensive exploration of the potential energy surface using analytical gradient techniques allows the characterization of stationary points associated to the stereomutation conversion. Along a disrotatory ring-opening mechanism, cyclopropanone, 2,2-dimethylcyclopropanone and trans-2,3-di-tert-butylcyclopropanone are intraconverted Ž w x X via an oxyallyl intermediate. The epimeric forms of the spiro bicyclo 2.2.1 heptane-2.1-.X cyclopropan -2 -one intraconvert along two competitive pathways correspond to two-step processes by a disrotatory ring-opening mechanism. Two oxyallyl intermediates and four transition structures were obtained and the corresponding transition vectors are associated to the carbon᎐carbon bond-breaking process and the dihedral angle measuring the conrotatory movement of the plane defined by the three carbon atoms of the cyclopropanone ring. The oxyallyl intermediates and the transition structures for the four model systems present similar structures and energies and they are located on a ratherCorrespondence to: R. Castillo.

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Rearrangements in Carbanions

Cited by 24 publications

References 193 publications

Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a ²Hmr study of H/D exchange in tricyclic ketones

Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a ²Hmr study of H/D exchange in tricyclic ketones

A serendipitous, high yield conversion of norbornenone to tricyclo[3.2.1.0^2,7]octan-4-one

A semiempirical study on the ring-opening process for the cyclopropanone, 2,2-dimethylcyclopropanone,trans-2,3-di-tert-butylcyclopropanone, and spiro(bicyclo[2.2.1]heptane-2.1?-cyclopropan)-2?-one systems in solution

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Rearrangements in Carbanions

Cited by 24 publications

References 193 publications

Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a 2Hmr study of H/D exchange in tricyclic ketones

Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a 2Hmr study of H/D exchange in tricyclic ketones

A serendipitous, high yield conversion of norbornenone to tricyclo[3.2.1.02,7]octan-4-one

A semiempirical study on the ring-opening process for the cyclopropanone, 2,2-dimethylcyclopropanone,trans-2,3-di-tert-butylcyclopropanone, and spiro(bicyclo[2.2.1]heptane-2.1?-cyclopropan)-2?-one systems in solution

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Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a ²Hmr study of H/D exchange in tricyclic ketones

Nuclear magnetic resonance studies. XL. Tricyclooctanone rearrangement, [3.2.1.0] → [3.3.0.0], via γ-enolization and a ²Hmr study of H/D exchange in tricyclic ketones

A serendipitous, high yield conversion of norbornenone to tricyclo[3.2.1.0^2,7]octan-4-one