Argon-matrix isolation of bis(trifluoromethyl)oxirene, perfluoromethylethyloxirene, and their isomeric ketocarbenes

Torres, M. Rosario; Bourdelande, J. L.; Clement, A.; Strausz, O. P.

doi:10.1021/ja00344a072

Cited by 41 publications

(22 citation statements)

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“…The assignment of an IR band at 2137 cm Ϫ1 to the CϭC bond of 245 is in accordance with highlevel calculations. [208] Matrix isolation of the perfluoroalkyloxirenes 231 (Scheme 33) and 251 was also claimed [216] and disputed. [59b,59c] The addition of oxygen atoms to hexafluorobutyne in cryogenic matrices was recently shown to produce the carbene 177 (Scheme 27, Section 3.4.3.)…”

Section: Computation and 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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Section: Computation and Matrix Isolationmentioning

confidence: 99%

100 Years of the Wolff Rearrangement

2002

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“…The simplest examples of unsaturated heterocycles, oxirene, thiirene and 2-azirene, are highly unstable molecules whose syntheses have only been achieved recently in low temperature argon-matrices [1][2][3], although kinetic evidence for their transient existence had been available since the mid sixties [4,5]. Their instability, apart from the inherent ring strain, has been generally attributed to their antiaromaticity whereby cyclic electron derealization raises the energy.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore the stability of thiirenes, as well as that of oxirenes and 2-azirines, should increase with substituents that have a low migrational aptitude, especially those that are also electron-withdrawing since these will lower the Tr-electron density on the carbon-carbon double bond and consequently release some of the "antiaromatic" character of the molecule. Good examples of these stabilizing effects are the cases of carboethoxymethylthiirene, trifluoromethylthiirene, and bis(trifluoromethyl)thiirene [2] as well as the recent isolation of an intermediate [3] to which the bis (trifluoromethyl)-oxirene structure has been assigned. Thioketenes have been prepared in increasing number since the first reported synthesis of thioketene by Howard in 1962 [15].…”

Section: Introductionmentioning

confidence: 99%

Argon-Matrix Isolation of Bis(carbomethoxy)thiirene: Formation of Acyl and Carbalkoxythioketenes

Torres

Clement

Strausz

1983

Zeitschrift Für Naturforschung B

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Abstract Photolysis of argon-matrix isolated 4,5-bis(carbomethoxy)-1,2,3-thiadiazole with λ = 254 or 265 nm resulted in the almost quantitative formation of bis(carbomethoxy)-thiirene (3g). Photolysis of 3g could only be carried out by long irradiation times at short wavelength λ = 210 nm and resulted mainly in extensive fragmentation instead of the formation of bis(carbomethoxy)thioketene, confirming earlier predictions that substituents, especially electron-withdrawing ones, should stabilize the thiirene ring. Methylcarboethoxy and methylacetylthioketene were obtained, however, in the argon-matrix photolysis or flow thermolysis of 4-methyl-5-carboethoxy-or 4-carboethoxy-5-methyl-1,2,3-thiadiazole and 4-acetyl-5-methyl-1,2,3-thiadiazole, respectively.

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“…Meier mentioned isolation of a methanol-trapping product of an oxirene in his review article.11 •19,20 The Strausz group reported the infrared characterization of both bis(trifluoromethyl)oxirene and (trifluoroacetyl)(trifluoromethyl)carbene under matrix-isolation conditions in 1983. 23 However, Lemal and co-workers demonstrated that the species originally assigned as the -ketocarbene is actually the a-ketodiazirine isomer of the -diazo ketone starting material. 24 In addition, they failed to generate the oxirene under irradiation conditions, which were similar but not identical with those of Strausz.…”

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Mechanistic studies on the Wolff rearrangement: the chemistry and spectroscopy of some .alpha.-keto carbenes

McMahon¹,

Chapman²,

Hayes³

et al. 1985

J. Am. Chem. Soc.

103

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Photochemical extrusion of dinitrogen from diazo ketones 1-4 matrix isolated in argon at 10-15 K produces a-ketocarbenes 5, 6, and 8. UV-vis, infrared, and electron spin resonance spectroscopy identify the -ketocarbenes, which are further characterized by trapping with carbon monoxide and dioxygen. Excitation (T0-Tt) of the -ketocarhenes leads to rapid ring contraction of 5-*9 and slow ring contraction of 6-*10 and 8-*12. This trend parallels the increasing degree of strain in the product ketenes. Shorter wavelength irradiation causes rapid ring contraction of 6-*10 and 8-1-12. The stepwise

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Argon-matrix isolation of bis(trifluoromethyl)oxirene, perfluoromethylethyloxirene, and their isomeric ketocarbenes

Cited by 41 publications

References 0 publications

100 Years of the Wolff Rearrangement

100 Years of the Wolff Rearrangement

Argon-Matrix Isolation of Bis(carbomethoxy)thiirene: Formation of Acyl and Carbalkoxythioketenes

Mechanistic studies on the Wolff rearrangement: the chemistry and spectroscopy of some .alpha.-keto carbenes

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