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  • 1
    ISSN: 0947-3440
    Keywords: Matrix isolation ; Carbenes ; Rearrangements ; Furfurylidene ; Ketenes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Warming the dilithium salt 7 of furan-2,5-dicarboxaldehyde bis(tosylhydrazone) to 110°C and subsequently trapping the products in solid argon at 10 K resulted in the formation of 1-diazo-hex-3-en-5-yn-2-one (9). The intermediate 2,5-bis(diazomethylfuran) (6) is too labile to be directly observed under these conditions. The formation of 9 from 6 is rationalized by the loss of one nitrogen molecule and rapid rearrangement of the intermediate carbene 8. Photolysis of 9 leads to loss of the second nitrogen molecule and rearrangement of the resulting carbene 12. The major path is the Wolff rearrangement to hexa-1,3-dien-5-yn-1-one (11); the minor path is the intramolecular cycloaddition of the carbene center to the triple bond to 1H-bicyclo[3.1.0]hexa-3,5-dien-2-one (2). UV photolysis of 2 results in the ring opening to yield again ketene 11. The mechanism of this rearrangement was investigated by deuterium labeling.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-193X
    Keywords: Cyclopropanone ; Allene oxide ; Matrix isolation ; Photochemistry ; Flash vacuum thermolysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The flash vacuum pyrolysis of 3,3,5,5-tetramethylpyrazolin-4-one (4) with subsequent trapping of the products in argon at 10 K results in the formation of a complex product mixture with tetramethylcyclopropanone (5) as one of the minor constituents. The 193 nm photochemistry of matrix-isolated 4 is much cleaner, yielding cyclopropanone 5 and allene oxide 9 as the major products. The reaction of tetramethylallene 13 with oxygen atoms yields the same product mixture of 5 and 9 and thus provides an independent route to these species. The experimental IR spectra of 5 and 9 are in good agreement with the results from DFT calculations.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99377_s.pdf or from the author.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0009-2940
    Keywords: Quinone diazides ; Matrix isolation ; Electronic structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of p-benzoquinone diazides were investigated by 13C-NMR and IR spectroscopy as well as by semiempirical and abinitio calculations. In addition, X-ray structure analyses of the parent compound and three derivatives were performed. The electronic structure and effects of substituents can be described in terms of diazoketo and diazonium phenolate resonance structures. While alkyl groups as substituents have only a minor influence on quinone diazides, electron-withdrawing substituents lead to a larger participation of the aromatic diazonium phenolate structure. Benzoannellation, on the other hand, leads to a decrease of the interaction between the keto and diazo functional group and to properties more reminiscent of “ordinary” ketones and diazo compounds.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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