Neue Bi(cyclopropylidene) durch CuCl 2 ‐katalysierte ‘Carben‐Dimerisieiung’ von 1‐Bromo‐1‐lithiocyclopropanen

New Bi(cyclopropylidenes) by CuCl 2 ‐Induced ‘Carbene Dimerization’ of 1‐Bromo‐1‐lithiocycIopropanes A series of so far unknown bi(cyclopropylidenes) 5 are prepared in a simple one‐pot reaction by halogenolithio exchange between 1,1‐dibromocyclopropanes 1a – c as well as 1e – i and BuLi at −95°, to give 1‐bromo‐1‐lithiocyclopropanes 2a – c as well as 2e – i , followed by treatment with CuCl 2 at low temperature and a simple workup at room temperature ( Table 1 ). The influence of reaction parameters on yields of 5 ( Tables 2, 4 , and 5 ) and diastereoselectivity of the reaction 2 → 5 ( Table 3 ) are discussed. In view of an elucidation of the reaction mechanism, first kinetic experiments of the quantitative reaction 1c → 2c → 5c are reported.