Oxidative heterocoupling between two Grignardreagents RMgX and R′MgX is made possible by manganese catalysis with O2 as an oxidant. This procedure, development of which was based on mechanistic analysis of the corresponding homocoupling reaction, can be steered towards the heterocoupling product at the expense of the homocoupling products by judicious choice of the R and R′ groups (see examples).
Atmospheric oxygen was used for the first time as an oxidant in metal-catalyzed homocoupling of Grignard reagents. These manganese- or iron-catalyzed reactions are efficient, cheap, and eco-friendly. They are applicable to the large-scale synthesis of symmetrical conjugated compounds.