The first synthesis of cyclopropanone acetals from the reaction of Fischer carbene complexes with ketene acetals |
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| Institution: | 1. School of Chemical Engineering, Hefei University of Technology (HFUT), Tunxi Road 193, 230009, Hefei, PR China;2. School of Materials Science and Engineering, HFUT, Tunxi Road 193, 230009, Hefei, PR China;1. School of Computer and Information Technology, Shanxi University, Taiyuan, Shanxi 030006, China;2. Department of Radiation Oncology, Rush University Medical Center, Chicago, IL 60612, USA;3. Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL 60637, USA;1. Department of Chemical Engineering, Inner Mongolia University of Technology, 010051 Huhhot, China;2. School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, 430074 Wuhan, China;1. Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an, Shaanxi 710054, PR China;2. College of Chemistry and Chemical Engineering, Yan’an University, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan’an, Shaanxi 716000, PR China;3. Department of Applied Chemistry, School of Science & State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, PR China;4. School of Chemistry and Environment, Jia Ying University, Meizhou, Guangdong 514015, PR China |
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| Abstract: | The reaction of iso-propoxy stabilized Fischer carbene complexes with ketene acetals gives moderate to excellent yields of cyclopropanone acetals when carried out under a carbon monoxide atmosphere. This is in contrast to the known reaction of methoxy substituted complexes which give cyclic ortho esters under the same conditions. A mechanism is proposed which involves a branch point between the two products as the zwitterionic intermediate resulting from nucleophilic addition of the ketene acetal to the carbene carbon. A 1,3-migration of the methoxyl group to the cationic center leads to the ortho ester and a ring closure by backside attack leads to the cyclopropanone acetal. A double-labeling experiment shows that the 1,3-migration occurs by an intramolecular process that is proposed to involve a bridging oxonium ion. The effect of the isopropoxy group is thus interpreted to be to sterically hinder the formation of a bridged oxonium ion. |
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