5-Endo Closure of the 2-Formylbenzoyl Radical
The 5-endo cyclization of the 2-formylbenzoyl radical (reaction 2) is shown to be a highly favored process relative to the alternative, 4-exo-trig ring closure. This evidence comes from product studies, including ESR and laser flash photolysis studies of transient radical intermediates, from a nitroxide trapping measurement of the rate constant for cyclization of the 2-formylbenzoyl radical, viz., k2= 2 X 108s-1at 45 °C, and from the estimated favorable enthalpic change for 5-endo cyclization vs 4-exo-trig cyclization. It is suggested that rotation of the formyl group in the initially formed conformer of the 2-formylbenzoyl radical may be the rate limiting step in this cyclization. © 1994, American Chemical Society. All rights reserved.
Journal of the American Chemical Society
5-Endo Closure of the 2-Formylbenzoyl Radical.
Journal of the American Chemical Society,
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