Fast ring opening of unstable mesoionic 1,3-dioxolylium-4-olates to acyloxyketenes: formation of [2+2] cycloadducts of acyloxyketene with several ketenophiles |
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Authors: | Masashi Hamaguchi Naoki TomidaEiko Mochizuki Takumi Oshima |
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Affiliation: | Department of Materials Chemistry, Graduate School of Engineering, Osaka University, Toyonaka 560-0043, Japan |
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Abstract: | Fast ring opening of mesoionic 1,3-dioxolylium-4-olate 5, generated by Rh2(OAc)4-catalyzed decomposition of a phenyldiazoacetic anhydride 6, to an acyloxyketene 10 was demonstrated by trapping the ketene 10. Rh2(OAc)4-catalyzed decomposition of p-nitrophenyldiazoacetic p-chlorobenzoic anhydride 6a in the presence of ketenophiles such as dihydrofuran, carbodiimides, and imines did not give 1,3-dipolar cycloadducts with the 1,3-dioxolylium-4-olates 5a, but their [2+2]-cycloadducts with the acyloxyketene 10a. PM3 calculation of heats of formation of a 1,3-dioxolylium-4-olate 5 and an acyloxyketene 10 indicates that the acyloxyketene 10 is 9 kcal/mol more stable than the 1,3-dioxolylium-4-olates 5. |
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Keywords: | mesoionic compounds 1,3-dioxolylium-4-olates ring opening ketenes [2+2]-cycloaddition |
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