Fast ring opening of unstable mesoionic 1,3-dioxolylium-4-olates to acyloxyketenes: formation of [2+2] cycloadducts of acyloxyketene with several ketenophiles
作者:Masashi Hamaguchi、Naoki Tomida、Eiko Mochizuki、Takumi Oshima
DOI:10.1016/j.tetlet.2003.08.122
日期:2003.10
Fast ring opening of mesoionic 1,3-dioxolylium-4-olate 5, generated by Rh-2(OAc)(4)-catalyzed decomposition of a phenyldiazoacetic anhydride 6, to an acyloxyketene 10 was demonstrated by trapping the ketene 10. Rh-2(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 40 indicates that the acyloxyketene 10 is 9 kcal/mol more stable than the 1,3-dioxolylium-4-olates 5. (C) 2003 Elsevier Ltd. All rights reserved.