Photoactivated α‐ketocarbenes: Formation and isomerization reactions. RRKM calculations with semi‐empirical parameters (AM1, MNDOC)

Bachmann, Christian; N'Guessan, Thomas Yao

doi:10.1002/kin.550260606

Cited by 5 publications

(2 citation statements)

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“…H, and Me, respectively, in ethylmethylcarbene. [81] Semiempirical (AM1) methods were employed to compare 24 with 38, [82] and to analyze substituent effects on the rearrangement of 25. [83] A comprehensive theoretical investigation of migratory aptitudes has yet to appear.…”

Section: Migratory Aptitudesmentioning

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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Section: Migratory Aptitudesmentioning

confidence: 99%

100 Years of the Wolff Rearrangement

2002

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“…In our case the singlet±triplet gap is predicted to be about 2 kcal/mol at UB3LYP/6-31G** level, and so both species can exist in rapid equilibrium [13]. Nevertheless, it has been reported that the shifts on the triplet ground-state PES have larger energy barriers than that on the ®rst singlet-state PES [30,32]. Therefore, in this paper we shall deal with the shifts on the ®rst excited singlet-state PES, i.e.…”

Section: Regular Articlementioning

confidence: 76%

The influence of protecting the hydroxyl group of β-oxy-α-diazo carbonyl compounds in the competition between Wolff rearrangement and [1,2]-hydrogen shift. Density functional theory study and topological analysis of the charge density

Calvo-Losada

Sordo

Lopez‐Herrera

et al. 2000

Theoretical Chemistry Accounts: Theory, Computation, and Modeli

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The in¯uence of protecting the hydroxyl group of a b-oxy-a-diazo carbonyl compound on the competition between the Wol rearrangement (WR) and the [1,2]-hydrogen shift (HS) was investigated theoretically. Stationary points on the potential-energy surface were located with the B3LYP density functional and the 6-31G** basis set. For the basic system geometry optimisations at B3LYP/6-311+G** were performed to validate the reliability of the B3LYP/6-31G** calculations. Singlepoint energy calculations were carried out at the B3LYP/ 6-311+G** level on the B3LYP/6-31G**-optimised geometries. Further insight into the processes was achieved with the aid of the theory of``atoms in molecules'' of Bader. The calculated energy barriers qualitatively predicted the yields of HS and WR obtained experimentally. In order to rationalise the calculated energy barriers, it was necessary to take into account not only the electronegativity of the protective groups but also the alignment of the migrating groups with the depletion sites at the carbene centre. Further, when the hydroxyl group was not protected the existence of an intramolecular hydrogen bond played an important role in both HS and WR.

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