Powerful acid prevails upon reluctant alkenes to react

To drive reactions forward, catalytic Brønsted acids wield protons to provoke molecular bonds into action. These organic catalysts have acted on obliging, heteroatom-containing bonds in a variety of transformations, but they’ve been unable to tempt simple, unactivated alkenes—a class of substrates that has been dominated by efficient transition-metal catalysis. Researchers led by Benjamin List at the Max Planck Institute for Kohlenforschung have now breached this barrier in reaction scope for Brønsted acids using a highly acidic, chiral imidodiphosphorimidate (IDPi) compound (Science 2018, DOI: 10.1126/science.aaq0445). The researchers propose that the substrates—1,1-disubstituted alkenes with pendant alcohols—squeeze into an enzymelike pocket in the catalyst. The stereodefined cavity facilitates a ring-forming reaction to give tetrahydrofuran and tetrahydropyran products in high enantioselectivity. The team additionally reveals one example of an intermolecular version of the reaction, albeit with slightly lower yield and selectivity than its tethered counterpart. This transformation could be the first of many such alkene hydrofunctionalizations, List says.