1,2‐Bis(trifluoromethyl)ethene‐1,2‐dicarbonitrile and Vinyl Ethers: Cyclic Ketene Imines on the Pathway to 1 : 2 Cycloadducts |
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Authors: | Gonzalo Urrutia Desmaison Rolf Huisgen Heinrich Nöth |
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Institution: | 1. Institut für Chemie und Biochemie der Freien Universit?t Berlin, Takustrasse 3, D‐14195 Berlin;2. Department Chemie der Ludwig‐Maximilians‐Universit?t München, Butenandt‐Strasse 5?–?13, D‐81377 München |
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Abstract: | (E)‐ and (Z)‐1,2‐bis(trifluoromethyl)ethene‐1,2‐dicarbonitrile (BTE; (=E)‐ and (Z)‐1,2‐bis(trifluoromethyl)but‐2‐enedinitrile) were reacted with an excess of methyl vinyl ether, used as solvent, and furnished 1 : 2 adducts 6 (54%) and cyclobutanes 3 as 1 : 1 adducts (41%). The four diastereoisomeric bis‐adducts 6 (different ratios from (E)‐ and (Z)‐BTE) are derivatives of 1‐azabicyclo4.2.0]oct‐5‐ene; X‐ray analyses and 19F‐NMR spectra revealed their structures. Since the cyclobutanes 3 are resistant to vinyl ether, the pathways leading to mono‐ and bis‐adducts must compete on the level of the intermediate l,4‐zwitterions 1 and 2 . The latter either cyclize to the cyclobutanes 3 or to six‐membered cyclic ketene imines 8 which accept a second molecule of vinyl ether to yield the bis‐adducts 6 . The occurrence of the highly strained ketene imines 8 gains credibility by comparison to stable seven‐membered cyclic ketene imines recently reported. |
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Keywords: | Ketene imines Ethene‐1 2‐dicarbonitrile 1 2‐bis(trifluoromethyl)‐ Cycloadditions X‐Ray crystallography |
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