Cuᴵᴵ-katalysierte Kupplung von Cyclopropyl-carbenoiden


  • Markus Borer
  • Thomas Loosli
  • Markus Neuenschwander Institut für organische Chemie, Universität Bern, Freiestrasse 3, CH-3012 Bern



Contrary to the reaction of 'Hückel anions' like cyclopentadienide or cyclononatetraenide, treatment of 1-bromo-1-lithio-carbenoids 2 with 1 mol-equiv. of CuCl2 in THF does not result in an oxidative coupling 28 (see Scheme 2), but in a formal dimerization of two carbenes to give bi(cyclopropylidenes) 10. Reaction parameters influencing the yields are discussed in the case 2a10a (R=PhS). Yields of ca. 40% of 10a are obtained under 'kinetic control' at high concentrations of 2a and in THF/Et2O mixtures. Besides CuCl2, which is catalytically active, FeCl3 has been found to be a coupling agent as well, while AgBF4, AgCl, CoF3, and CuCl were inactive in THF. Mixed couplings of two different carbenoids are possible, while diastereoselectivity of the active transition metal complex seems to be low. First experimental results obtained with 2b (R=BuO) and 2c (R=PhCH2) hint at a considerable scope of the sequence 210.




How to Cite

M. Borer, T. Loosli, M. Neuenschwander, Chimia 1991, 45, 382, DOI: 10.2533/chimia.1991.382.