Boron building block assembles tetra-substituted alkenes like Lego

A mild and modular boron-mediated reaction sequence can now assemble diverse chemical building blocks into complex tetra-substituted alkenes – ‘a bit like Lego!’ one of its inventors says. The stereocontrolled process, which the team demonstrated in the synthesis of a panel of drug and natural product compounds, provides access to both E and Z isomers, depending on the chosen conditions. Subsequent computational studies revealed that this tunable selectivity arises from the formation of an unusual borenium intermediate, which the authors believe could have important mechanistic implications for other areas of boron chemistry.