Metal-Catalyzed Intermolecular Hydrofunctionalization of Allenes: Easy Access to Allylic Structures via the Selective Formation of C–N, C–C, and C–O Bonds

Following a strong regain of interest over the past 20 years in the chemistry of allenes, this "forgotten" family of unsaturated molecules is undergoing a renaissance. In this context, the metal-catalyzed hydrofunctionalization of allenes is nowadays one of the most studied transformations. The latter is of great interest because it opens a way to produce selectively functionalized allylic structures. These motifs are important in synthesis, particularly for the formation of asymmetric centers. Hydrofunctionalization of allenes is also a totally atom economical strategy, avoiding generation of any waste, to produce allylic functionalized structures. Compared to the main pathway to obtain the latter (aka Tsuji-Trost allylic substitution), metal-catalyzed hydrofunctionalization does not require the prefunctionalization of starting material with a leaving group. This review presents a state of the art exploration of all existing transition metal-catalyzed methods allowing the selective intermolecular hydrofunctionalization of allenes with N-H, C-H, and O-H nucleophiles or electrophiles.