Gas‐Phase Kinetics of Pyrolysis of 3,3‐Dimethylcyclopropene and Its 1‐Trimethylsilyl Derivative The Effect of Silyl Substitution on Cyclopropene Isomerisation
作者： Robin Walsh , Sven Untiedt , Michael Stohlmeier , Armin de Meijere
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摘要: The gas-phase pyrolysis of 3,3-dimethylcyclopropene (1) in the temperature range 185–225°C gives 3-methyl-1-butyne (2) (91%) and isoprene (3) (9%). 3,3-dimethyl-1-trimethylsilylcyclopropene (4) 195–235°C 3-methyl-1-trimethylsilyl-1-butyne (5) (99%) trans-3-methyl-1-trimethylsilyl-1,3-butadiene (6) (1%). Both rearrangements are homogeneous, first-order, unimolecular reactions with following pressure-independent Arrhenius parameters. Rather surprisingly, trimethylsilyl group deactivates cyclopropene respect to its isomerisation. Possible mechanisms discussed. Gas-Phasen-Kinetik der Pyrolyse von 3,3-Dimethylcyclopropen und seinem 1-Trimethylsilyl-Derivat. – Der Effekt Silyl-Substitution auf die Cyclopropen-Isomerisierung Die Gasphasen-Pyrolyse im Temperaturbereich ergibt 3-Methyl-1-butin Isopren Die 3,3-Dimethyl-1-trimethylsilylcyclopropen fuhrt zu 3-Methyl-1-trimethylsilyl-1-butin trans-3-Methyl-1-trimethylsilyl-1,3-butadien Beide Umlagerungen sind homogene, unimolekulare Reaktionen erster Ordnung mit den folgenden druck-unabhangigen Arrhenius-Parametern. Uberraschenderweise desaktiviert Trimethylsilyl-Gruppe das Cyclopropen bezug seine Isomerisierung. Mogliche Mechanismen werden diskutiert.
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