Cross-coupling reactions have been developed between C2-substituted 1-bromocyclobut-1-enes and Grignard reagents using two effective catalysts, e.g., Fe(acac)3 and Ni(acac)2. The iron catalyst works in THF but requires NMP as the co-solvent, with the advantage of achieving cross-coupling reactions with alkyl Grignard reagents. The nickel catalyst was able to promote the reactions in THF without any additive and showed high reactivity with electron-rich aryl Grignard reagents. These catalysts gave various types of substituted cyclobutenes in good yields.
Key words
cross-coupling - catalysis - iron - nickel - cyclobutenes - Grignard reagents
