Geometrical isomerism in divalent-carbon intermediates

Roth, Heinz D.; Hutton, R. S.

doi:10.1016/s0040-4020(01)96397-5

Cited by 28 publications

(41 citation statements)

References 61 publications

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“…Such a structure, although not common, has been observed for dicyanomethylene [39]. Ab initio molecular should favour the bent structure, in agreement with Roth's findings [28] for bis(carbomethoxy)methylene 5 (R=OMe), Table II.…”

Section: = Os Nrsupporting

confidence: 87%

“…Only one thioxocarbene and a few closely related iminocarbene triplets have been detected by ESR to date, The existence of geometric isomers in triplet carbenes, initially observed in naphthylmethylenes by Trozzolo et al [41], has been extensively studied and recently reviewed by Roth and coworkers [28]. Here we will only present the essential principles underlying the assignment of the two sets of signals to each individual isomer, on the basis of Roth's pioneering work.…”

Section: = Os Nrmentioning

confidence: 96%

See 1 more Smart Citation

Detection of keto-, thioxo- and iminocarbenes and the quintet state triplet-triplet ketocarbene radical pairs

Torres

Safarik

Murai

et al. 1986

Reviews of Chemical Intermediates

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Section: = Os Nrsupporting

confidence: 87%

Section: = Os Nrmentioning

confidence: 96%

Detection of keto-, thioxo- and iminocarbenes and the quintet state triplet-triplet ketocarbene radical pairs

Torres

Safarik

Murai

et al. 1986

Reviews of Chemical Intermediates

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“…[145,146] Assignments were based on a point spin model which predicts D s-E Յ D s-Z . [149] Better alignment of the z-axis with the r vector of the carbonyl group, as in s-E-3 51, enhances the spin density on the carbonyl oxygen and lowers D (Scheme 25). Interaction of R 1 and R 2 leads to more distortion from planarity for s-E-3 51 than for s-Z-3 51, hence E s-E Ն E s-Z .…”

Section: Matrix Isolationmentioning

confidence: 99%

“…However, the D value of the cyclic s-E,s-E-constrained analogue 156 is smaller than any of the D values obtained for 157. [149] Therefore, it was concluded that only two conformers of 157 in different matrix sites were present. …”

Section: Matrix Isolationmentioning

confidence: 99%

100 Years of the Wolff Rearrangement

2002

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The conversion of α‐diazo ketones into ketenes, and products derived therefrom, was discovered by Wolff in 1902. Major applications of the Wolff rearrangement, such as the Arndt−Eistert reaction (homologation of carboxylic acids) and the ring contraction of cyclic ketones, have been with us for some while. Nevertheless, substantial progress has been made recently. The reaction mechanism has been explored by means of matrix isolation, time‐resolved spectroscopy, and computation. Full retention of configuration of the migrating group has been established by using enantioselective chromatography. The Arndt−Eistert reaction has witnessed a renaissance in the field of natural products, in particular β‐amino acids and β‐peptides. Ring‐contracting Wolff rearrangements and ketene cycloadditions have been applied in syntheses of increasingly complex, biologically active target molecules. These accomplishments, as well as unsolved problems, are addressed in the present review. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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“…In addition, 2-NPC in this glassy matrix at 77 K can exist in two different conformations, syn and anti, which have different zero-field splitting (ZFS) parameters in the To ground state. Such a conformational isomerism was first observed in EPR experiments for 1-and 2-naphthylcarbenes (13) and the measured D values were assigned to specific conformers on the basis of calculations involving the relationship established between the ZFS parameters D and n spin densities in the frame of the point-spin model (14,15).…”

mentioning

confidence: 92%

Conformational dependence of electronic spectra and zero-field splitting parameters in 2-naphthylphenylcarbene

Parisel¹,

Berthier²,

Migirdicyan³

1995

Can. J. Chem.

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Quantum mechanical calculations using ab initio and semi-empirical methods have been camed out for elucidating the electronic structure and geometry of 2-naphthylphenylcarbene conformers. The Zlcis conformer has the lowest ground state triplet energy, the lowest triplet-triplet (To-TI) transition energy, as well as the largest zero-field splitting parameter D. A clear-cut relationship between the D value and the geometry is pointed out.Key words: carbenes, conformational isomerism, triplet-triplet transitions, CS-INDOJCI calculations, ZFS D parameters.Resume : Dans le but dlCtudier la structure Clectronique et la gComCtrie du 2-naphtylphCnyle carbbne, des calculs de chimie quantique (ab initio et semi-empiriques) ont Ct C rCalisCs sur diffkrents conformbres de ce carbttne. Le calcul montre que c'est le conformkre Z k i s qui prksente 1'Cnergie minimale dans son Ctat triplet fondamental, 1'Cnergie de transition triplet-triplet (To-T,) la plus faible ainsi que la valeur la plus ClevCe du paramtttre D de sCparation des sous-niveaux triplets en champ nul. Une relation simple reliant D et la gComCtrie est mise en Cvidence.

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Geometrical isomerism in divalent-carbon intermediates

Cited by 28 publications

References 61 publications

Detection of keto-, thioxo- and iminocarbenes and the quintet state triplet-triplet ketocarbene radical pairs

Detection of keto-, thioxo- and iminocarbenes and the quintet state triplet-triplet ketocarbene radical pairs

100 Years of the Wolff Rearrangement

Conformational dependence of electronic spectra and zero-field splitting parameters in 2-naphthylphenylcarbene

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