Triplet diphenylcarbenes protected by o-Aryl groups

Journal of the American Chemical Society
Kyoko MonguchiHideo Tomioka

Abstract

Diphenyldiazomethanes (2a-N(2)) having phenyl groups at the ortho positions were prepared and the corresponding diphenylcarbenes (2a) photolytically generated from them were characterized not only by the traditional product analysis method but also by ESR and UV/vis spectroscopy in a rigid organic matrix at low temperature and in laser flash photolysis in solution at room temperature. Product analysis indicated that fluorenes 4a are formed almost exclusively. Fluorene is most likely produced by the attack of singlet carbene (1)2a on an ortho carbon of the phenyl substituent to generate isofluorene, followed by 1,5-H shift. Irradiation of 2a-N(2) in a 2-methyltetrahydrofuran (2-MTHF) matrix at 77 K gave ESR signals ascribable to triplet carbenes ((3)2a). UV/vis spectra of (3)2a were obtained by irradiating 2a-N(2) under identical conditions. However, laser flash photolysis (LFP) of 2a-N(2) in degassed benzene at room temperature showed transient absorption bands completely different from those observed in photolysis in the 2-MTHF matrix at 77 K. The transient band decayed in first-order with a rate constant of 7.6 x 10(4) s(-1), which was not retarded by deuterium substitution of o-phenyl hydrogens. Essentially the same transien...Continue Reading

References

Sep 15, 1988·Physical Review A: General Physics·A D Becke
Aug 9, 2001·Nature·H D Roth
Jan 17, 2002·Journal of the American Chemical Society·Hideo TomiokaKatsuyuki Hirai
Aug 17, 2002·The Journal of Organic Chemistry·B Andes Hess, John E Baldwin
Nov 15, 2002·Journal of the American Chemical Society·Frederick D LewisMichael Rubin
May 23, 2003·Angewandte Chemie·Wolfgang Kirmse
Aug 2, 2003·Journal of the American Chemical Society·Igor V AlabuginFrederick D Lewis
Jan 30, 2004·Journal of the American Chemical Society·Tetsuji ItohHideo Tomioka
Sep 1, 1986·Journal of the American Chemical Society·W KirmseK N Houk

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Citations

Aug 15, 2013·The Journal of Organic Chemistry·Michèle J Régimbald-Krnel, Curt Wentrup
May 28, 2015·The Journal of Physical Chemistry. a·Curt WentrupDavid Kvaskoff
Jun 23, 2016·Chemical Record : an Official Publication of the Chemical Society of Japan ... [et Al.]·Masayuki Iwasaki, Yasushi Nishihara
May 20, 2009·Chemical Reviews·Katsuyuki HiraiHideo Tomioka

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