Iron–copper cooperative catalysis is shown to be effective for an alkene–Grignard exchange reaction and alkylmagnesiation of alkynes. The Grignard exchange between terminal alkenes (RCH CH2) and cyclopentylmagnesium bromide was catalyzed by FeCl3 (2.5 mol%) and CuBr (5 mol%) in combination with PBu3 (10 mol%) to give RCH2CH2MgBr in high yields. 1-Alkyl Grignard reagents add to alkynes in the presence of a catalyst system ...