Borylation of alkanes goes metal-free

Abstract

Making carbon-boron bonds is useful in organic synthesis, because chemists can convert those borylated compounds into so many other things. Typically, borylating alkane C–H bonds is tricky, because the reaction favors tertiary and secondary C–H bonds, and to get primary C–H bonds to react, chemists need to add transition metal catalysts. When making pharmaceuticals, scientists eventually have to strip out these toxic metals, which can be an arduous process. Varinder Aggarwal and coworkers at the University of Bristol have now found a way to selectively activate primary alkane C–H bonds using light and a chloride-based catalyst ( Nature 2020, DOI: 10.1038/s41586-020-2831-6 ). The group was able to get around 60% yield of clean borylated alkanes under mild conditions. The researchers trigger the reaction with violet light. First, there is an electron transfer from an oxidant, an N -alkoxyphthalimide ester, to the chloride hydrogen atom transfer catalyst. The resulting species then