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Ernst Schaumann

Other affiliations: University of Hamburg
Bio: Ernst Schaumann is an academic researcher from Clausthal University of Technology. The author has contributed to research in topics: Cycloaddition & Thioketene. The author has an hindex of 26, co-authored 349 publications receiving 2944 citations. Previous affiliations of Ernst Schaumann include University of Hamburg.


Papers
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84 citations

Journal ArticleDOI
TL;DR: In this article, at room temperature α-elimination occurs in the carbenoids 2b-d with formation of the alkyliden carbenes 15b−d, which react further to yield the butatrienes 13b−D, the alkenes 14b-D, and in the case of 15d to give the CH-insertion product 16.
Abstract: Bei −78°C reagieren die Dialkylthioketene 1a–d mit Phenyl- und Methyllithium unter thiophiler Addition zu den Thioathern 3a–d und 4. Die carbenoide Zwischenstufe konnte fur 2c mit Kohlendioxid und mit Methyljodid zu 7 und 8 abgefangen werden. Bei Raumtemperatur gehen die Carbenoide 2b–d α-Eliminierung zu den Alkylidencarbenen 15b–d ein, die zu den Butatrienen 13b–d, den Alkenen 14b–d und fur 15d zum CH-Insertionsprodukt 16 weiterreagieren. Thiophilic Addition of Phenyllithium to Thioketenes At −78°C the dialkylthioketenes 1a–d react with phenyl-and methyllithium in thiophilic additions to give the thioethers 3a–d and 4. The carbenoid intermediate 2c could be trapped with carbon dioxide or methyl iodide to 7 and 8. At room temperature α-elimination occurs in the carbenoids 2b–d with formation of the alkylidencarbenes 15b–d, which react further to yield the butatrienes 13b–d, the alkenes 14b–d, and in the case of 15d to give the CH-insertion product 16.

74 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that four-membered rings can be cleaved thermally, Photochemically, or catalytically into two π-bonded fragments.
Abstract: Four-membered rings can be cleaved thermally, Photochemically, or catalytically into two π bonded fragments. Theoretical calculations, kinetic studies, and investigations of stereo- and regioselectivity have been undertaken to clarify the question of whether the reaction involves one or two steps and to permit predictions on its course. [2 + 2]-Cycloreversions have been used to clarify the structure of four-membered rings, to prepare highly reactive π electron-systems and–in combination with a [2 + 2]-cycloaddition–to protect double bonds. The combination of a cycloaddition and-reversion can be used to convert a carbonyl group into an olefin. Starting with compounds containing annelated four-membered rings, compounds with two functional groups or large ring systems can be prepared. [2 + 2]-Cycloreversions have also been discussed in connection with storage of solar energy.

61 citations

Book ChapterDOI
01 Jan 2007
TL;DR: A survey of the structure and synthetic applications of organosulfur compounds is given in this article, where the emphasis is on the key features of organo-sulfur chemistry.
Abstract: A survey of the structure and synthetic applications of organosulfur compounds is given. The emphasis is on the key features of organosulfur chemistry.

52 citations


Cited by
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TL;DR: One of the goals of this Review is to attract the attention of the scientific community as to the benefits of using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.
Abstract: The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C–C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of...

1,228 citations

01 Jan 1958
TL;DR: In this article, it was shown that the effects of zero point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0.
Abstract: Kraitchman has shown that a single isotopic substitution on an atom is sufficient to determine directly the coordinates of that atom with respect to the principal axes of the original molecule. Kraitchman's formulas represent exact solutions of the equations for the equilibrium moments of inertia. However, the effects of the zero‐point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0. These coordinates have here been called r (substitution) or rs, and it is found that rs≃(r0+re)/2, and Is= ∑ imirsi2≃(I0+Ie)/2.In the usual method of solution, the coordinate of one atom is determined from the equation for I0, and therefore the difference I0—Is must be made up by this one coordinate. This introduces a large error in the structures normally determined from ground state constants, and results in variations of 0.01 A in structures determined from different sets of isotopic species. If instead, we obtain the structure on...

839 citations