Fig. 1 |. Approaches to the desymmetrization of methylene units.

a, The desymmetrization of methylene groups by enantioselective C–H activation is a general strategy for the construction of simple tertiary stereocentres. b, The analogous desymmetrization of difluoromethylene groups by enantioselective C–F activation has not been reported so far. c, The cooperation of a chiral, low-valent transition metal complex and a hard fluorophilic activator enables the enantioselective activation of a single C–F bond at an allylic position. FG, functional group; AG, activating group (for example, electron-withdrawing group, aryl group, heteroatom or directing group; few examples lack an activating group); Nu, nucleophile; M, transition metal; OA, oxidative addition.