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Chiang Y, Gaplovsky M, Kresge AJ, et al. Photoreactions of 3-diazo-3H-benzofuran-2-one; dimerization and hydrolysis of its primary photoproduct, a quinonoid cumulenone: a study by time-resolved optical and infrared spectroscopy. J Am Chem Soc. 2003;125(42):12872-80doi: 10.1021/ja0365476.
Chiang, Y., Gaplovsky, M., Kresge, A. J., Leung, K. H., Ley, C., Mac, M., Persy, G., Phillips, D. L., Popik, V. V., Rödig, C., Wirz, J., & Zhu, Y. (2003). Photoreactions of 3-diazo-3H-benzofuran-2-one; dimerization and hydrolysis of its primary photoproduct, a quinonoid cumulenone: a study by time-resolved optical and infrared spectroscopy. Journal of the American Chemical Society, 125(42), 12872-80. https://doi.org/10.1021/ja0365476
Chiang, Yvonne, et al. "Photoreactions of 3-diazo-3H-benzofuran-2-one; dimerization and hydrolysis of its primary photoproduct, a quinonoid cumulenone: a study by time-resolved optical and infrared spectroscopy." Journal of the American Chemical Society vol. 125,42 (2003): 12872-80. doi: https://doi.org/10.1021/ja0365476
Chiang Y, Gaplovsky M, Kresge AJ, Leung KH, Ley C, Mac M, Persy G, Phillips DL, Popik VV, Rödig C, Wirz J, Zhu Y. Photoreactions of 3-diazo-3H-benzofuran-2-one; dimerization and hydrolysis of its primary photoproduct, a quinonoid cumulenone: a study by time-resolved optical and infrared spectroscopy. J Am Chem Soc. 2003 Oct 22;125(42):12872-80. doi: 10.1021/ja0365476. PMID: 14558836.
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J Am Chem Soc. 2003 Oct 22;125(42):12872-80. doi: 10.1021/ja0365476.

Photoreactions of 3-diazo-3H-benzofuran-2-one; dimerization and hydrolysis of its primary photoproduct, a quinonoid cumulenone: a study by time-resolved optical and infrared spectroscopy.

Journal of the American Chemical Society

Yvonne Chiang, Martin Gaplovsky, A Jerry Kresge, King Hung Leung, Christian Ley, Marek Mac, Gabriele Persy, David L Phillips, Vladimir V Popik, Christoph Rödig, Jakob Wirz, Yu Zhu

Affiliations

  1. The Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada. [email protected]

PMID: 14558836 DOI: 10.1021/ja0365476

Abstract

Light-induced deazotization of 3-diazo-3H-benzofuran-2-one (1) in solution is accompanied by facile (CO)-O bond cleavage yielding 6-(oxoethenylidene)-2,4-cyclohexadien-1-one (3), which appears with a rise time of 28 ps. The expected Wolff-rearrangement product, 7-oxabicyclo[4.2.0]octa-1,3,5-trien-8-ylidenemethanone (4), is not formed. The efficient light-induced formation of the quinonoid cumulenone 3 opens the way to determine the reactivity of a cumulenone in solution. The reaction kinetics of 3 were monitored by nanosecond flash photolysis with optical (lambda(max) approximately 460 nm) as well as Raman (1526 cm(-1)) and IR detection (2050 cm(-)(1)). Remarkably, the reactivity of 3 is that expected from its valence isomer, the cyclic carbene 3H-benzofuran-2-one-3-ylidene, 2. In aqueous solution, acid-catalyzed addition of water forms the lactone 3-hydroxy-3H-benzofuran-2-one (5). The reaction is initiated by protonation of the cumulenone on its beta-carbon atom. In hexane, cumulenone 3 dimerizes to isoxindigo ((E)-[3,3']bibenzofuranylidene-2,2'-dione, 7), coumestan (6H-benzofuro[3,2-c][1]benzopyran-6-one, 8), and a small amount of dibenzonaphthyrone ([1]benzopyrano[4,3-][1]benzopyran-5,11-dione, 9) at a nearly diffusion-controlled rate. Ab initio calculations (G3) are consistent with the observed data. Carbene 2 is predicted to have a singlet ground state, which undergoes very facile, strongly exothermic (irreversible) ring opening to the cumulenone 3. The calculated barrier to formation of 4 (Wolff-rearrangement) is prohibitive. DFT calculations indicate that protonation of 3 on the beta-carbon is accompanied by cyclization to the protonated carbene 2H(+), and that dimerization of 3 to 7 and 9 takes place in a single step with negligible activation energy.

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