Carbene-alkene complexes between a nucleophilic carbene and electron-poor alkenes.
Spirooxadiazoline 5 is a clean thermal source of tricyclo[6.2.1.0 (2,7)]undec-9-en-11-ylidene (7), a typical foiled carbene. Species 7 can be trapped efficiently at 165 degrees C by electron-deficient alkenes like acrylonitrile and fumaronitrile whereby the anti addition products are obtained exclusively. Higher temperatures, however, favor intramolecular reactions. Density functional theory (DFT) calculations predict the formation of a strong complex between both reactants which actually is a minimum on the free energy scale. These results confirm the nucleophilic character of foiled carbenes and the presence of a significant barrier toward rearrangement.
Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, A-1090 Vienna, Austria.
Jean-Luc
JL
Mieusset
Michael
M
Abraham
Udo H
UH
Brinker