Functionalization of C(sp 3 )–H bonds using a transient directing group

Amino acids can lend palladium a hand Metals such as rhodium and palladium (Pd) are adept at activating otherwise inert carbon-hydrogen bonds toward useful reactivity. To get properly oriented, they often require some help from oxygen or nitrogen groups nearby. Appending and removing these directing groups, however, detracts from the efficiency of chemical synthesis. Zhang et al. show that amino acids can act as temporary directing groups in the Pd-catalyzed coupling of arenes with aldehydes or ketones. By reversibly binding to these latter substrates just long enough for the Pd catalysis to ensue, the amino acids eliminate the need for more laborious directing group manipulations. Science , this issue p. 252