Showing papers by "Curt Wentrup published in 2001"
TL;DR: Flash vacuum thermolysis of a large variety of heterocyclic compounds is a useful means of production of ketenes, ketenimines, thioketenes, allenes, iminopropadienones, bis(imino)propadienes, imINopropaddienethiones, carbodiimides, isothiocyanates, acetylenes, fulminic acid, Nitrile imines and nitrile ylides, nitriles, cyanamides, cyanates, and other compounds, often
37 citations
TL;DR: In his Perspective, [Wentrup] charts recent progress in the synthesis of stable carbenes and highlights the report by [ SolA© et al .], who have succeeded in synthesizing an unusually stable carbene that retains its reactivity.
Abstract: Carbenes are molecules with a carbon atom bound to just two other atoms. These species are usually transient intermediates. In his Perspective, [Wentrup][1] charts recent progress in the synthesis of stable carbenes. He highlights the report by [ SolA© et al .][2], who have succeeded in synthesizing an unusually stable carbene that retains its reactivity. Such species may find future application as catalysts.
[1]: http://www.sciencemag.org/cgi/content/full/292/5523/1846
[2]: http://www.sciencemag.org/cgi/content/short/292/5523/1901
21 citations
TL;DR: In this article, the alpha-oxoketene-pyridine zwitterion 4 was obtained from dipivaloylketene and its dimers with DMAP in acetonitrile.
18 citations
TL;DR: In this paper, it was shown that mesoionic pyrido[1,2-a]pyrimidinium olates undergo rearrangement to the lower-energy pyridopyrimidine 7 in solution at ordinary temperatures.
Abstract: Mesoionic pyrido[1,2-a]pyrimidinium olates 9 undergo rearrangement to the lower-energy pyridopyrimidinones 7 in solution at ordinary temperatures (t1/2 ≈ 51 min at 75 °C), formally via the higher-energy ketene valence isomers 11 These ketenes are not directly detectable, and DFT calculations at the B3LYP/6-31G* level indicate that the rearrangement may be concerted via the ketenoid transition state 11TS, although the ketene conformer 11M is locally stable FVT of the pyridopyrimidinones 7 is a method of synthesis of (2-pyridyl)iminopropadienone 4, a reaction thought to proceed via ring opening to the same ketenes 11 followed by elimination of the 2-(methylamino)pyridine 8 Recombination of 8 and 4 leads to mesoions 9 together with minor amounts of the isomers 10
15 citations
TL;DR: Aryliminopropadienethiones 9 have been generated by flash vacuum thermolysis of isoxazolones of the type 5 and characterized by mass spectrometry and matrix isolation IR spectroscopy in conjunction with DFT calculations and chemical trapping.
Abstract: Aryliminopropadienethiones 9 have been generated by flash vacuum thermolysis of isoxazolones of the type 5 and characterized by mass spectrometry and matrix isolation IR spectroscopy in conjunction with DFT calculations and chemical trapping.
13 citations
Journal Article•
TL;DR: In this paper, a short review describes the preparation and chemistry of sterically stabilized α-oxoketenes, which can be isolated and handled as true neat compounds, and their reactions with dienophiles afford [4+2] -as well as [2+2]- cycloadducts depending on their ability to adopt that conformation suitable for each type of cycloaddition reactions.
Abstract: This short review describes the preparation and chemistry of sterically stabilized α-oxoketenes, which can be isolated and handled as true neat compounds. Their reactions with dienophiles afford [4+2] - as well as [2+2] cycloadducts depending on their ability to adopt that conformation suitable for each type of cycloaddition reactions. Addition of nucleophiles leads either to dipivaloylacetic acid derivatives as expected products or to the rare molecular skeleton of mono-or bifunctionalized bridged bisdioxines, which exhibit axial chirality. The bifunctionalized derivatives may serve as novel spacer units in several macrocyclic systems.
6 citations
TL;DR: The most stable C2S4.+ structure corresponds to a CS2 dimer with a C-2 symmetry, 52 kJ mol(-1) more stable than the lowest energy covalently bound structure consisting of a four-membered ring thioketene species as mentioned in this paper.
5 citations
TL;DR: In this article, the EPR spectrum of 4-azidotetrachloropyridine (4-pyridylnitrene) is characterized by zero-field splitting parameters.
Abstract: Photolysis of 4-azidotetrachloropyridine isolated in inert matrices at low temperatures leads to formation of triplet tetrachloro-4-pyridylnitrene as the sole product of the photochemical reaction. In the EPR spectrum, this nitrene gives an intense signal and is characterized by zero-field splitting parameters. The UV spectrum of nitrene in solid argon contains a series of high-intensity and medium-intensity absorption bands. The IR spectrum in solid argon agrees well with nonempirical and semiempirical calculations. On exposure to light, nitrene easily reacts with molecular carbon(II) oxide, forming the corresponding isocyanate. Irradiation with light does not result in formation of bicyclic azirine, but initiates the reverse reaction of fixation by nitrene of the molecular nitrogen contained in the solid argon, leading to the starting azide.
3 citations
TL;DR: In this article, a review of the gas phase chemistry of 1,2-and 1,3-dipolar systems with carbon-nitrogen bond is presented, together with their methods of preparation and the experiment used to identify them.
Abstract: This review will be concerned with the gas phase chemistry of 1,2- and 1,3-dipolar systems that contain a carbon–nitrogen bond. Although most of these compounds are stable molecules under normal conditions, certain congeners are reactive species that cannot be prepared using conventional procedures. The isolation and observation of these elusive compounds therefore require appropriate experimental conditions such as those provided by the gas phase of a mass spectrometer. In these experiments, the radical cations, corresponding to the molecule under study, must be prepared via indirect procedures, including dissociative electron ionization, on-line flash-vacuum pyrolysis-mass spectrometry, or ion-molecule reactions. Their characterization is mainly based on collisional activation and ion-molecule reactions. The formation of the corresponding highly reactive neutrals is attempted by neutralization-reionization mass spectrometry. This review presents more than one hundred different molecules together with their methods of preparation and the experiment used to identify them. © 2000 John Wiley & Sons, Inc., Mass Spec Rev 19: 367–389, 2000
2 citations
1 citations
TL;DR: In this paper, the open-chain dipivaloylacetic acid derivatives 3, 5, 6, 9 and 10 were obtained with methylhydrazine as well as 2,6-dimethylaniline.
Abstract: Dipivaloylketene 1 and its dimer 2 add several NH2-nucleophiles affording the open-chain dipivaloylacetic acid derivatives 3, 5, 6, 9 and 10. With methylhydrazine as well as 2,6- dimethylaniline the 2:1 products 8 and 11, respectively, are formed. The tetracarbonyl compounds 3a-c only undergo PPA-induced cyclocondensation, and with concomitant loss of one pivaloyl group the pyrimidine-2,4-diones 4a-c are obtained.