Direct measurements of the rates of 1,3- and 1,5-sigmatropic hydrogen shifts in the photo-Fries rearrangements of phenyl acetate
1994; Elsevier BV; Volume: 223; Issue: 5-6 Linguagem: Inglês
10.1016/0009-2614(94)80006-5
ISSN1873-4448
AutoresTadashi Arai, Seiji Tobita, Haruo Shizuka,
Tópico(s)Photochemistry and Electron Transfer Studies
ResumoThe rate constants for the 1,3- and 1,5-sigmatropic hydrogen shifts of the photo-Fries rearranged intermediates of phenyl acetate produced by laser flash photolysis at 266 nm were directly measured in several solvents. The rate constant for the 1,3-hydrogen shift (3.6 s−1) was faster than that for the 1,5-shift (6.5×10−2 s−1) in the ground state in methylcyclohexane at 293 K, contrary to the expectation by the Woodward—Hoffmann rule. In protic solvents, ethanol and methanol, a remarkable increase in the rate constants (∼105 s−1) was observed. A tentative mechanism including the role of the non-bonding electrons of the intermediates is discussed.
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