A Mild Pummerer-Like Reaction of Carbohydrate-Based Selenoethers and Thioethers Involving Linear Ozonide Acetates as Putative Intermediates

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• 作者：Natacha Veerapen ; Stephanie. A. Taylor ; Charles. J. Walsby ; and B. Mario Pinto
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：January 11, 2006
• 年：2006
• 卷：128
• 期：1
• 页码：227 - 239
• 全文大小：257K
• 年卷期：v.128,no.1(January 11, 2006)
• ISSN：1520-5126

文摘

Pummerer-like rearrangements of carbohydrate-based heterocycles containing selenium andsulfur were investigated. To the best of our knowledge, this is the first report on the Pummerer rearrangementin selenoheterocycles. Ozonization of 1,4-anhydro-D-galactitol or 1,5-anhydroxylitol derivatives containingsulfur or selenium as the ring heteroatom gave unstable intermediates that were attributed to ozonides.These intermediates decomposed upon warming to give selenoxides or sulfoxides. Significantly, additionof acetic anhydride at low temperature to the ozonization reaction mixtures gave Pummerer-rearrangementproducts after warming to ambient temperature. However, when the isolated selenoxides or sulfoxideswere treated with acetic anhydride, Pummerer rearrangement occurred but the sulfoxides required muchhigher reaction temperatures. The latter results are at variance with the former and are interpreted in termsof the rearrangement of the ozonide acetate intermediates in the former cases. To probe whether therearrangement proceeded heterolytically via extrusion of singlet oxygen or homolytically via the generationof radical species, trapping experiments with rubrene and electron paramagnetic resonance (EPR) studieswith the radical trap DMPO were performed. The results of these experiments are consistent with theintermediacy of radical species and suggest a new and milder synthetic method to generate Pummerer-type products.